Microstructure and High-Temperature Tribological Properties of Nickel-Based Composite Coatings with Laser In Situ Induced TiC and MoSi2 Reinforcement

In order to improve the tribological properties of Inconel 718 alloy at elevated temperature, nickel-based composite coatings with in situ TiC and MoSi2 reinforcement were deposited onto Inconel 718 alloy via laser cladding the complex Hastelloy C276 alloy and Ti3SiC2 powder in this study. The influences of the in situ TiC and MoSi2 reinforcement from the complete decomposition of Ti3SiC2 powders on the microstructure, mechanical and tribological properties of prepared coatings were systematically investigated. These coatings exhibited a microstructure consisting of coarse gamma-Ni dendrites, slender interdendritic MoSi2 phases, and TiC ellipsoidal particles. The inclusion of an appropriate amount of in situ fine TiC and MoSi2 precipitates significantly inhibited the directional growth and coarsening of gamma-Ni dendrites, resulting in improved mechanical properties and wear resistance. Among the three types of coatings applied through laser cladding, the Ni-based composite coating with 20 wt.% Ti3SiC2 addition demonstrated relatively high hardness (538.4 HV0.3) and flexural strength (1651.37 MPa), coupled with a lower mean friction coefficient (0.39) and wear rate (3.16 x 10(-5) mm(3)/N m) at 30 degrees C. These TiC and MoSi2 reinforcements proved effective in reducing cutting stress and resisting plastic deformation, thereby enhancing friction coefficients and wear rates across the temperature range from 30 to 400 degrees C. The prepared coatings also exhibited promising wear resistance at 800 degrees C, attributed to the formation of protective tribofilm oxidative layers. However, the breakage of the lubricating tribofilms caused obvious wear damage and exacerbated friction coefficients and wear rates at 1000 degrees C.