Superhard, erosion resistant nanocomposite coatings for practical applications

In this presentation, superhard, erosion resistant nanocomposite coatings developed at Southwest Research Institute (SwRI^®) will be presented.  A plasma enhanced magnetron sputtering (PEMS) process was used for the development, in which Ti was sputtered from targets while a gas mixture of Ar, N₂ and TMS (trimethylsilane) was fed into the vacuum system to form the TiSiCN coatings.  Thick coatings (typically ~ 20-30 micrometer) were obtained and they exhibited a dense structure, good adhesion to the substrate, low internal stress and superior mechanical properties compared to most commercial. The coatings have a microstructure composed of nanocrystalline TiC_xN_1-x (x=0, 0.3 or 0.7) with the grain size of 4-10 nm in a matrix of amorphous SiC_yN_z. The microstructure of the coatings results in the super-hardness (up to 4600HV).  However, the internal stress was found to be less than 1 GPa, thereby allowing the deposition of ultra-thick coatings of over 500 µm.  The coatings also have high values of H³/E^*2 and H/E^*, which have been correlated to the high toughness of the coating. The nanocomposite coatings have been developed for severe environments including sand erosion, sand abrasion, water droplet erosion, and heavy load sliding wear. The coatings have been deposited on various alloy substrates including Ti-6Al-4V, Inconel 718, H-13, 17-4PH, Custom 450 SS, 304 SS, carbon steels and many others. These coatings have found industrial applications including compressor blades or vanes for aero engines; piston rings, cylinder liners and stamping dies for automotive; and ball valves, valve stems, valve seats and plungers the for oil and gas industry. In this paper we review the method for preparing these coatings, discuss their microstructural, mechanical and tribological properties, and present examples for practical applications.

Keywords: Superhard, nanocomposite, coating, erosion resistance, abrasion resistance