LAUSR

Abstract TiCN coatings were reactive plasma sprayed with different Ti/graphite powder ratios. Their crystallization behaviours were investigated. The results showed that the TiN coating consisted of TiN and TiN0.3O phases. With the decrease in the Ti/graphite ratios, the phases in the coatings changed from TiC0.7N0.3+TiC0.3N0.7+amorphous (Ti:graphite = (6-10):1) to TiC0.3N0.7 + TiC + amorphous (Ti:graphite = 4:1). The surface of the TiN coating exhibited the columnar crystals. With the decrease in the Ti/graphite ratios, the columnar crystals gradually skewed towards the surface. The cross-section crystalline morphologies of all the coatings exhibited the layer-layer columnar crystals with better bonding interfaces between the layers. The micro-hardness of the sprayed TiN coating was 1000 HV0.1. The micro-hardness of the TiCN coatings increased with the decrease in the Ti/graphite ratios. The maximum microhardness (1315 HV0.1) was observed at a Ti/graphite ratio of 4:1, approximately 30% higher than that of the TiN coating. The increase in the micro-hardness was correlated with the phase composition and crystalline morphologies.