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The excellent hardness and wear resistance of AlCoCrFeNiMo0.8–TiC composite coating benefit from various strengthening mechanisms, including fine grain strengthening, dislocation strengthening, load transfer strengthening, solid solution strengthening, and precipitation strengthening. To analyze their contributions in the strength and hardness, an accurate prediction model is essential. In this work, a prediction model for the hardness increment was established based on some key elastic constants calculated by the first-principles. Subsequently, the contributions of strengthening mechanisms were quantitatively evaluated by the developed prediction model. It was found that the Young's modulus and shear modulus for B2 phase were 179.65 GPa and 67.36 GPa, respectively, and those of σ phase were 354.08 GPa and 139.19 GPa, respectively. The precipitation strengthening was the predominant mechanism in the composite coating, with a strength contribution of 736.4 MPa and a hardness contribution of 225.2 HV, which accounted for 76.2% of the contribution values. The prediction model has high accuracy, which is evidenced by the small relative error (9.1%) between the total theoretical hardness contribution (295.2 HV) and the Vickers hardness tested by nanoindentation (322.1 HV). The AlCoCrFeNiMo0.8–TiC composite coating has various strengthening mechanisms. To quantitatively analyze these contributions on the hardness, a prediction model is established based on the elastic moduli obtained by the first-principles calculations. [ABSTRACT FROM AUTHOR]

Carbidic austempered ductile iron (CADI) is a new type of wear-resistant material with high performance developed in recent years. The effect of austempered temperature on the microstructure and properties of high B-bearing CADI was investigated. Boron is an element that significantly interferes with the spheroidization process. When the boron content in CADI is high, the crystallization of spheroidal graphite in the as-cast microstructure is hindered, and its roundness, spheroidization rate, and volume fraction are significantly reduced. The results of its heat treatment process show that with the increase of austempered temperature, the volume fraction of residual austenite in the matrix increased, the size of acicular ferrite becomes coarser, and the ferrite also increases significantly, and the macroscopic hardness and wear resistance of the specimens gradually decreased. [ABSTRACT FROM AUTHOR]

This study is to reveal the influence of the amount of carbon content on the microstructure evolution, mechanical properties, and wear properties of Hypereutectic High Chromium Cast Iron (HHCCI). The results indicated that the carbon content plays a key role in the regulation of carbides in the cast iron microstructure. As the amount of carbon content rises, the primary carbides in the cast iron microstructure become apparently coarser, and the volume fraction of carbides gradually increases. The carbide volume fraction reaches 62% when the carbon content is 5 wt.%. When the value of the carbon content increases, the accumulation and growth of eutectic carbides in the heat-treated cast iron become more and more obvious. After heat treatment, a large number of secondary carbides will be precipitated from the austenite matrix, in the form of fine particles or short rods, with a dispersed distribution. The macroscopic hardness of HHCCI has increased. When the carbon content is 3.5 wt.%, the macroscopic hardness is 61.2 HRC, and when the carbon content becomes 5 wt.%, it reaches 64.3 HRC. The wear resistance of HHCCI increases with the value of the carbon content increases. When the carbon content was increased from 3.5 wt.% to 5.0 wt.%, the wear resistance of the material increased by 85.7%. The wear of HHCCI is mainly adhesive wear and fatigue wear, and the wear morphology is mainly spalling pits and wear debris. [ABSTRACT FROM AUTHOR]

Using laser cladding technology, a Ni60A alloy cladding layer added with rare earth oxides CeO2 and Cr3C2 was prepared on the surface of Cr12MoV die steel. Through scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) analyses, the influence of CeO2 on the microstructure, hardness and wear resistance of Ni60A–Cr3C2 laser cladding layer was studied, and the mechanism of action of CeO2 was discussed. The results show that in the laser cladding Ni60A–Cr3C2 coating, after adding CeO2 powder, the cladding layer is well formed and the microstructure is significantly refined. As the addition of CeO2 increases, the microhardness of the cladding layer increases first and then decreases. When the addition amount of CeO2 is 2 wt.%, the microhardness of the coating is the largest, which is 1107 HV. As the content of CeO2 continues to increase, the hardness decreases. As the content of CeO2 in the cladding layer increases, the wear loss of the sample first decreases and then increases. When the mass fraction of CeO2 is 1 wt.%, the wear loss of the cladding layer is the least and the wear resistance is the best. The wear morphology of the Ni60A + Cr3C2 cladding layer without adding CeO2 appears with a lot of abrasive debris, and the main mechanism is adhesive wear. When the addition amount of CeO2 is 1 wt.%, the wear mainly appears as furrow, which denotes abrasive wear. [ABSTRACT FROM AUTHOR]

This work aims to elucidate the microstructure characteristics of each phase in carbidic austempered ductile iron and the nucleation and growth of acicular ferrite in an austempering temperature range of 250–450 °C. The research results showed that the carbides (Fe, Cr)3C obtained by the eutectic reaction had high indentation hardness and indentation modulus, and the interface between acicular ferrite and eutectic carbides belonged to incoherent boundary. Since the nucleation driving force of acicular ferrite increased with an increase in temperature difference (ΔT), the size of acicular ferrite gradually decreased with the decrease in isothermal temperature. When the austempering temperature was above 400 °C, acicular ferrite preferentially nucleated around the graphite nodules and inside grains. However, acicular ferrite preferentially nucleated around the graphite nodules and the eutectic carbides at temperature below 400 °C. Additionally, a fine twin structure had been found inside some acicular ferrite after austempering at a low temperature (250 °C). [ABSTRACT FROM AUTHOR]

• A numerical-experimental method was used to study Ni60A coatings. • The profile of simulated cross-section is good agreement with experiment. • Sharp thermal gradient was generated in the vicinity of heat source. • The maximum difference of viscosity in the molten pool was about 32.8%. • The longitudinal stress and microsegregation increased the crack susceptibility. 3D finite element model (FEM) was built for the simulation of temperature and stress field induced by laser cladding. The proposed model was validated by experimental results. The numerical width and depth of coating matched well with the experimental cross-section of macrograph. The viscosity of molten pool versus the temperature field was also discussed, and the maximum difference of viscosity in different zones was approximately 32.8%. High temperature and sharp thermal gradient was generated in the vicinity of heat source, which was prone to produce residual stress. The heat distribution obtained from temperature field was in consistent with the thermocouple measurements. Due to large plastic tensile deformation of materials, the longitudinal residual stress was susceptible to crack propagation in the laser cladding. The measured maximum value of longitudinal residual stress reached 492 MPa, which was lower than predicts. The coatings were apt to crack along the vertical scanning direction. In addition, the crack susceptibility of coatings was not only depended on residual stress, but also the microsegregation of Cr, Ni and Fe elements. The calculation results are helpful for systematically understanding the melt pool, heat cycles, and stress, which related to laser cladding Ni-based materials. [ABSTRACT FROM AUTHOR]

Abstract Ni-based composite coatings reinforced with in-situ titanium-doped NbC particles were fabricated on Cr12MoV steel plate utilizing laser cladding technology. The microstructure and mechanical properties of the coatings were investigated, as well as the effect of different Nb/Ti mole ratio on the distribution characteristics and formation mechanism of titanium-doped NbC particles. The (Ti, Nb)C distributed homogeneously in the coatings. According to the EBSD results, the coating with Nb/Ti = 1:1 showed strong texture characteristics, and the grains size of the bottom was smaller due to faster heat dissipation. As lower surface energy and lattice misfits of TiC and NbC, (Ti, Nb)C was easily synthesized and the pre-formed TiC particles were the most favorable attachment sites. According to the analysis results of SEM, EPMA and TEM, when Nb/Ti = 1:1, (Ti, Nb)C was a multiple carbide with a NbC structure. In addition, the various morphologies of reinforcing phases were relevant to the solidification rates, temperature gradient and composition distribution. The micro-hardness and wear resistance of coating with Nb/Ti = 1:1 exhibited significantly improvement compared with other coatings. Graphical abstract Unlabelled Image Highlights • The micro-hardness and wear resistance of coating with Nb/Ti = 1:1 exhibited clear improvement. • The (Ti, Nb)C particle in the coating with Nb/Ti = 1:1 exhibited a multiple carbide with a NbC structure. • The coating with Nb/Ti = 1:1 showed strong texture characteristics, and the grains size of the bottom was smaller. • The microstructure evolution mechanism of in-situ titanium-doped NbC reinforced Ni45 coating was studied. [ABSTRACT FROM AUTHOR]

Abstract In this work, the high temperature wear behavior of Ca Ti modified high-boron high-speed steel is investigated. The results indicate that the microstructure of the alloy consists of matrix and eutectic borocarbide. Ca Ti modification aims at improving the stability of borocarbide under wear condition through making the distribution of borocarbide more isolated. The wear experiment revealed that the wear resistance of high-boron high-speed steel is much better than that of T15 steel due to the better oxidization resistance and mechanical property of matrix and borocarbide respectively. Under 25 °C and 200 °C, main wear mechanism of high-boron high-speed steel is adhesive spalling. When the temperature is 400 °C, the mechanism becomes combination of adhesive spalling and oxidization. Under 600 °C, the mechanism is oxidation. Highlights • Borocarbide in Ca Ti modified high boron high speed steel is remarkably refined and spheroidized. • Wear resistance of high boron high speed steel is much better than that of T15 high vanadium high speed steel. • Worn surface roughness of high boron high speed steel after high-load and long-time wear process is quite low. [ABSTRACT FROM AUTHOR]

Abstract As a surface repair and strengthening technology, (Ti, Nb)C/Ni coatings with different amount of CeO 2 were fabricated to repair the automobile dies. The phase constitution, microstructure, texture characteristics of oriented growth, micro-hardness, tensile properties and the action mechanism of CeO 2 were investigated. The results showed that the diffraction peaks of γ-Ni(Fe), (Ti, Nb)C, Cr 7 C 3 and Cr 23 C 6 drifted slightly as a result of solute atoms incorporation. The compact and homogenized microstructure of coatings was dominated by small striped precipitated phases and particles according to SEM and TEM results. The size of (Ti, Nb)C particles were suppressed by rare earth element Ce, which was prone to accumulate at the interface of grain boundary or crystalline phases. The unmelted CeO 2 can also become the heterogeneous nucleation basement of (Ti, Nb)C, Cr 23 C 6 and Cr 7 C 3 particles. EBSD results showed that the grain growth orientation of coatings was changed by the effect of CeO 2 on the fluidity of molten pool, as well as the growth of particles. In addition, the tensile properties of coatings were improved, and the fracture behavior was transformed from the quasi-cleavage fracture to brittle fracture with the increase of CeO 2 addition. Highlights • (Ti, Nb)C/Ni coatings with different amount of CeO 2 addition were fabricated utilizing laser cladding technology. • Proper content of CeO 2 has the effect of improving the microstructure and tensile properties. • The growth orientations of particles in the coatings were perpendicular to laser cladding direction according to the EBSD results. • The action mechanism of rare earth oxides CeO 2 was discussed systematically. [ABSTRACT FROM AUTHOR]

Abstract In this work, the effect of solidification rate on the microstructure and impact toughness of high boron high speed steel is systematically investigated. The theoretical and experimental results indicate that the as-cast microstructure of high boron high speed steel consists of α-Fe matrix and eutectic borocarbide. Without Ca-Ti addition, borocarbide presents a continuous and reticular structure. After Ca-Ti modification, borocarbide possesses an isolated, fine structure. Besides, cooling rate obviously affects the extent of spheroidization. In modified high boron high speed steel, calcium possesses surface activity, which restrains the growth of eutectic borocarbide during solidification. Titanium exists in the form of dispersedly distributed TiC particles which act as heterogeneous nuclei for eutectic borocarbide. The impact toughness of high boron high speed steel is remarkably improved by Ca-Ti modification, which can be further improved by cooling rate. The effect of cooling rate on improving of the toughness can provide a scientific basis for the foundry process designing. [ABSTRACT FROM AUTHOR]

The microstructure evolution, microhardness and wear resistance of Ni45 composite coatings reinforced by in-situ NbC were investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), electron probe microprobe analyzer (EPMA), transmission electron microscopy (TEM), digital microhardness tester and wear test machine. The results showed that the matrix was mainly composed of γ-Ni(Fe) solid solution, and the reinforcement phases consisted of Cr 23 C 6 , NbC, Cr 7 C 3 , Cr 2 B and little content of Cr 3 C 2 . In-situ NbC particles were homogeneous and heterogeneous nucleation from the Nb and C atoms dissolved in the molten pool, which was first precipitated from the Ni45 alloy liquid. With the increase of NbC designed content, the microhardness of coating increased gradually. When the designed content was 20%, in-situ NbC particles were regular and distributed homogeneously, and the composite coating exhibited excellent wear resistance which was higher 4.43 times than that of the original coating. [ABSTRACT FROM AUTHOR]

We prepared the AlCoCrFeNiMo x -TiC coating by laser cladding. With the addition of Mo element, the hardness and wear resistance are improved significantly by the TiC particles and σ phase. [Display omitted] • The AlCoCrFeNiMo x -TiC composite coatings with various Mo are fabricated by laser cladding. • Due to the substitution of Mo atoms, a ring of (Ti, Mo)C phase grows in the outer layer of TiC particles. • (Ti, Mo)C/BCC interface has a lower interfacial energy and a more stable interfacial bonding. • The coating matrix shows a spinodal structure of B2 + σ phase due to the introduction of Mo. • With the increased Mo, the hardness of composite coating increases from 611.9 HV 0.3 to 822.6 HV 0.3. As a typical wear-resistant material, TiC particle-reinforced AlCoCrFeNi composite coatings have great advantages. In this work, the Mo was added to AlCoCrFeNi-TiC coatings to further improve the wear resistance, which were fabricated as AlCoCrFeNiMo x -TiC (x: molar ratio; x = 0, 0.2, 0.5, 0.8) composite coatings by laser cladding. The microstructure evolution, hardness, and wear resistance were investigated in detail. The results show that a ring of (Ti, Mo)C phase is formed in the outer layer of TiC particles due to the substitution of Mo atoms. Based on the first-principles calculations, the lattice constant of (Ti, Mo)C phase is 4.328 Å, slightly smaller than that of TiC. More importantly, Mo can significantly reduce the interface energy from 0.27 J·m−2 to − 0.18 J·m−2, thus improving the interface stability. The coating matrix (CM) exhibits a spinodal structure of B2 + σ phase, caused by the generation of σ phase. The σ phase has a calculated hardness of about 15.3 GPa, which is undoubtedly conducive to wear resistance of the CM. With the addition of Mo, the hardness of composite coating increases from 611.9 HV 0.3 to 822.6 HV 0.3. All the coatings present high wear resistance, as evidenced by the abrasive wear mechanisms. [ABSTRACT FROM AUTHOR]

The microstructure and oxidation kinetics of Fe-B-based alloys at 927 K in air with different boron concentrations of 0.95, 1.45, 2.10, and 3.08 wt% were studied. The alloy microstructures were interpreted to consist of α-Fe, FeB, and pearlite. After 100-h oxidation, the oxides comprised FeO at the surfaces and a mixed BO-SiO layer at matrix/oxide interface. The formation of mixed oxides layer was affected by boron content in the alloy and had obvious influence on the oxide morphology. The isothermal oxidation kinetics at 973 K exhibited initial rapid mass loss followed by slow mass loss, and the oxidation rate constants of the two oxidation stages demonstrated completely opposite tendencies with the increase of boron. The Fe-B 3.08 wt% alloy exhibited the best oxidation resistance after 100 h of cyclic oxidation due to the formation of a well-distributed and continuous BO-SiO mixed oxide layer. [ABSTRACT FROM AUTHOR]

The microstructure and oxidation behavior of Fe–B alloys have been investigated. Oxide scale cross-sectional microstructures oxidized at 1073 K for 100 h have been studied. EPMA investigations show that B 2 O 3 –SiO 2 oxides accumulates in the inner oxide layer which improves the oxidation behavior and oxide layer adhesion considerably. Cyclic oxidation kinetics data indicates that Fe–B 3.08 wt.% alloy presents the best oxidation resistance. The formation of diffusion zone in the Fe–B alloys indicate that the oxidation of the Fe 2 B boride is controlled by boron diffusion. The diffusion zone increases with time and reaches a maximum width of 60–65 μm. [ABSTRACT FROM AUTHOR]

The solidification microstructure, crystallography of eutectic precipitations and mechanical properties of high boron steel with various aluminium and chromium concentrations have been investigated extensively in the present study, as the foundation of the further analysis about the corrosion and abrasion properties at elevated temperature. The experiment results indicate that the as-cast microstructures of test alloys mainly consist of a dendritic matrix with many interdendritic precipitations. The Fe–B binary alloy is mainly composed of ferrite, Fe 2 B and pearlite and the Fe–B–Al ternary alloy consists of α-(Fe, Al) solid solution, Fe 2 B and Fe 3 AlC 0.5 . When aluminium and chromium elements are added synchronously, the as-cast microstructure changes to α-(Fe, Al, Cr) solid solution, (Fe, Cr) 2 B boride, M 7 (C, B) 3 and M 23 (C, B) 6 borocarbides. Moreover, the nucleation and growth of M 7 (C, B) 3 borocarbide is adhere to (Fe, Cr) 2 B boride because of an interphase match between crystal plane (10 1 ( — ) 0) of M 7 (C, B) 3 and (010) of Cr-rich (Fe, Cr) 2 B. Alloy Fe-1.46 wt. % B-0.22 wt. % C-11.92wt. % Cr-8.73 wt. % Al shows the highest impact toughness value. The main fracture mode is brittle fracture of boride and tough fracture of matrix. [ABSTRACT FROM AUTHOR]

Influences of the tempering temperature on the microstructure, mechanical property and wear resistance of High-Boron High Speed Steel (HBHSS) roll materials were investigated by means of optical microscopy, scanning electron microscopy (SEM), X-ray diffraction, hardness measurement, impact tester, tensile tester and pin abrasion tester. The results show that the as-cast structure of HBHSS consists of a great amount of martensite and M2(B,C) and a few retained austenites and M23(B,C)6. After solution treated at 1,050 °C and followed by oil cooling, the amount of M23(B,C)6 carbo-borides in quenched HBHSS increases obviously and the macrohardness of the quenched HBHSS is 66 HRC, which is very close to the 65.8 HRC of as-cast HBHSS. On the whole, the hardness of HBHSS alloy shows a trend of slight decrease with increasing tempering temperature when tempered below 500 °C. While when above 500 °C, the hardness increases slightly as the tempering temperature increases and reaches a peak at 525 °C and then decreases obviously. The impact toughness of HBHSS has a tendency to increase as the tempering temperature increases. Tempering can improve the tensile strength and elongation of HBHSS, but a higher tempering temperature causes a slight decrease in both tensile strength and elongation. Excellent wear resistance can be obtained by tempering at 500 to 550 °C. [ABSTRACT FROM AUTHOR]

Abstract: Segregation influences the microstructure and performance of high speed steel (HSS) roll. The main reason why segregation occurs in centrifugal cast HSS roll is that atom clusters are formed in HSS melt and such atom clusters have different densities. The high-density atom clusters move to the outer periphery and the low-density atom clusters move to the inner periphery of the roll under centrifugal force. Changing the movement law of atom clusters in the centrifugal force field and increasing the solidification rate of HSS melt can lighten the segregation in HSS roll and improve its performance. [Copyright &y& Elsevier]

Abstract: The effects of roll materials, mould parameter, pouring parameter and cooling parameter on the crack of a high-speed steel (HSS) roll, which is manufactured by means of centrifugal casting, are investigated. The improvement of the HSS roll is effectively achieved through the addition of suitable amounts of potassium and rare earth (RE). The hot tearing force (i.e. the resistance to hot tearing) of the modified HSS roll is increased by 32.77% and reaches 158N, while the line constriction (i.e. the solidification constriction of the HSS in unit distance) is decreased. In addition, the temperature field and stress field of the roll can be improved by adopting variable-speed centrifugal casting, variable-flux pouring and variable-speed solidification cooling techniques, which help to improve the filling and solidification of the molten steel and eliminate the cracks. [Copyright &y& Elsevier]

Abstract: A new type of wear resistant low carbon Fe–B cast steel with granular borides can be obtained by alloying with titanium and cerium rare earth (RE). As a result, the as-cast eutectic boride structures of Fe–B cast steel are greatly refined and a blocky, less interconnected boride network is obtained from continuous ledeburite. After heat treatment, the boride eutectic in the modified Fe–B cast steel is in the form of a granular boride structure that appears to be isolated particles The guide rollers made of modified low carbon Fe–B cast steel show excellent wear resistance and thermal fatigue resistance in high speed wire mills. [Copyright &y& Elsevier]

Abstract: Solidification microstructure of a cast stainless steel containing 1.5–2.5 wt.%B has been examined by means of the optical microscopy (OM), the scanning electron microscopy (SEM), the electron probe microanalyzer (EPMA), energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD) and Vickers microhardness. The as-cast microstructure consists of the M2(B,C) borocarbide and the austenite. The borocarbide is continuously distributed over the austenite. There are some broken-networks in the local location of borocarbide. Moreover, the distribution of alloy elements is not homogeneous in the cast B-bearing stainless steel. Boron element is mainly distributed over the borocarbide, carbon element is mainly distributed over the matrix. Chromium element is mainly distributed over the borocarbide, and there are also some chromium elements in the matrix. Nickel element is mainly distributed over the matrix and silicon is insoluble in the borocarbide. [Copyright &y& Elsevier]

Abstract: In this study ceramic-lined compound copper pipe (CLCCP) was produced by self-propagating high-temperature synthesis (SHS) and centrifugal casting technology. The effects of additives such as SiO2, CrO3, Na2B4O7 and ZrO2 on the densification degree, combining strength and the toughness of the ceramic layer were of prime interest. The results show that the densification degree of the ceramic layer can be improved by adding SiO2 and CrO3 in the thermite. This improvement correlated with the reduction of porosity of ceramic layer. The combining strength is increased through the addition of a suitable amount of Na2B4O7. The highest fracture toughness of ceramic layer is obtained at 7 wt.% of ZrO2 in thermite. The CLCCP shows excellent service properties when it is used in tubular billet crystallizer, including the prevention of cracks and flakes. [Copyright &y& Elsevier]

Abstract: The effect of heat treatment on the performances of multi-element low alloy wear-resistant steel (MLAWS), which is used to make the rolling mill torii liner, was investigated. The results show that the hardness and tensile strength increase as the quenching temperature is increased from 840 to 900°C. However, the hardness decreases rapidly as the quenching temperature is increased beyond 900°C, while the temperature has little influence on the tensile strength when it exceeds 900°C. No clear influence on the impact toughness has been observed unless the quenching temperature is beyond 920°C. As the tempering temperature exceeds 300°C, tiny ɛ carbides separate out from martensite and bainite complex structures and cause the carbon content in the complex structures to decrease. This results in the toughness to increase significantly. The best wear resistance can be obtained by tempering at 350°C. The optimum heat treatment of MLAWS comprises quenching at 900–920°C and tempering at 350–370°C. [Copyright &y& Elsevier]

Abstract: The effects of rare earth (RE) on the microstructures and properties of the Fe–5% V–5% W–5% Mo–5% Cr–3% Nb–2% Co–2% C (Fe–V–W–Mo) alloy are investigated. Modification of the Fe–V–W–Mo alloy is effectively achieved through the addition of suitable amount of RE, which refines the prior-austenite grains and eutectic structure. The as-cast microstructure shows that the flake carbides in the eutectic structure become short and fine. After hardening treatment, most of the eutectic carbides are spheroidized and uniformly distributed. The hardness and hot hardness of the modified Fe–V–W–Mo alloy are slightly increased, while the impact toughness is increased by 37.81% and reaches 10.17J/cm2. The rolls made of modified Fe–V–W–Mo alloy show excellent service properties in high speed wire mills, including the prevention of cracks and spalling. [Copyright &y& Elsevier]

Wire-arc sprayed Al-based composite coatings attracted great attentions due to their prospective application in offshore engineering. However, the difficulty in regulating ceramic reinforcements limited the performance of these coatings. In this work, we proposed a novel rotary swaging (RS) process to improve the deposition of ceramic particles, thus the Al/Al 2 O 3 composite coating was prepared and evaluated in comparison with the traditional coating by spraying the drawing cored wires. As expected, the RS process promotes the melt of Al 2 O 3 particles, leading to a significant increase of their deposition fraction with the simultaneous improvement in coating compactness and the interfacial bonding of heterogeneous splats. The sufficient melt of Al 2 O 3 particles is attributed to the enhanced cohesion strength of filled powders to bear the vibration of arc force and facilitate heat transport. The explored composite coating displays a superior corrosion resistance in 3.5 wt% NaCl aqueous solution, due to the reduced active area on electrode surface and the lower sensitivity to pitting. Benefiting from a dynamic self-reinforcing effect, the explored composite coating presents lower coefficient of friction and significantly enhanced wear resistance under dry frictional condition. The present results demonstrate a great potential of the developed Al/Al 2 O 3 composite coating in offshore application and provide an inspiration for future works aiming to exploit the high-performance metal-matrix composite coatings synthesized by low-cost wire-arc spraying. • The rotary swaging process improved the melt and deposition of Al 2 O 3 particles. • The improved oxide film enhanced the corrosion resistance of composite coating. • The dynamic self-reinforcing effect enhanced the wear resistance of composite coating. [ABSTRACT FROM AUTHOR]

In this work, different contents of Cu were added into carbidic austempered ductile iron (CADI) to improve the corrosion resistance and the corrosive wear resistance. Microstructures of CADI have been systematically investigated by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), atomic force microscope (AFM). The results showed that with the addition of Cu elements, the thickness of bainitic ferrite plates and the potential difference (ΔU matix- graphite nodules and ΔU matix- carbides) were reduced significantly. The effect of Cu on the corrosion resistance and the corrosive wear resistance has been studied by an electrochemical workstation and two kinds of corrosive wear tester. In addition, worn surfaces and corroded surfaces of the samples have been examined by SEM, 3D laser scanning microscope and X-ray photoelectron spectroscopy (XPS). As the Cu content increased, the corrosion resistance of CADI under acidic condition increased. When the Cu content was 1 wt%, both corrosive wear resistance without load under alkaline condition and corrosive wear resistance with load under alkaline and acidic condition were optimal. Nevertheless, under acidic condition, the corrosive wear resistance without load of CADI with 1.5 wt% Cu was optimal. • Electrochemical potentials of CADI's microstructural components are: U graphite > U carbides > U matrix. • Cu element is mainly distributed in the retained austenite. • The corrosion resistance of CADI can be improved by adding Cu element. • Corrosive wear resistance of CADI with 1 wt% Cu is significantly better than that of Cu-free CADI. [ABSTRACT FROM AUTHOR]

The microstructure evolution of boron-bearing high speed steel roll materials after casting and tempering was investigated. The results indicate that as-cast boron-bearing high speed steel consists of martensitic matrix, retained austenite and different borocarbides. The as-cast alloy has a hardness above 64 hRC, and the borocarbides distribute along the grain boundaries. after Re-Mg-Ti compound modification treatment, obvious necking and broken network appear in the grain boundaries. The hardness of boron-bearing high speed steel roll materials reduces gradually with the increase of tempering temperature. under the same conditions, the toughness of the modified roll material is higher than that of the unmodified roll material. Wear tests show that the wear resistance of boron-bearing high-speed steel modified by Re-Mg-Ti compound modification treatment is better. [ABSTRACT FROM AUTHOR]

(Ti, Nb)C particles reinforced Ni45 coatings were made by a fiber laser system. The atomic structure, interfacial stability, interfacial fracture toughness, electronic structure and bonding nature of γ-Ni/(Ti, Nb)C were systematically analyzed using first principles calculations. TEM results showed that the interface orientation relationship of γ-Ni/(Ti, Nb)C was [0 1 ¯ 0](202)//[00 1 ¯ ](220). For the γ-Ni/(Ti, Nb)C interfaces, the stacking sites have much influence than the substitution position of Ti, the center-site stacking interfaces shower higher adhesion work and lower interface energy, indicating the interfacial alloying or new phases were prone to formed. According to the interfacial fracture toughness results, the mechanical failure of γ-Ni/(Ti, Nb)C may initiate at the interface or close to γ-Ni rather than (Ti, Nb)C. The bonding behavior of γ-Ni/(Ti, Nb)C was a blend of covalent bond and partial ionic bond. The chemical bonding properties of interfacial atoms were also discussed in view of electronic structure and partial density of states (PDOS) results. Unlabelled Image • Interface orientation relationship of γ-Ni/(Ti, Nb)C was [0 1 ¯ 0](202)//[00 1 ¯ ](220). • The center-site stacking interfaces shower higher adhesion work and lower interface energy. • Mechanical failure of γ-Ni/(Ti, Nb)C may initiate at the interface or close to γ-Ni. • Bonding behavior of γ-Ni/(Ti, Nb)C was a mixture of covalent bond and partial ionic bond. [ABSTRACT FROM AUTHOR]

The austenite homogenization of carbidic austempered ductile iron is studied from both thermodynamics and dynamics by calculation and experimentation, and a mathematical model of carbide dissolution is established to predict the dissolved quantity of carbides. The results indicate that the mass fraction of carbon in austenite (austenite–graphite stable equilibrium) calculated by the Thermo‐Calc software is similar to the results quantitatively analyzed by electron probe. Based on Fick's second law, the elemental diffusion kinetics is analyzed by MATLAB software. Because the diffusion rate of chromium in austenite is lower than carbon, the carbon content is significantly decreased around undissolved carbides, but the chromium content is still high. Two equations of undissolved carbides' area are obtained by linear fitting. [ABSTRACT FROM AUTHOR]

The effects of silicon alloying and heat treatment on the microstructure and properties of Fe-35Cr-4C-xSi (x = 0.5, 1.2, 19, 2.6) hypereutectic high-chromium cast iron (HHCCI) were explored through first-principles calculations and phase diagram calculations combined with XRD, SEM, TEM and other methods. With the increase of Si content, the matrix structure of HHCCI transforms from martensite to ferrite. The phase diagram analysis reveals that higher silicon content results in elevated austenite transformation initiation temperatures, reduced austenite phase areas, and expanded ferrite phase regions. Additionally, the study calculates the diffusion activation energy of C atoms within silicon-bearing and silicon-free HHCCI matrices, providing valuable insights into the role of silicon in promoting the transformation of the HHCCI matrix into ferrite. Notably, silicon facilitates the diffusion of C atoms into the silicon-bearing HHCCI matrix, thereby preventing complete austenitization. After ultra-high-temperature heat treatment, the matrix structure of high-silicon HHCCI (1.9 wt.% Si) can be transformed from ferrite to martensite. With the increase of Si content, the corrosive wear resistance of HHCCI increases first and then decreases. The 1.9Si HHCCI after ultra-high-temperature heat treatment exhibits the best corrosive wear resistance in both acidic and alkaline corrosive wear environments, and the silicon-bearing HHCCI is more resistant to alkaline corrosive wear. This study reveals promising applications of silicon-bearing HHCCI in industries such as hydraulics and coal mining, particularly as a material for making slurry pumps. Notably, in comparison with previous work by our research group, this study delves deeper into the mechanisms underlying the structural and performance changes of silicon-bearing HHCCI due to heat treatment and silicon content variation. [ABSTRACT FROM AUTHOR]

In this paper, the effects of different quenching holding times on the microstructure and properties of high-silicon hypereutectic high-chromium cast iron (Fe–4.0C–35.0Cr–1.9Si) were investigated. The effect of quenching holding time on the microstructure of high silicon hypereutectic high chromium cast iron was analyzed by optical microscope, scanning electron microscope and X-ray diffractometer. The hardness and wear resistance of high-silicon hypereutectic high-chromium cast iron quenched at 1150∘C for different time were tested by Rockwell hardness tester, microhardness tester and wear tester. The results show that the microstructure of as-cast high-silicon hypereutectic high-chromium cast iron is mainly composed of pearlite matrix and M7C3 carbide. Quenching heat treatment makes part of the matrix transform from pearlite to martensite, and precipitate a small amount of M 2 3 C6 type secondary carbide. With the increase of quenching holding time from 1 h to 6 h, the amount of martensite transformation gradually increases, the primary carbide has no obvious change, the eutectic carbide tip dissolves, and the morphology gradually becomes smooth. The hardness and wear resistance both increase first and then decrease. After 4 hours of insulation, the hardness reaches the highest 60.5HRC, which is increased by 3 HRC compared to 1 hour of insulation. The wear resistance increases by 22.1% compared to 1 hour of insulation. At this time, the wear resistance is the best. [ABSTRACT FROM AUTHOR]

Abstract Based on cold metal transfer (CMT) welding, wire-arc additive manufacturing (WAAM) technology was adopted to manufacture 2Cr13 part. The spatial periodicity of the microstructural evolution and the anti-indentation properties was explored. The results show that the as-deposited part was featured by periodic martensite laths within the block-shaped ferrite matrix in the inner layers, followed by epitaxial ferrite grains containing ultra-fine acicular martensite in the top layer only. A slightly decreased Fe intensity was caused by local elemental segregation during the re-melting process; the homogeneity of Fe and Cr was attributed to similar cooling conditions in the top layer. The martensite size gradually coarsened from the fine grain zone to the coarse grain zone and the shape transformed correspondingly from irregularly short bar-like to orderly long rod-like due to the location-related thermal history. Elongated ferrite grains exhibited a slight fiber texture in the top layer and a random crystallographic orientation in the middle region. The anti-indentation properties evolved periodically due to the periodic microstructural characteristics. The obtained experimental results confirmed higher anti-indentation properties of the as-deposited part following comparison with the as-annealed base metal, while the elastic moduli of samples were not significantly different. Graphical abstract Unlabelled Image Highlights • 2Cr13 thin-wall part with defect-free was additively manufactured by robot-assisted CMT technology. • Martensite coarsened gradually from FZ to CZ while only ultra-fine acicular martensite in the top layer. • A random crystallographic orientation in the middle region while a slightly fiber texture in the top layer • Mechanical properties were evolved periodically due to the periodic microstructural evolution. [ABSTRACT FROM AUTHOR]

The effects of erosion angle and Fe 2 B orientation on cavitation erosion and interface structures of a directionally solidified (DS) Fe-B alloy in flowing liquid zinc were investigated to clarify erosion mechanism of liquid metal. The results indicate that the cavitation erosion rate of DS Fe-B alloy with Fe 2 B [001] orientation vertical to interface exhibits better erosion cavitation resistance. Erosion angle can strongly affect erosion performance that depends not only on interfacial orientation structure but also on local microturbulence. Erosion morphologies manifest that an obvious cavitation erosion occurs in strong flowing zinc disturbed and agitated zone, which results in severe cavitation pits and slip deformation of products, thus stimulating subsequent localized corrosion and pit-aggregation cracks. Cavitation erosion craters coupled with performance variations confirm that microturbulence-assisted fluid eddies and backflow are responsible for the cavitation pits. The combined effects of flow pattern and interface orientation significantly govern the epitaxial grown ζ removal/accumulation behaviors and multiphase pinning film adhesion. A model of hydraulic liquid-hammer action by cavitation-induced microjet and interface orientation interaction is proposed and discussed to account for cavitation pits and slip cracking, which reveals underlying erosion mechanism and material design of DS Fe-B alloy in flowing liquid zinc. [ABSTRACT FROM AUTHOR]

Mo alloying Fe-based coating was fabricated on the surface of Q235 steel by using 6 kW fiber laser. The effects of Mo additions on the microstructure, microhardness and wear resistance of the cladding layer were studied by means of optical microscopy (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), Vickers hardness tester and M-200 ring block wear tester. Research results showed that the microstructure of Mo-free cladding layer mainly consisted of matrix and eutectic structure. The matrix was martensite and retained austenite. The eutectic structure mainly consisted of M2(B,C) and M7(C,B)3 type of eutectic borocarbides. With the increase of Mo content, there was no significant change in the matrix. However, the eutectic structure was transformed from M2(B,C)- and M7(C,B)3-type borocarbides into M2(B,C)-, M7(C,B)3- and M23(C,B)6-type borocarbides. When the content of Mo is 4.0 wt.%, the Mo2C-type carbide appear on the matrix, and parts of the borocarbide networks are broken. The change of microhardness of the cladding layer was not obvious with the increase of Mo content. But the increase of Mo content increases the wear resistance of the cladding layer. The wear resistance of cladding layer with 4.0 wt.% Mo is 2.4 times as much as the cladding layer which is Mo-free. [ABSTRACT FROM AUTHOR]

The corrosion-wear behavior of Fe-3.5 wt.%B steel in liquid zinc was investigated via the block-against-ring technique. Owing to the protective ability of the Fe 2 B phase, this steel exhibited better corrosion-wear resistance than a 316L stainless steel. SEM, XRD, and EDS of the corrosion-wear interface indicated that the corrosion-wear process of Fe-3.5 wt.%B steel consists of the following steps: corrosion of the matrix, fragmentation and removal of FeZn 13 , and failure of the Fe 2 B. The intensified mechanical effect of wear resulted in significant deterioration (via fracture and removal of FeZn 13 , and spallation Fe 2 B) of corrosion-wear interface, which exacerbated corrosion, and facilitated the corrosion-wear process. [ABSTRACT FROM AUTHOR]

The properties of sulfides are important in the design of new iron-steel materials. In this study, first-principles calculations were used to estimate the structural stability, mechanical properties, electronic structures and thermal properties of XS (X = Ti, V, Cr, Mn, Fe, Co, Ni) binary compounds. The results reveal that these XS binary compounds are thermodynamically stable, because their formation enthalpy is negative. The elastic constants, C i j , and moduli ( B , G , E ) were investigated using stress–strain and Voigt–Reuss–Hill approximation, respectively. The sulfide anisotropy was discussed from an anisotropic index and three-dimensional surface contours. The electronic structures reveal that the bonding characteristics of the XS compounds are a mixture of metallic and covalent bonds. Using a quasi-harmonic Debye approximation, the heat capacity at constant pressure and constant volume was estimated. NiS possesses the largest C P and C V of the sulfides. [ABSTRACT FROM AUTHOR]

This work aims at studying the wear properties of titanium microalloying Carbidic Austempered Ductile Iron (CADI) and the refining mechanism of TiC on M 3 C carbides by theoretical calculation and experimental analysis. The wear tests were carried out by a wet rubber wheel wear tester. Computed results showed that TiC particles could precipitate previously in melt to refine the M 3 C eutectic carbides, and M 3 C (010)/TiC (011) interface is stable. Experimental results showed that TiC particles were formed. The shape of M 3 C eutectic carbides changed from net-like to strip-like after titanium microalloying, which improved the wear resistance of CADI. For CADI, the strip-like or dot-like carbides could protect the matrix more effectively than net-like due to the decrease of exfoliation. [Display omitted] • TiC particles precipitated preferentially during the solidification after titanium microalloying. • M 3 C (010)/TiC (011) interface is stable. • The wear resistance of CADI under acidic conditions was improved after titanium microalloying. • For CADI, the strip-like or dot-like carbides could protect the matrix more effectively than net-like. • The austempering temperature is more dominant in reducing abrasive wear than titanium microalloying. [ABSTRACT FROM AUTHOR]

Highlights • Crack-free 2Cr13 part was additively manufactured using cold metal transfer technology. • Short inter-layer dwelling time induced homogenous microstructural evolution and anti-indentation performance. • Long inter-layer dwelling time caused periodic microstructural feature and anti-indentation property. • A particular part with active-controlled microstructures was fabricated through a single material deposition. Abstract The phase constitution, the microstructural growth behavior, and the anti-indentation performance of 2Cr13 thin-wall part were successfully tailored through inter-layer dwelling time alteration using cold metal transfer (CMT) technology. The short inter-layer dwelling time induced the presence of a low amount of γ-Fe phase, as well as extremely elongated ferrite grains containing ultrafine needle-shaped martensite throughout the entire part. This finally led to a narrow fluctuation in microhardness. The long dwelling time contributed to the α-Fe phase formation only and a periodic microhardness trendline, which was related to a periodic microstructure featured by martensite laths within the block-shaped ferrite matrix. This method, in an intentional manner, could be adopted to manufacture a particular component with local properties that are altered with location through a single material deposition. [ABSTRACT FROM AUTHOR]

Isothermal-compression tests of B4Cp/6063Al composites containing 20 vol.% B4C were performed using a Gleeble-3500 device, at strain rates ranging from 0.001 s−1 to 1 s−1 and deformation temperatures ranging from 723 K to 823 K. The results showed that the high-temperature flow stress of B4Cp/6063Al composites increases with the decrease in deformation temperature or the increase in the strain rate. After friction correction, the friction corrected stress was less than the original experimental stress. At the initial stage of deformation, the difference between the rheological stress after friction correction and the measured rheological stress is small, but with the continuous increase in the strain, the difference between the rheological stress after friction correction and the measured rheological stress is grows. Under the same strain, the difference between the rheological stress before and after friction correction becomes more significant with the decrease in the deformation temperature and the increase in the strain rate. Next, the material constants (i.e., α, β, Q, A, n) of B4Cp/6063Al composites were calibrated based on the experimental data, and a constitutive equation was established based on Arrhenius theory. The experimental values and predicted values of the stress–strain curves are in good agreement with the stress–strain curves of the finite element simulation, and the validity of the constitutive equation was verified. [ABSTRACT FROM AUTHOR]

The zirconium alloy cladding tube and end plug used for nuclear fuel rods are usually joined by pressure resistance welding. And the service performance of the fuel rod cladding is directly influenced by the welded joint. In order to understand the forming process deeply, an axisymmetric electro-thermal–mechanical process finite element model was established in this paper. The current density distribution, temperature field evolution, and joint forming process during pressure resistance welding were all simulated by this model. It was shown that due to the contact resistance, a concentrated heat flow was rapidly generated on the tube-plug contact surface caused by welding current. A heat conduction was established on both sides of the welding surface. The high-temperature region on the side of the cladding tube was larger than the end plug. The metal of the tube extruded to both inside and outside of the joint under the coupled loading of heat and pressure. The location of the highest instant temperature on the welding surface moved from the inside to the outside of the joint. The highest temperature was 1568 °C, not reaching the melting point of zirconium alloy. The joining area and the highest temperature increased with welding current increasing, the welding time had little effect on them. Based on the numerical model, two structural design schemes to improve the joint forming quality were proposed. They were expected to provide a guide line for the joint design. [ABSTRACT FROM AUTHOR]

Coarse TiB 2 , fine TiB and NiTi/NiTi 2 reinforced titanium matrix composite coatings with part of the network-like structure reinforcement distribution were prepared by laser cladding on Ti–6Al–4V alloy using premixed Ni, coarse TiB 2 , fine TiB 2 and Ti powder. The amount and the size of coarse TiB 2 were decreased with increasing distance from the surface. The network-like structure was mainly consisted of NiTi and Ni 3 Ti, and the characteristic of network-like structure gradually became clearer from the top to the bottom. The micro-hardness of the coating was first decreased abruptly and then decreased gradually with increasing distance from the surface, but fracture toughness of the coating was first decreased and then increased. The fracture toughness of the coating can be improved through the crack deflection and the bifurcation, but the crack deflection and the bifurcation were random. [ABSTRACT FROM AUTHOR]

Self-piercing riveting (SPR) has been used to join similar and dissimilar materials for vehicle body application. In order to understand the failure mechanism and develop a method to estimate the shear strength of SPR similar and dissimilar materials, finite element modeling was conducted in this study. In the modeling, the contact conditions between the rivet and the workpieces were taken into account to establish the failure criteria of SPR of steel and aluminum sheets. It was found that the failure procedure of riveted dissimilar materials was different from that of riveted similar materials. Furthermore, the experiments were conducted to validate the modeling results. It was shown that the shear strength and failure mode of SPR joints were in agreement with the modeling results. These results suggested that the model could be used to estimate the shear strength of SPR joints. The factors influencing the failure mode and shear strength of SPR joints were discussed in detail. For rivet pull-out mode, the rivet open angle at the upper sheet, friction coefficient between the rivet and sheet, and the yield strength of the substrate were the key factors. For sheet tearing mode, failure occurred at the weaker sheet and the shear strengths mainly depended on the sheet gage and strength grade of the weaker sheet. [ABSTRACT FROM AUTHOR]

We prepare in-situ TiC reinforced AlCoCrFeNi-based coatings by laser cladding. The in-situ TiC particles improve significantly the hardness and wear resistance of AlCoCrFeNi high entropy alloy coatings. [Display omitted] • The in-situ reinforced TiC particles are synthesized in the AlCoCrFeNi-based high entropy alloy coatings by laser cladding. • The microstructure of composite coatings is mainly composed of the BCC and TiC phases. • The AlCoCrFeNi-20% TiC coating exhibits the best wear resistance with an average hardness of 684.4 HV 0.3. • The hardness of TiC is analysed by the first-principles calculations. High-entropy alloy (HEA) coatings of AlCoCrFeNi are being investigated as potential wear-resistance materials due to their excellent hardness and wear resistance. In this work, AlCoCrFeNi-based coatings were reinforced by in-situ TiC particles via laser cladding. The microstructure and wear resistance were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and wear resistance tests. In addition, the hardness of oxidation TiC particles was analyzed by first principles calculations. The results show that the dominant phase of AlCoCrFeNi-based coatings is BCC phase. In-situ TiC particles present a flower-shaped morphology with Al 2 O 3 core. Based on the calculated hardness, the hardness of TiC decreases with the increase of oxygen atoms in TiC. The hardness and wear resistance are improved considerably with the generation of the in-situ TiC particles. The AlCoCrFeNi-20% TiC coating exhibits the best wear resistance with an average hardness of 684.4 HV 0.3 , and the main wear mechanism is abrasive wear. [ABSTRACT FROM AUTHOR]

The effect of the element cerium on the microstructure and wear behavior of Fe-B cast alloy was investigated by scanning electron microscope, transmission electron microscope, X-ray diffraction analysis, Leica digital image analysis, hardness tester and abrasion tester. The microstructures of as-cast Fe-B alloy are composed of the phase ferrite, pearlite and eutectic boride. Moreover, the as-cast eutectic boride structures in Fe-B alloy containing cerium are finer than that in the alloy having no cerium. After heat treatment, the average boride area and wear weight loss of the alloy containing cerium are lower than these of the alloy having no cerium. Before the formation of primary austenite, cerium can combine with oxygen to form CeO. CeO can act as nuclei of primary austenite, promoting the refinement of austenite and borides during solidification, and improve the wear property of Fe-B alloy. [ABSTRACT FROM AUTHOR]

Over the past decade, researchers have demonstrated much interest in laser cladded metal matrix composite coatings for its good wear resistance, corrosion resistance, and high temperature properties. In this paper, in-situ (Ti, Nb)C particle reinforced Fe-based composite coatings were produced by laser cladding. The effects of Ti/Nb(atomic ratio) in the cladding powder on the formation mechanism and distribution characteristics of multiple particle were investigated. The results showed that when Ti/Nb > 1, Ti had a stronger ability to bond with C compared with Nb. (Ti, Nb)C multiple particles with TiC core formed in the molten pool. With the decrease of Ti/Nb, core-shell structure disappeared, the structure of particle got close to that of NbC gradually. It is found that the amount, area ratio and distribution of the reinforced particle in the coating containing Ti and Nb elements were improved, compared with these in the coating containing equal Nb element. When Ti/Nb = 1, the effects above-mentioned is most prominent, and the wear resistance of the coating is promoted obviously. [ABSTRACT FROM AUTHOR]

Purpose: In this research, the highly dense bulk Cu-5Sn alloy specimens were fabricated using selective laser melting (SLM). This study aims to establish the relationship between laser power (LP), scanning speed (SS) and hatch space (HS) with surface roughness (Ra) and density. To obtain Cu-5Sn alloy formed parts with high strength and low surface roughness. The microstructure and mechanical properties of SLMed Cu-5Sn were investigated. Design/methodology/approach: The relative density (RD) was optimized using the response surface method (RSM) and analysis of variance. First, the Ra of SLMed formed specimens was studied to optimize the forming process parameters with a good surface. Then, the dense specimens were studied by ANOVA and the RSM to obtain dense specimens for mechanical property analysis. Findings: Dense specimens were obtained by RSM and ANOVA. The tensile properties were compared with the casted specimens. The yield and ultimate strengths increased from 71 and 131 MPa for the cast specimens to 334 and 489 MPa for the SLMed specimens, respectively. The ductility increased significantly from 11% to 23%, due to the refined microstructure of the SLMed specimens, as well as the formation of many twin crystals. Originality/value: The Ra, RD and mechanical properties of SLM specimens Cu-5Sn were systematically studied, and the influencing factors were analyzed together. This study provides a theoretical and practical example to improve the surface quality and RD. [ABSTRACT FROM AUTHOR]

In the present study, the microstructure and mechanical properties of cast Fe-10Cr-1.5B (FCB) alloy after different heat treatments were studied. The results showed that the as-cast microstructure of FCB alloy consists of a-Fe, M(M=Cr, Fe, Mn)2(B, C) and M(M=Cr, Fe, Mn)7(C, B)3 type borocarbides, and small amounts of pearlite and austenite. After oil quenching treatment, metal matrix transformed into the martensite from the mixture of martensite, pearlite and austenite. There are many M(M=Cr,Fe,Mn)23(C,B)6 type borocarbide precipitates in the metal matrix, and eutectic borocarbide appears with an apparent disconnection and isolated phenomenon. When the quenching temperature reaches 1,050 °C, the hardness of FCB alloy is the highest, but the change of quenching temperature has no obvious effect on impact toughness of FCB alloy. After tempering, the eutectic microstructure of FCB alloy appears with a "two links" trend. With the increase of tempering temperature, the hardness of FCB alloy decreases gradually and impact toughness increases gradually. Cast FCB alloy oil-quenched from 1,050 °C and tempered from 200 °C has excellent combined properties; its hardness and impact toughness are 61.5 HRC and 8.8 J•cm-2 respectively. [ABSTRACT FROM AUTHOR]

Abstract: Over the past decade, researchers have demonstrated much interest in laser cladded metal matrix composite coatings for its good wear resistance, corrosion resistance and high temperature properties. The effects of RE on the microstructure and properties of laser coatings have also got more and more attention. In this paper, in situ Fe-NbC composite coatings with different CeO2 addition were produced on die steel by laser cladding. The formation mechanism of NbC particles was analyzed. The effects of RE on microstructure and micro-hardness of coatings were investigated. It was revealed that larger NbC particles with hard edges formed around Nb particles, and smaller flocculent NbC particles formed by the chemical reaction of Nb and solid graphite in the molten pool. CeO2 plays important roles in reducing micro-porosities, refining grains, and improving the precipitation of NbC. Therefore, the average micro-hardness and its smoothness from the top to the bottom of the coating were improved after adding CeO2. [Copyright &y& Elsevier]

Highlights: [•] The as-received microstructure of bulk Fe2B comprises iron and silicon borides. [•] The orientation of Fe2B in liquid zinc strongly affects on corrosion resistance. [•] The Fe2B/FeB phase transition process of bulk Fe2B in liquid zinc occurs. [•] Phase transition and spalling dominate corrosion of Fe2B in liquid zinc. [Copyright &y& Elsevier]

• The H13 steel block were prepared by wire arc additive manufacturing. • The microstructure was studied in detail. • The tensile strength and elongation were studied. • The internal information related to micropores is studied. • The reason of the low elongation of printing block is deduced. The H13 steel block was successfully prepared by cold metal transfer(CMT) wire-arc additive manufacturing(WAAM) method. The microstructure characteristics and mechanical properties of the printed block were both studied by experiments. It was found that there were obvious difference in the microstructure and mechanical properties between the central part and overlapping parts of the printed block. It was shown from the microstructure observation that the printed block was mainly composed of martensite and residual austenite. There was an obvious primary austenite grain boundary observed in the base phase. In addition, compared with the overlapping part, the content of residual austenite in the central part was lower. It was shown that the average value of the microhardness in the central part was 596HV, while it was 534HV for the overlapping part due to the higher content of residual austenite. Tensile tests were conducted for different direction of the printed block. Micropores with a volume of 100–400 μm3 were observed in the printed block, with 90 % of the micropores in the range of 100–200 μm3 in volume. The micropores were uniformly distributed in the sample. The presence of micropores leads to the low elongation and tensile strength. [ABSTRACT FROM AUTHOR]