Use of microhardness as a simple means of estimating relative wear resistance of carbide thermal spray coatings: Part 2, wear resistance of cemented carbide coatings

A selection of WC-Co and Cr₃C₂-25%NiCr coatings produced by plasma spray and high velocity oxygen fuel (HVOF) deposition techniques were subjected to various wear tests designed to simulate abrasions, cavitation, sliding, and particle erosion type wear mechanisms. All of the coatings were at least 200 μm thick and were deposited onto stainless steel substrates. In Part 1 of this contribution, the microstructures of the coatings were characterized and their mechanical properties were assessed using microindentation procedures. In this second part of the article, the behavior of the coatings when subjected to the various wear tests is reported and the utility of microhardness testing as an indication of relative wear resistance is discussed. It is shown that correctly performed, appropriate microhardness measurements are a good indication of abrasion resistance and sliding wear resistance, and also correlate well with cavitation resistance in Cr₃C₂-NiCr, The measurements were less useful for predicting erosion resistance for both Cr₃C₂-NiCr and WC-Co, however, and for abrasion resistance when WC-Co was ground against SiC. Here the contribution of micro-mechanism involving fracturing and brittle failure is greater than indicated by the coating microhardness, which is essentially a measurement of resistance to plastic deformation under equilibrium conditions.