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Laser cladding nickel-base coatings are playing an important role in improving the surface properties of materials due to their high bonding strength and good wear resistance.However，the hardness and wear resistance of common nickel-based coatings are difficult to meet the application requirements of parts in harsh environment due to the lack of wear-resistant hard phase.In order to further improve the wear resistance of the coating，several strategies were proposed by domestic and foreign scholars: mechanically adding or in-situ synthesizing hard ceramic particles in the coating，or adding graphene，carbon nanotubes and rare earth oxides in the coating，or establishing a prediction model between the process parameters and the coating performance and then optimizing the process parameters using algorithms such as adaptive chaos differential evolution algorithm and gray correlation analysis，or using auxiliary processing in laser cladding.In this paper，the influence of coating composition，process parameters and auxiliary treatment on wear resistance of nickel-base composite coating was reviewed，and the development prospect of laser cladding nickel-base composite coating was put forward.

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]

Nickel-based coatings obtained by laser melting are broadly applied for surface modification owing to their high bond strength and exceptional wear resistance. Nickel-based laser cladding coatings are also extensively employed in high temperature wear environments. In this paper, the research progress on improving the high temperature wear resistance of laser cladding nickel-based composite coatings was reviewed by introducing a hard ceramic phase, adding solid lubricants and rare earth elements. On this basis, the material system to enhance the high temperature wear resistance of coating was summarized from the perspectives of the type, addition amount, morphology and distribution law of the hard ceramic phase, etc. The synergistic effect of various lubricants on improving the high temperature wear resistance of coating was discussed, and the action mechanism of solid lubricants in the high temperature extreme environment was analyzed. Finally, this paper summarizes the main difficulties involved in increasing the high temperature wear resistance of nickel-based coatings and some problems worthy of attention in the future development. [ABSTRACT FROM AUTHOR]

This review examines the methods used to optimize the process parameters of laser cladding, including traditional optimization algorithms such as single-factor, regression analysis, response surface, and Taguchi, as well as intelligent system optimization algorithms such as neural network models, genetic algorithms, support vector machines, the new non-dominance ranking genetic algorithm II, and particle swarm algorithms. The advantages and disadvantages of various laser cladding process optimization methods are analyzed and summarized. Finally, the development trend of optimization methods in the field of laser cladding is summarized and predicted. It is believed that the result would serve as a foundation for future studies on the preparation of high-quality laser cladding coatings. [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]

• 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]

In this paper, the enhancement of NiCrBSi coatings by adding Cr3C2 were investigated. The NiCrBSi coatings with different additions of Cr3C2 were produced by laser cladding. The microstructure, hardness and wear resistance of the coatings were studied by optical microscope (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), microhardness tester and M-200 wear tester. It is found that the main phases in the coatings are γ -Ni, Cr 2 3 C6 and Cr7C3, and they also contain a small amount of CrB, Ni4B3 and Ni3Si2. Moreover, with the increase of Cr3C2 addition, the microhardness and wear resistance of coatings are obviously improved. When the addition of Cr3C2 is 20%, the wear resistance of the coating is the best, and the wear resistance of the coating increased by 191.2% than that of the Cr3C2-free coating. The wear resistance of coating decreases when the addition of Cr3C2 reaches 30%. [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 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]

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]

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]

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]

Agglomerated TiB particle and network-like structure-reinforced titanium matrix composite coatings were prepared by laser cladding of the Ni + TiB + Ti preplaced powders on Ti-6Al-4V alloy. The network-like structure mainly consisted of NiTi and NiTi. Through the experiment, it was found that the size of agglomerated particle gradually decreased with the increase of Ti content, but the number of the network-like structure first increased and then disappeared. In-situ reaction competition mechanism and the formation of network-like structure were discussed. The average micro-hardness gradually decreased with the increase of Ti content, but the average fracture toughness gradually increased. Meanwhile, the wear resistance of the coatings is higher than that of the substrate, but the wear loss of the coatings is gradually increased with the increase of Ti content. [ABSTRACT FROM AUTHOR]

The dilution rate has a significant impact on the composition and microstructure of the coatings, and the dilution rate and process parameters have a complex coupling relationship. In this study, three process parameters, namely laser power, powder feeding rate, and scanning speed, were selected as variables to design the orthogonal experiment. The dilution rate and hardness data were obtained from AlCoCrFeNi coatings based on orthogonal experiments. Then, a BP neural network was used to establish a prediction model of the process parameters on the dilution rate. The established BP neural network exhibited good prediction of the dilution rate of AlCoCrFeNi coatings, and the average relative error between the predicted value and the experimental value was only 5.89%. Subsequently, the AlCoCrFeNi coating was fabricated with the optimal process parameters. The results show that the coating was well-formed without defects, such as cracks and pores. The microhardness of the AlCoCrFeNi coating prepared with the optimal process parameters was 521.6 HV0.3. The elements were uniformly distributed in the microstructure, and the grain size was about 20–60 μm. The microstructure of the AlCoCrFeNi coating was only composed of the BCC phase without the existence of the FCC phase and intermetallic compounds. [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]

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]

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]

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]

Highlights • TiB fiber bundle with high aspect ratio can be formed in the cladding layer prepared with 0.5 μm TiB 2 particles. • High laser power is required to achieve TiB fiber bundle with high aspect ratio. • Agglomeration of 0.5 μm TiB 2 particles occurred during the solidification of the laser molten pool. • Crack propagation in the fiber bundles take place in a variety of ways. Abstract In this study, coatings are fabricated with laser cladding technique on titanium alloy substrate using TiB 2 powder (0.5 μm, 5 μm and 50 μm) as the cladding materials. The effects of different TiB 2 particle sizes and different laser powers on the microstructure of laser cladding layer are investigated. The results reveal that the cladding layer of high aspect ratio TiB fiber bundle is formed when using 0.5 μm TiB 2 as the cladding material under the condition of high laser power (2.5 kW) of TiB fiber bundle are formed when using 5 μm and 50 μm TiB 2 as the cladding materials under the condition of different laser powers. Combined with the evolution of microstructure in the cladding layers, the formation mechanism of high aspect ratio TiB fiber bundle is discussed. Meanwhile, the cladding layer of high aspect ratio TiB fiber bundle exhibits the advantages of high hardness and high wear resistance, and the predominant wear mechanisms of TiB fiber bundle are cutting and fracture. [ABSTRACT FROM AUTHOR]

TiB 2 particle and TiB short fiber reinforced titanium matrix composite coatings were prepared utilizing in situ synthesized technique by laser cladding on the surface of Ti6Al4V alloy. Through the experiment, it was found that the surface of the single-track coatings appeared in the depression, but it can be improved by laser track overlapping. With the increase of laser power density, the amount of TiB short fiber was increased, and the distribution of TiB 2 and TiB became more uniform from the top to bottom. The micro-hardness of TiB 2 /TiB coating showed a gradient decreasing trend, and the average micro-hardness of the coatings was two-fold higher than that of the substrate. Due to the strengthening effect of TiB 2 particle and TiB short fiber, the wear volume loss of the center of the coating was approximately 30% less than that of the Ti–6Al–4V substrate, and the wear mechanism of the coating was mild fatigue particle detachment. [ABSTRACT FROM AUTHOR]

TiB 2 /TiB gradient coating has been fabricated by a laser cladding technique on the surface of a Ti–6Al–4V substrate using TiB 2 powder as the cladding material. The microstructure and mechanical properties of the gradient coating were analyzed by SEM, EPMA, XRD, TEM and an instrument to measure hardness. With the increasing distance from the coating surface, the content of TiB 2 particles gradually decreased, but the content of TiB short fibers gradually increased. Meanwhile, the micro-hardness and the elastic modulus of the TiB 2 /TiB coating showed a gradient decreasing trend, but the fracture toughness showed a gradient increasing trend. The fracture toughness of the TiB 2 /TiB coating between the center and the bottom was improved, primarily due to the debonding of TiB 2 particles and the high fracture of TiB short fibers, and the fracture position of TiB short fiber can be moved to an adjacent position. However, the debonding of TiB 2 particles was difficult to achieve at the surface of the TiB 2 /TiB coating. [ABSTRACT FROM AUTHOR]