Search

The microstructure and mechanical properties of three kinds of low-carbon medium-manganese steels with different Si contents under an intercritical heat treatment process were studied. The results show that the microstructure of the test forged steel is mainly composed of ferrite and pearlite. After 900 °C complete austenitizing quenching + 720 °C intercritical quenching, the microstructure of the test steel is mainly composed of ferrite and martensite. With the increase in Si content, the microstructure becomes finer and more uniform. The microstructure of the test steel after 900 °C complete austenitizing quenching + 720 °C intercritical quenching + 680 °C intercritical tempering is dominated by ferrite and tempered martensite, with a small amount of retained austenite and cementite. As the Si content increases, the boundaries between ferrite and tempered martensite become more clear. The tensile strength and hardness of the test steel increase with the increase in Si content, while the elongation first increases and then decreases; the comprehensive performance of the test steel is the best when the Si content is 0.685 wt. %, with a tensile strength of 726 MPa, a yield ratio of only 0.65, the highest elongation of 30.5%, and the highest strong plastic product of 22,143 MPa.%. [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 situ NbC-reinforced laser cladding Ni45 coatings have the advantages of high bond strengths, low dilution rates, small heat-affected zones and good wear resistance and have broad application prospects in the field of surface strengthening and repair of workpieces such as automotive molds and engine turbines. Previous studies have mostly used pure niobium powder for in situ synthesis to prepare Ni-based NbC coatings with a high production cost. In this paper, NbC was successfully synthesized in situ in Ni45 powder using inexpensive FeNb65 and Cr3C2. The prepared coating has a uniform microstructure and excellent wear resistance, and the reinforced phases are mainly NbC and Cr23C6. Coating 4# with 25 wt.% FeNb65 + Cr3C2 has the highest microhardness of 776.3HV0.2, about 1.45 times that of the Ni45 coating, and its wear resistance is 36.36 min/mg, about 60.6 times that of the Cr12MoV steel base material and about 23.76 times that of the Ni45 coating. [ABSTRACT FROM AUTHOR]

The effect of Si on the microstructure and properties of hypereutectic high-chromium cast iron was investigated. The results show that Si is only solid-dissolved in the matrix, and the content of Si is higher in the matrix near the edge of the primary carbide. As the Si content increased from 0.5 to 2.6%, the primary carbides in hypereutectic high-chromium cast iron were significantly refined, and the refining mechanism was verified by first-principles calculations. The increase of silicon content also leads to the increase of carbide volume fraction from 52.4 to 63.9%, the decrease of austenite volume fraction from 45.8 to 2.0%, and the matrix structure gradually transforms from γ-Fe to α-Fe. After hypereutectic high-chromium cast iron was quenched at 1050 °C, a large amount of secondary carbides were precipitated in the matrix and the precipitation of secondary carbides decreased significantly with the increase of silicon content. After quenching at 1050 °C, the hardness of hypereutectic high-chromium cast iron increased significantly, but the hardness of high-silicon (1.9Si and 2.6Si) samples did not change significantly. Increasing the quenching temperature and prolonging the holding time can significantly improve the hardness of high-silicon samples. The increase of silicon content can significantly improve the wear resistance of hypereutectic high-chromium cast iron. When the silicon content exceeds 1.9%, the wear resistance decreases. [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 ?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 oC, 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 oC and tempered from 200 oC has excellent combined properties; its hardness and impact toughness are 61.5 HRC and 8.8 J.m-2 respectively.

In order to solve the problems of low hardness and poor wear resistance of titanium alloy, laser cladding technology was used to prepare NiCrBSi coatings with different amounts of B4C on the surface of Ti-6Al-4V alloy. The effects of B4C content on the microstructure evolution, hardness, fracture toughness, and wear resistance of NiCrBSi coatings were investigated. The results showed that with an increase of B4C addition, the size and number of ceramic phases TiB2, TiC, and CrB in the coating increased, and the ceramic phases were dispersed in the coating. The average microhardness of the coating with 9 wt.% B4C addition was the highest, reaching 1250.3 HV0.2, which is 15% higher than that of the coating without B4C addition. After adding B4C, the fracture toughness of the coating increased. When the addition of B4C was 3 wt.%, the fracture toughness of the coating was the highest, reaching 1.42 MPa m1/2, which is 178.4% higher than that of the coating without B4C. With the increase of the addition of B4C, the wear loss of the coating decreased and the wear resistance increased. [ABSTRACT FROM AUTHOR]

The effects of different partitioning temperatures and time on the microstructure and properties of Mn-Si-Cr alloy steel were investigated. The results showed that with the increase in the partitioning temperature or the extension of the partitioning time, the martensite arrangement in the Mn-Si-Cr alloy steel became irregular, and the boundary was gradually blurred; the austenite mainly existed in the form of thin film, and the austenite content increased at first and then decreased gradually. When the partitioning temperature was too high or the partitioning time was too long, all led to the decomposition of austenite into low-carbon bainite and carbides. With the increase in the temperature, the hardness of the samples decreased gradually, the wear weight loss increased gradually, and the impact toughness increased linearly. With the extension of the partitioning time, the hardness of the sample gradually decreased. When the partitioning time is 5-10min, the hardness decreases greatly. When the partitioning temperature was 350 °C and the partitioning time was 60s, the test steel can have hardness, impact toughness, and wear resistance and has good comprehensive mechanical properties. [ABSTRACT FROM AUTHOR]

A dense Cu-10Sn alloy bulk specimen was obtained by optimizing the laser powder bed fusion (L-PBF) processing, and the relative density of the specimen reached 99.7%. The grain morphology was mainly the columnar dendrite and inter-dendritic phases generated along the solidification direction. Tensile testing and detailed microstructural characterization were carried out on specimens in the as-built and heat-treated condition. Under the quasi-static tensile condition, the yield strength (σ0.2), ultimate tensile strength (UTS), and the elongation of the as-built Cu-10Sn specimen were 392 MPa, 749 MPa and 29%, respectively. After the solution treatment at 800 °C for 4 h, and aging treatment at 400 °C for 2 hours, the microstructure of the specimen transformed from the columnar grain to equiaxed grain, the dislocation density decrease, and numerous annealing twins were observed in the heat-treated state. Therefore, the quasi-static tensile yield strength (σ0.2) of the specimen was reduced to 245 MPa. However, the UTS and the elongation were increased to 840 MPa and 56%, respectively, due to the interaction between annealing twins and equiaxed grain. [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]

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]

The effect of austenitizing temperatures at 850, 880, 910, 940, 970 and 1000 °C, respectively, and tempering at 250 °C on the microstructure, mechanical properties, strengthening and toughening mechanism, and wear behavior of Si-Mn-Mo cast steel containing 0.45%C-2.0%Si-1.0%Mn-0.3%Mo-0.8%Cr-0.004%B were systematically investigated. The results indicated that the microstructure of water quenching Si-Mn-Mo cast steel was mainly composed of lenticular martensite, martensite/austenite, bainitic ferrite and retained austenite. After tempering, the homogeneity of the microstructure improved. As the austenitizing temperature increased, the hardness of the steel increased first, and then it remained almost constant, the impact toughness decreased significantly, and the wear loss decreased first and then increased. Under low wear load, the steel austenitizing at 910 °C had excellent wear resistance before and after tempering. Under high wear load, after tempering, the steel austenitizing at 850 °C had the optimum wear resistance. The wear mechanisms were mainly abrasive wear, oxidation wear and adhesive wear. [ABSTRACT FROM AUTHOR]

The influence of the austempering process on microstructure evolution, mechanical properties, wear resistance, and corrosion resistance of Cu-bearing carbidic austempered ductile iron (CADI) was investigated. The results show that with an increase in the austempering temperature, the amount of acicular ferrite decreases, the volume fraction and carbon content of retained austenite increase gradually, the hardness and tensile strength decrease, and the impact toughness and corrosion resistance increase. Wear tests show that as the austempering temperature increases, the wear resistance of Cu-bearing CADI is improved and decreases when the temperature exceeds 300 °C. Comparing to the conventional single-step austempering process, two-step austempering process (namely added pre-quenching at 260 °C) significantly improves the wear resistance of Cu-bearing CADI by more than 16% without compromising toughness. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the effect of titanium modification on microstructures and properties of carbidic austempered ductile iron (CADI) containing 3.72 wt.% C, 2.77 wt.% Si, and 0.51 wt.% Mn. The results showed that with the addition of 0.1 wt.% Ti, TiC particles were formed, and distributed in carbides and matrix. Microstructural observation indicated that the maximum diameter of graphite nodules decreased from 58 to 40 μm, and the shape of carbides transformed from network to fragmentation, which was related to the nucleation of the eutectic structure (γ + (Fe, Cr)3C) where TiC particles act as the nucleus. After isothermal quenching at 300 °C, the hardness of Ti-bearing CADI was 3.5 HRC higher than ordinary CADI, and the impact toughness was increased by 14.3%. Additionally, due to the decrease in exfoliation, the wear loss of Ti-bearing CADI was 14.8% lower than ordinary CADI during the block-on-ring wear test at the surface load of 300 N. [ABSTRACT FROM AUTHOR]

In this study, particle and short fiber-reinforced titanium matrix composite coatings are prepared via laser in situ technique using (0.5 and 50 μm) TiB2 and Ti powder as cladding materials. The microstructure and properties of the composite coatings are studied, and the changing mechanism of the microstructure is discussed. The results reveal that particle agglomeration is prone to appear with using fine TiB2 particles. Decomposition of the particles preferentially occurs with using coarse TiB2 particles. The cracks and pores on the surface of the coating are formed at a lower laser energy density. With the increase in the laser energy density, cracking on the surface of the coating diminishes, but the coating exhibits depression behavior. The depression extent of the coating using fine TiB2 particle as the reinforcement is much less than that of the coating using coarse TiB2 particle. Moreover, the size of the aggregate and the tendency of cracking can be reduced with the increase in Ti addition. Meanwhile, short TiB fiber bundles are formed by the diffusion mechanism of rod aggregate, and randomly oriented TiB short fibers are formed mainly by the dissolution-precipitation mechanism of fine TiB2 particles. Moreover, the growth of short TiB fibers can be in an alternating manner between B27 and Bf structures. The micro-hardness and wear resistance of the coatings are evidently higher than that of the titanium alloy substrate. The wear resistance of the large size TiB2 coating is higher than that of the small size TiB2 coating under the condition of low load. [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]

This study investigates the effect of cerium on the microstructures, mechanical properties of medium carbon Fe-B cast alloy. The as-cast microstructure of Fe-B cast alloy consists of the eutectic boride, pearlite, and ferrite. Compared with the coarse eutectic borides in the unmodified alloy, the eutectic boride structures in the modified alloy are greatly refined. Cerium promotes the formation of CeO phase. CeO can act as effective heterogeneous nuclei of primary austenite, and refine austenite and boride. After heat treatment, the impact toughness of the modified alloy is higher than that of the unmodified alloy because there are more broken borides in the modified alloy. Meanwhile, the fracture mechanism of medium carbon Fe-B alloy is depicted and analyzed by using fractography. [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]

Pure Copper (Cu) is very difficult to prepare using selective laser melting (SLM) technology. This work successfully prepared the pure Cu with high relative density and high strength by the SLM technology using a surface oxidation treatment. The gas-atomized pure Cu powder was used as the feedstock in this work. Before the SLM process, the pure Cu powder was initially handled using the surface oxidation treatment to coat the powder with an extremely thin layer of Cu2O. The SLMed highly dense specimens contain α-Cu and nano-Cu2O phases. A relationship between the processing parameters (laser power (LP), scanning speed (SS), and hatch space (HS)) and density of Cu alloy in SLM was also investigated. The microstructure of SLMed Cu consists of fine grains with grain sizes ranging from 0.5 to ~30 μm. Tensile testing and detailed microstructural characterization were performed on specimens in the as-SLMed and pure copper state specimens. The mechanical property experiments showed that the specimens prepared by SLM technology containing nano-oxide phases had higher yield strength and tensile strength than that of other SLM-built pure copper. However, the elongation was remarkably decreased compared to other SLM-built pure copper, due to the fine grains and the nano-oxides. [ABSTRACT FROM AUTHOR]

This work investigated the microstructure and mechanical property of high-boron multi-component alloy with Fe, B, C, Cr, Mo, Al, Si, V, Mn and different contents of Ti. The results indicate that the as-cast metallurgical microstructure of high-boron multi-component alloys consist of ferrite, pearlite and borocarbide. In an un-modified alloy, continuous reticular structure of borocarbide is observed. After titanium addition, the structure of borocarbide changes into a fine and isolated morphology. TiC is the existence form of titanium in the alloy, which acts as the heterogeneous nuclei for eutectic borocarbide. Moreover, impact toughness of the alloy is remarkably improved by titanium modification. [ABSTRACT FROM AUTHOR]

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]

Abstract: The microstructure and crystallography of eutectic borides and secondary precipitations in 18wt.% Cr–4wt.% Ni–1wt.% Mo–3.5wt.% B–0.27wt.% C steel have been investigated extensively. The results show that the as-cast microstructure of Cr–Ni–Mo-containing Fe–B steel is composed of a dendritic martensite with large interdendritic eutectic borides. Transmission electron microscopy (TEM) results confirm that the borides are indexed to Cr- and Mo-rich M2B-type borides with the chemical formulas of Fe(1.35–1.36)Cr(0.92–1.05)B0.96 and Fe0.73Cr0.45Mo0.78B, respectively. The cluster-like boride possesses a possible orientation relationship between body-centred orthorhombic Cr-rich M2B and martensite with //〈110〉α growth direction. After destabilization, M23(C, B)6 secondary borocarbide with a specific orientation relationship precipitates first and thereafter coarsens following the appearance of M7(C, B)3 precipitation with the increasing destabilization temperature at the same soaking time, thus leading to a large decrease of Cr content in the martensite. However, no M6(C, B) secondary borocarbide is found in as-destabilized Fe–B steel. Destabilization treatment has no effect on the morphology of eutectic borides. The secondary borocarbides have the stoichiometry of (Fe18.26Cr4.74)(B, C)6 and (Fe3.86Cr3.14)(B, C)3 respectively. The high-resolution TEM results indicate that the nucleation and precipitation of M23(C, B)6 occur at the grain/subgrain boundaries as well as partial within martensite, and a subsequent transformation from M23(C, B)6 to M7(C, B)3 takes place in situ, which is probably owing to the crystalline defects of dislocations and stacking faults in the structures caused by lattice distortion. [Copyright &y& Elsevier]

Extreme High-Speed Laser Metal Deposition (EHLMD) is an efficient additive manufacturing technology that can quickly form difficult-to-machine materials. However, the rapid melting and solidification of EHLMD has the characteristic of forming a metastable microstructure. This study examines the effect of different aging temperatures on the microstructure and properties of EHLMD K648 superalloy. It is found that the formation of long needle-like α-Cr phase and γ' phase at lower aging temperatures (750 °C and 800 °C) is more beneficial for improving the strength of EHLMD K648 superalloy. The tensile strength was highest at 750 °C (1236 MPa) but its elongation was low (9.4 %). As the aging temperature increased (850–900 °C), the α-Cr phase transformed into rods and small particles, resulting in a decrease in tensile strength and an increase in elongation. At 900 °C, the tensile strength was 918 MPa and the elongation was 21.0 %. With further increase in aging temperature (>900 °C), coarse carbide and α-Cr phase precipitated in EHLMD K648 superalloy, causing its tensile strength and elongation to decrease. When the aging temperature reached 1000 °C, the tensile strength and elongation decreased to 790 MPa and 13.3 %, respectively. • The microstructure and mechanical properties of EHLMD K648 superalloy were investigated by different aging temperature. • The α-Cr phase evolves from long needle-like to rod-like and coarse particles with increase of aging temperature. • As the aging temperature increases, the tensile strength gradually decreases. [ABSTRACT FROM AUTHOR]

In present study, Fe-based composite layers were fabricated on steel substrate by laser cladding with or without the addition of Nb and B 4 C in Fe-based alloy powders. The phase composition, microstructure evolution, microhardness and wear properties of Fe-based composite layers were studied. The results showed that the phases in the Fe-based composite layer were mainly α-Fe, Fe 2 B, Cr 7 C 3 and Cr 23 C 6. The addition of Nb and B 4 C resulted in the in-situ formation of NbC phase, an increase in the amount of Fe 2 B phase, and the refinement of the microstructure in the Fe-based composite layer. The microhardness of the Fe-based composite layer was increased by 269.5 HV 0.5 and the wear resistance was improved to about 1.5 times the original wear resistance when the 5% Nb and 5% B 4 C powders were added. The wear mechanisms of both two Fe-based composite layers were abrasive wear and adhesive wear. • A new Fe-based composite layers were fabricated by laser cladding. • In-situ NbC phase was generated. • The microstructure evolution mechanism were proposed. • The microhardness and the wear resistance was improved by adding Nb and B 4 C. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing (WAAM) technology was adopted to deposite 2Cr13 thin-wall part using robotic cold metal transfer (CMT) equipment; the process stability, phase identification, microstructural evolution, and tensile properties in different layers were investigated. The results showed that a smooth surface was obtained for each layer due to the stable droplet transfer process, which ensured a stable deposition process. Positions in different layers had no significant influence on the structural aspects of the as-fabricated part according to XRD results. Elongated ferrite grains and fine-grained acicular martensite within the matrix in the top layer were recrystallized, instead of a spatial periodicity of martensite laths within equiaxed ferrite grains in the inner layers. Martensite content was increased gradually away from the base metal in the 05–25 th layers except nearly 100% martensite in the first layer. Long axis of martensite laths was randomly distributed in the X-Y plane in the both top and middle regions, while an epitaxial growth parallel to the building direction was found in the X-Z and Y-Z planes. Higher homogeneous ultimate tensile strength (UTS) and strong anisotropy in poorer ductility were obtained for the AM part when compared with the as-solutioned counterpart. Fracture behavior was transformed from ductile to mixed-mode, and finally to brittle from the 01 st layer to the 25 th layer. [ABSTRACT FROM AUTHOR]