Two-body abrasive wear of nano- and microcrystalline TiC–Ni-based thermal spray coatings

In the present study, the wear behaviour of nanocrystalline coatings of the composition (Ti,Mo)(C,N)–45 vol. % NiCo, prepared by vacuum plasma spraying (VPS) and high-velocity oxy-fuel (HVOF) spraying of high-energy-milled powder, is characterized and compared to microcrystalline coatings of the same composition. Two-body abrasive wear tests, as well as scratch tests, are applied to produce wear traces on the surfaces of the nano- and microcrystalline coatings. While nanocrystalline HVOF coatings are weaker than their microcrystalline counterparts, nanocrystalline VPS coatings show superior wear resistance. The worn surface morphologies are investigated with optical microscopy, scanning electron microscopy and atomic force microscopy. The wear mechanisms and failure of nano- and microcrystalline coatings are distinctly different and are discussed in detail.