Microstructural Evolution and Mechanical Evaluation of a Laser-Induced Composite Coating on a Ni-Based Superalloy...

A Ni-17Mo-7Cr-based superalloy was laser surface-modified to improve its tribological properties. Si particles were employed as coating materials. Si melted on the surface of the alloy during the process, triggering the formation of Mo₆Ni₆C carbides and Ni-Si intermetallics. A defect-free coating obtained was mostly made up of primary Mo₆Ni₆C and γ-Ni₃₁Si₁₂, as well as a eutectic structure of β₁-Ni₃Si and α-Ni-based solid solution (α-Ni (s.s)). The volume fraction of hard reinforcements (Mo₆Ni₆C, γ-Ni₃₁Si₁₂, and β₁-Ni₃Si) reached up to 85% in the coating. High-temperature microstructural stability of the coating was investigated by aging the coating at 1073 K for 240-480 h, to reveal its microstructural evolution. In addition, the mechanical performance of the coating was investigated. The nanoscale elastic modulus and hardness of Mo₆Ni₆C, γ-Ni₃₁Si₁₂, and α-Ni (s.s) were characterized using the nanoindentation tests. The nanoscratch tests were performed to measure the local wear resistance of the coating. Lastly, the Vickers hardness distribution across the cross-section of the coating before and after thermal exposure was compared. The work performed provides basic information understanding the microstructural evolution and mechanical performance of laser-induced coatings on Ni-based superalloys.