Effect of powder injection distance on microstructure and mechanical properties of reactive plasma sprayed TiCN coatings

In this paper, three different powder injection distances from nozzle exit (− 3, 0 and 4 mm, respectively) were employed to fabricate TiCN coatings using reactive plasma spraying. The effect of powder injector distance on the microstructure and properties of TiCN coatings were systematically evaluated. Results show that all the coatings consist of TiCxN1 − x (0 ≤ x ≤ 1), Ti2O and/or residual graphite phases, and the amount of residual graphite and Ti2O phase increases with the increase of distance. With the increase of distance, the number of unwell-spread particles increases and it results in the morphology changing from relatively flat to uneven. Big pores are more likely to appear around unwell-spread particles. Compared with the coating sprayed at distance of 0 mm or 4 mm, the coating sprayed at − 3 mm exhibits improved mechanical and tribological properties, which are attributed to the high Vickers microhardness and strong bonding strength. The wear mechanism of three TiCN coatings is abrasive wear accompanied with oxidative wear.