Microstructure and wear behavior of nano C-rich TiCN coatings fabricated by reactive plasma spraying with Ti-graphite powders

• Nano TiCN coatings were synthesized by air plasma spraying method with graphite as carbon source.
• The as-obtained coatings contained mainly TiC0.7N0.3 phase with some residual graphite.
• TiC0.7N0.3 coatings exhibited higher hardness and better wear resistance than TiN coatings.

In the present study, nanostructured titanium carbonitride (TiCN) coatings were prepared by reactive plasma spray (RPS) from Ti-graphite powders under nitrogen atmosphere. The phase composition, microstructure and wear resistance of the TiCN coatings were characterized by X-ray diffractometer (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscope (TEM), microhardness tester and block-on-ring tribometer. Results showed that the as-obtained coatings are mainly consisted of C-rich TiC0.7N0.3 phase. The occurrence of C-sp2 bond indicated the existence of residual graphite in TiC0.7N0.3 coatings. The coating exhibited a typical nanostructure including 90 nm equiaxed grains. The as-obtained TiCN coating had the hardness of ~ 1674 HV and exhibited better wear resistance than TiN coatings, showing low coefficient of friction of 0.28 under 980 N. The wear mechanism of TiCN coatings showed the mixture of adhesive wear and oxide wear under low load while mainly abrasive wear under heavy load.