Automatic remelting and enhanced mechanical performance of a plasma sprayed NiCrBSi coating

Thermal sprayed NiCrBSi coatings often have some shortcomings such as poor cohesion and adhesion, which degrade their properties and are expected to be eliminated by the remelting process. However, there is still a lack of remelting methods combining the advantages of reliability, reproducibility and low-cost. This work developed a remelting method to remelt the as-sprayed NiCrBSi by plasma gun in an automatic mode using optimized parameters. The remelting process reduces the porosity, eliminates the lamellar boundaries and promotes the formation of metallurgical bonding at the coating/substrate interface. Therefore, the hardness (803 HV0.5) and bonding strength (165 MPa) of the remelted NiCrBSi coating are about 22% and 516% higher than the corresponding ones of the as-sprayed NiCrBSi counterpart (hardness: 657 HV0.5; bonding strength: 32 MPa). The remelted NiCrBSi coating also exhibit significantly enhanced wear resistance compared with the substrate and as-sprayed one. Comparison between the remelted NiCrBSi coatings prepared by various remelting methods indicates that the remelting process used in this work is prominently useful for wider industrial applications since it is reliable, reproducible and convenient. •Automatic remelting was conducted on a sprayed NiCrBSi coating by a plasma torch.•Porosity is significantly reduced from 2.7% to 0.8% in the remelted NiCrBSi coating.•A metallurgical bonding interface of coating/substrate forms after remelting process.•Hardness, bonding strength and wear performance are improved after remelting process.