The role of the Counterbody Material on Tribological Properties of 316L+WC Composite Coatings processed by Laser Cladding

This work considers a metal matrix composite composed of 316L stainless steel and reinforcements of tungsten carbides (WC) particles (20 in vol.%), fabricated by laser cladding with a complex hierarchical microstructure (Figure) [T. Maurizi Enrici et al., Adv. Eng. Mater. (2020)].
Pin-on-disk tests were performed in order to determine the influence of the reinforcements on its wear behaviour. Particular attention was given to the counterbody, since the ball material has an important role in the wear behaviour. For this purpose, alumina and WC balls were chosen due to their high hardness.

By using alumina, a complex wear sequence was evaluated by looking at the variation of the friction coefficient (µ) and the penetration depth (PDe). The sequence involves different wear mechanisms. The use of alumina allows to determine easily the nature of the debris formed during the test since Al is not present in the composition of the composite. Nevertheless, this hard debris can lead to significant wear of the ball and a not realistic evaluation of the wear performance.
In contrast, the use of WC ball allows to obtain a good estimation of the wear resistance since the wear of the ball is negligible. Nevertheless, the use of WC ball leads to more difficulties in the interpretation of the wear mechanisms, since W is present in both counterbody and composite.

For both counterbodies, the novel approach of the interrupted test was applied, where wear tests are performed under the same conditions and strategically stopped at times corresponding to specific variations of μ and PDe. Post-mortem observations of the wear track and the counterbodies were carried out by means of Scanning Electron Microscopy (SEM) and profilometer measurements.