Influence of initial Ti particle size on microstructure and fracture toughness of reactive plasma sprayed TiCN coatings

TiCN coatings were fabricated by reactive plasma spraying (RPS) using Ti-graphite feedstocks with different initial Ti particle size. The microstructure and fracture toughness of the coatings were investigated. The results show that the coatings consist of TiCN, Ti2O and amorphous C and CNx phases. TiCN coatings present some partial-melted particles, un-melted particles, pores, voids and cracks. As the increase of the Ti particle size, the number of un-melted particles increases and the morphology changes from relatively flat to uneven. Compared with the coating sprayed with Ti particle size of 14 μm or 48 μm, the coating with Ti of 28 μm has a higher strength-toughness. This is due to the relative more amounts of TiCN solid solution and close-grained continuous structure.