Ni-based alloy/submicron WS 2 self-lubricating composite coating synthesized by Nd:YAG laser cladding

Abstract

Ni-based alloy matrix submicron WS 2 self-lubricant composite coatings were synthesized by Nd:YAG laser cladding in the present study. A novel high-energy ball milling method was adopted to encapsulate nano-Ni onto submicron WS 2 with an aim to prevent the mass loss of WS 2 during laser cladding process. Microstructure and phases of the laser-clad coatings were investigated to understand laser-cladding behaviors of two kinds of coating materials, i.e., Ni45–WS 2–CaF 2 and Ni60–WS 2 (nano-Ni-encapsulated). The bare submicron WS 2 and micron CaF 2 were hardly to compose into Ni45 matrix coatings even if increasing the weight percentage of both WS 2 and CaF 2 from 7.5 to 17.5%. Ni-based alloy matrix submicron WS 2 self-lubricant composite coatings were successfully synthesized through laser cladding of the Ni60–WS 2 (nano-Ni-encapsulated) coating, since the high-energy ball milling of nano-Ni onto submicron WS 2 significantly prevented the oxidization, reaction and vaporization of WS 2 and improved the interfacial compatibility between WS 2 and Ni60 matrix. The friction coefficient of the laser-clad Ni60–WS 2 (nano-Ni-encapsulated) coating was reduced to about 0.36 in comparison with that of the laser-clad Ni45–WS 2–CaF 2 and Ni60 coatings (about 0.5–0.6) as well as the wear resistance of the laser-clad Ni60–WS 2 (nano-Ni-encapsulated) was three times higher than that of the laser-clad Ni60 coating, respectively.