Investigation on Tribological Properties of Stellite3/Ti₃SiC₂ Composite Coatings on Inconel 718 Alloy by Laser Cladding

Inconel 718 is a nickel-based superalloy which is widely used in various industrial field to manufacture industrial parts, such as aviation on the engine, sheet metal welding parts and so on. Because of the long-term service in harsh working conditions such as high temperature and high pressure, alloy structural parts often fail due to wear, fatigue and other reasons, resulting in the reduced service life. The production cost will increase if it is directly scrapped, so it is of great significance to improve the tribological properties of Inconel 718 alloy at high temperature. Therefore, three kind of composite coatings, Stellite3−5%Ti₃SiC₂ (C1), Stellite3-10%Ti₃SiC₂ (C2) and Stellite3-15%Ti₃SiC₂ (C3) (mass fraction) were prepared on the surface by laser cladding. The tribological behavior at room temperature and 600 ℃ was investigated by phase analysis, microstructure and microhardness analysis. The phase analysis results showed that the coating mainly contains γ-Co, (Fe, Ni) solid solution, intermetallic compound Cr₂Ni₃ and carbides WC_x, TiC and Cr₇C₃. And due to the existence of these hard phase carbides, the microhardness of the coating increased to 1.6~2.5 times than that of the matrix (262.7 HV_0.5), which were 662.74 HV_0.5, 521.47 HV_0.5 and 419.44 HV_0.5, respectively. The tribological properties of the three coatings had also been improved, and C1 coating had the best property at room temperature among them, for its friction coefficient was reduced by 20.52% and its wear resistance was increased by 85.45%; the wear resistance of C2 coating at 600 ℃ increased by 79.53%. At room temperature, the wear mechanisms of the substrate, C1 and C2 coatings were mainly plastic deformation and abrasive wear, while the C3 coating appeared adhesive wear because of the decrease of hardness. All samples were oxidized at 600 ℃, and the substrate showed severe plastic deformation and adhesive wear. The wear of the three coatings was reduced due to the addition of Ti₃SiC₂, which were mainly oxidative wear and abrasive wear.