Microstructure and tribological properties of nickel-based coatings by plasma enhanced high-speed arc spraying: Non-transfer arc, transfer arc modes

Mechanical equipment in long-term service in the marine environment is subject to friction and wear due to movement, and the preparation of coatings on the surface of mechanical components using thermal spraying is one of the ways to solve this problem. In this work, Ni-based coatings were prepared using both transferred and non-transferred arc modes of the team's self-developed plasma-enhanced high-speed arc spraying (PE-HAS) technique. The microstructure, mechanical properties, and tribological properties were mainly investigated. The results show that the Ni-based Inconel 625 wire coating (S1 coating) has good surface cross-section morphology and lower porosity compared with the Inconel 625 powder coating (S2 coating). EBSD results show that the S1 coatings are mainly equiaxed and fine crystals, while the S2 coating is mainly fine crystals. The TEM results show that the main phase in the S1 coating is the gamma- Ni phase with a face-centered cubic (FCC) structure, while the S2 coating is mainly the Cr1Ni3 phase. The results of the mechanical property study show that the S1 coating has better performance than the S2 coating, with microhardness and bond strength values of 436.43 HV 0.2 and 60.7 MPa for the S1 coating and 238.67 HV 0.2 and 49.7 MPa for the S2 coating, respectively. The friction coefficients of S1 and S2 coatings are 0.60 and 0.76, respectively. Consequently, S1 coatings have better wear resistance, and the main wear mechanisms are abrasive wear, adhesive wear, and oxidative wear. The good performance of the S1 coating was attributed to the plasma-enhanced high-speed arc spraying using a dual-anode structure in the transfer arc mode, which resulted in adequate heating of the filaments, higher energy of the transfer arc, and higher melt droplet flight speed and temperature.