1 Research status of metal coatings Thermal spray metal coatings are research and application of earlier wear-resistant coatings, commonly used metal (Mo, Ni), carbon steel and low alloy steel, stainless steel and Ni-Cr alloy series coating . Flame spray, arc spray, plasma spray, HVOF and explosion spray processes are generally used. The coating has the advantages of high bonding strength with the substrate, good wear resistance and corrosion resistance, etc., and is used for repairing worn parts and machining super bad parts. .
When aluminum alloy plasma spraying technology is used to spray parts such as piston rings, synchronizer rings, and cylinders, the coating has good wear resistance, high bonding strength, and excellent resistance to adhesive wear, and it has good properties under the conditions of lubricating oil. Anti-seize and tensile properties. High-carbon steel wire, stainless steel (Crl3 type, 18-8 type, etc.) alloy wire is a commonly used wear-resistant corrosion-resistant spray material. With high strength, good wear resistance, wide source, low price and so on. NiCr coating has good heat resistance, corrosion resistance and erosion wear resistance, and can be used as a protective coating for superheater tubes and reheater tubes of power station boilers. Flame and plasma spraying methods can be used to produce different microstructures. The NiCr metal wear resistant coating has higher porosity and oxide content in the coating.
2 Research status of ceramic coatings Thermal spray ceramic powders include oxides, carbides, borides, nitrides, and silicides. They are crystalline or non-crystalline compounds consisting of metallic and non-metallic elements. The ceramic coating has high melting point, high hardness and good wear resistance, corrosion resistance and high temperature stability. However, the sprayed ceramic coating process is complicated, the cost is high, and the surface of the coating is prone to cracks, and the thermal fatigue resistance is inferior to the metal coating. Moreover, the toughness of the coating is poor and cannot be used to withstand large impact loads. At present, the commonly used ceramic coatings are A12O3, TiO2, Cr2O3, ZrO2, WC, TiC, Cr3C2, TiB2, etc. and are generally prepared by plasma spraying, flame spraying, HVOF and explosion spraying techniques.
Ren Jingri et al studied the sliding friction wear properties of plasma sprayed A12O3-40%TiO2 and Cr2O3 ceramic powder coatings, and pointed out that the wear resistance of Cr2O3 coating is higher than that of A12O3-40%TiO2 coating, and the wear mechanism of Cr2O3 coating is mainly For abrasive wear, the Cr2O3 coating exhibits brittle fracture characteristics under large loads. The wear mechanism of A12O3-40% TiO2 coating mainly manifests as plastic deformation and layered peeling. Chen Chuanzhong et al. studied the A12O3 plus TiO2 plus NiCrAlY composite ceramic coating, because the molten TiO2 and A12O3 formed a certain degree of mutual solubility, can reduce the porosity of the coating, and further improve the strength, toughness and wear resistance of the coating.
Lin et al. studied the sliding friction wear properties of plasma sprayed multilayer metal and ceramic coatings. The spray sequence was as follows: First, spray NiCr on the substrate and then use different ratios of NiCr-Cr2O3 transition layer with 100% Cr2O3 on the surface. It has been found that a suitable transition layer of metal and ceramic can improve the wear resistance of the coating. The main wear mechanisms of the coatings are brittle fracture, abrasive wear, adhesion and oxidative wear.
3 Research status of metal ceramic coatings Metal and ceramic materials have their own unique superior performance and obvious performance weaknesses. How to combine the superior performance of metal and ceramic materials has always been the research direction of materials science and engineering. The metal-ceramic composite coating technology, that is, the ceramic phase with proper particle shape and size is evenly distributed on the plastic matrix, and the superior combination of metal and ceramic is successfully achieved, and the strength and toughness of the existing metal are prepared, and the ceramic is resistant to high temperatures. The composite materials with advantages of wear resistance, corrosion resistance and the like have greatly broadened the respective application ranges of metal materials and ceramic materials, and have been successfully applied in the aviation, aerospace, chemical, mechanical, and electric power industries. The most widely used metal ceramic coatings in industry are: Cr3C2-NiCr, WC-Co. Most use HVOF, plasma and explosive spray process.
The Cr3C2-NiCr cermet coating consists of a hard chromium carbide hard phase and a ductile nickel-chromium alloy phase. It has a high temperature hardness, excellent high temperature wear resistance, corrosion resistance, oxidation resistance and a high Bonding strength, widely used in high temperature (530 ~ 9000 °C) abrasive wear, corrosion wear and erosion wear conditions working parts, such as continuous annealing line furnace roller, rolling mill continuous production line core roller, cylinder piston ring Cylinder lining and so on. The TiB2-based cermet coating has high melting point, high hardness, good electrical and magnetic properties, and high corrosion resistance, and is a potential alternative to Cr3C2 for high-temperature, wear-resistant cermets. Better wear resistance than A12O3, Cr3C2-NiCr, WC-Co.
WC-based cermet coatings are commonly used in abrasive wear and erosion wear conditions below 450°C. Xu Xiangyang studied the fretting wear mechanism of plasma sprayed WC/18Co coating. The results show that the initial fretting wear of the coating is dominated by adhesive wear, the coating has high hardness, strong anti-adhesion ability and slight abrasion; the stable phase is dominated by fatigue delamination and brittle cracking, and the coating has large brittleness. The combination of low strength, easy to wear. Oxide inclusions in the spray coating are the major cause of the inability of the coating to resist fretting wear.
4 Research Status of Amorphous Coatings Amorphous is a long-range disordered, short-range and orderly material. The physical and chemical properties of amorphous materials are often superior to those of the corresponding crystalline materials. They have high strength, high toughness, high hardness, high corrosion resistance, and soft magnetic properties. They are a promising new type of metal materials. . Thermal spraying of amorphous alloy coatings is a new area that has been extensively studied in materials science in recent years. Thermal spraying technology has begun to attract widespread attention as one of the preparation methods for large-area amorphous coatings. Plasma spraying, HVOF, and Explosion spray.
To Xinghua et al., the plasma spraying process was used to prepare Fe-based amorphous alloy coatings (including Si, B, Cr, Ni, etc.). The microstructure of the coating was uniform in all areas. The coating had high density, low porosity, and oxide content. Less, and with a high hardness, microhardness in the range of 530 ~ 790HV0.1, the coating and the substrate combined well.
Jin et al. studied the microstructure and wear resistance of explosively sprayed Fe-Cr-B alloy coatings. The results show that the coating has good anti-wear and anti-corrosion properties, and the coating produces an amorphous surface film dynamically during the sliding wear process, so that the wear resistance of the coating is significantly improved and the friction coefficient is significantly reduced.
In summary, the use of HVOF, plasma spray, arc spray, explosion spray and other methods of spraying metal, ceramic, cermet and amorphous wear-resistant coating, can effectively improve the wear resistance of the matrix material. In-depth study of the wear mechanism of the thermal spray coating and the influence of the coating structure on the wear characteristics provide a theoretical basis for improving the coating organization, optimizing the spraying process, and developing new wear-resistant coatings.
When aluminum alloy plasma spraying technology is used to spray parts such as piston rings, synchronizer rings, and cylinders, the coating has good wear resistance, high bonding strength, and excellent resistance to adhesive wear, and it has good properties under the conditions of lubricating oil. Anti-seize and tensile properties. High-carbon steel wire, stainless steel (Crl3 type, 18-8 type, etc.) alloy wire is a commonly used wear-resistant corrosion-resistant spray material. With high strength, good wear resistance, wide source, low price and so on. NiCr coating has good heat resistance, corrosion resistance and erosion wear resistance, and can be used as a protective coating for superheater tubes and reheater tubes of power station boilers. Flame and plasma spraying methods can be used to produce different microstructures. The NiCr metal wear resistant coating has higher porosity and oxide content in the coating.
2 Research status of ceramic coatings Thermal spray ceramic powders include oxides, carbides, borides, nitrides, and silicides. They are crystalline or non-crystalline compounds consisting of metallic and non-metallic elements. The ceramic coating has high melting point, high hardness and good wear resistance, corrosion resistance and high temperature stability. However, the sprayed ceramic coating process is complicated, the cost is high, and the surface of the coating is prone to cracks, and the thermal fatigue resistance is inferior to the metal coating. Moreover, the toughness of the coating is poor and cannot be used to withstand large impact loads. At present, the commonly used ceramic coatings are A12O3, TiO2, Cr2O3, ZrO2, WC, TiC, Cr3C2, TiB2, etc. and are generally prepared by plasma spraying, flame spraying, HVOF and explosion spraying techniques.
Ren Jingri et al studied the sliding friction wear properties of plasma sprayed A12O3-40%TiO2 and Cr2O3 ceramic powder coatings, and pointed out that the wear resistance of Cr2O3 coating is higher than that of A12O3-40%TiO2 coating, and the wear mechanism of Cr2O3 coating is mainly For abrasive wear, the Cr2O3 coating exhibits brittle fracture characteristics under large loads. The wear mechanism of A12O3-40% TiO2 coating mainly manifests as plastic deformation and layered peeling. Chen Chuanzhong et al. studied the A12O3 plus TiO2 plus NiCrAlY composite ceramic coating, because the molten TiO2 and A12O3 formed a certain degree of mutual solubility, can reduce the porosity of the coating, and further improve the strength, toughness and wear resistance of the coating.
Lin et al. studied the sliding friction wear properties of plasma sprayed multilayer metal and ceramic coatings. The spray sequence was as follows: First, spray NiCr on the substrate and then use different ratios of NiCr-Cr2O3 transition layer with 100% Cr2O3 on the surface. It has been found that a suitable transition layer of metal and ceramic can improve the wear resistance of the coating. The main wear mechanisms of the coatings are brittle fracture, abrasive wear, adhesion and oxidative wear.
3 Research status of metal ceramic coatings Metal and ceramic materials have their own unique superior performance and obvious performance weaknesses. How to combine the superior performance of metal and ceramic materials has always been the research direction of materials science and engineering. The metal-ceramic composite coating technology, that is, the ceramic phase with proper particle shape and size is evenly distributed on the plastic matrix, and the superior combination of metal and ceramic is successfully achieved, and the strength and toughness of the existing metal are prepared, and the ceramic is resistant to high temperatures. The composite materials with advantages of wear resistance, corrosion resistance and the like have greatly broadened the respective application ranges of metal materials and ceramic materials, and have been successfully applied in the aviation, aerospace, chemical, mechanical, and electric power industries. The most widely used metal ceramic coatings in industry are: Cr3C2-NiCr, WC-Co. Most use HVOF, plasma and explosive spray process.
The Cr3C2-NiCr cermet coating consists of a hard chromium carbide hard phase and a ductile nickel-chromium alloy phase. It has a high temperature hardness, excellent high temperature wear resistance, corrosion resistance, oxidation resistance and a high Bonding strength, widely used in high temperature (530 ~ 9000 °C) abrasive wear, corrosion wear and erosion wear conditions working parts, such as continuous annealing line furnace roller, rolling mill continuous production line core roller, cylinder piston ring Cylinder lining and so on. The TiB2-based cermet coating has high melting point, high hardness, good electrical and magnetic properties, and high corrosion resistance, and is a potential alternative to Cr3C2 for high-temperature, wear-resistant cermets. Better wear resistance than A12O3, Cr3C2-NiCr, WC-Co.
WC-based cermet coatings are commonly used in abrasive wear and erosion wear conditions below 450°C. Xu Xiangyang studied the fretting wear mechanism of plasma sprayed WC/18Co coating. The results show that the initial fretting wear of the coating is dominated by adhesive wear, the coating has high hardness, strong anti-adhesion ability and slight abrasion; the stable phase is dominated by fatigue delamination and brittle cracking, and the coating has large brittleness. The combination of low strength, easy to wear. Oxide inclusions in the spray coating are the major cause of the inability of the coating to resist fretting wear.
4 Research Status of Amorphous Coatings Amorphous is a long-range disordered, short-range and orderly material. The physical and chemical properties of amorphous materials are often superior to those of the corresponding crystalline materials. They have high strength, high toughness, high hardness, high corrosion resistance, and soft magnetic properties. They are a promising new type of metal materials. . Thermal spraying of amorphous alloy coatings is a new area that has been extensively studied in materials science in recent years. Thermal spraying technology has begun to attract widespread attention as one of the preparation methods for large-area amorphous coatings. Plasma spraying, HVOF, and Explosion spray.
To Xinghua et al., the plasma spraying process was used to prepare Fe-based amorphous alloy coatings (including Si, B, Cr, Ni, etc.). The microstructure of the coating was uniform in all areas. The coating had high density, low porosity, and oxide content. Less, and with a high hardness, microhardness in the range of 530 ~ 790HV0.1, the coating and the substrate combined well.
Jin et al. studied the microstructure and wear resistance of explosively sprayed Fe-Cr-B alloy coatings. The results show that the coating has good anti-wear and anti-corrosion properties, and the coating produces an amorphous surface film dynamically during the sliding wear process, so that the wear resistance of the coating is significantly improved and the friction coefficient is significantly reduced.
In summary, the use of HVOF, plasma spray, arc spray, explosion spray and other methods of spraying metal, ceramic, cermet and amorphous wear-resistant coating, can effectively improve the wear resistance of the matrix material. In-depth study of the wear mechanism of the thermal spray coating and the influence of the coating structure on the wear characteristics provide a theoretical basis for improving the coating organization, optimizing the spraying process, and developing new wear-resistant coatings.
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