Effect of powders recycling on microstructure evolution and wear mechanism of plasma sprayed Ni625-WC composite coating

The utilization rate of metal powders during the preparation of plasma-sprayed coatings is typically below 70 %, which has raised significant concerns regarding efficiency. The microstructure evolution and wear mechanism of plasma-sprayed Ni625-WC composite coatings with received powders (C-p1) and recovered powders (C-p2) were studied to investigate the feasibility of powder recycling. The results showed that the boundary layer at WC particles in C-p2 was 2.84 μm thicker than that in C-p1. Decarburized WC products were dispersed nucleation to form block M23C6 at the boundary of WC particles and within Inconel 625 matrix in C-p1. In contrast, the larger contact area of block M23C6 after initial heating promoted the nucleation and growth of acicular M23C6 in C-p2. In addition, the wear rate of C-p2 is 9.1 % lower than that of C-p1. Although the higher elastic modulus (E) of C-p1 caused the Inconel 625 matrix to adhere more strongly to WC particles, resulting in higher degree adhesive wear rather than exfoliations and less adhesion in C-p2, the presence of harder and more uniformly distributed acicular M23C6, and higher microhardness (H)/E ratio in C-p2, improved the wear resistance. Structure evolution mechanism of WC particles and the boundary of WC particles: (a) the composite coating with received powder, (b) the composite coating with recovered powder. Diagram of the wear mechanism: (a) the composite coating with received powder, (b) the composite coating with recovered powder. [Display omitted] •Composite coatings used by received and recovered powers were prepared.•Boundary layer of different thicknesses was observed in both coatings.•Block and acicular M23C6 were observed in C-p1 and C-p2, respectively.•C-p2 shows higher wear resistance and powder recycling is feasible.