Ni-based coating protection of 316L stainless steel at dry, elevated temperature and wet sliding condition

Abstract

The NiCrSiB coatings are used extensively for wear and oxidation resistance in numerous applications like hot forming industries, power generation plants, petroleum refining, and nuclear power plants. In this paper, NiCrSiB powder deposited by APS (atmospheric plasma spray) and HVOF (high velocity oxy-fuel) process on stainless steel 316L substrate was investigated for the friction and wear at RT (room temperature), 700 °C, at the lubricating condition with clean and contaminated oil with nano alumina particles. The sliding wear tests were carried out on standard tribometer against silicon nitride (1580 HV0.3) counter material following ASTM G99 standard. The coatings characterization was performed using porosity analysis, nano-indentation, 3D non-contact analysis, EDX (energy-dispersive X-ray), SEM (scanning electron microscope) and LRS (Laser Raman Spectrum). The wear, friction and the wear mechanisms were investigated for both coatings at tested conditions. Although the coating wear was substantially affected by the temperature, the specific wear rate of the APS and HVOF coatings lies in the range 10-4 to 10-5 mm3/N.m and hence serviceable up to 700 °C. The coating's wear mechanisms at elevated temperature were a combination of adhesive and tribo-oxidative wear. At the dry, wet, and high-temperature condition, the HVOF coating retains higher wear resistance than APS coating, due to the high dense structure, low porosity, low inflight oxidation and high nano hardness. The nano alumina particles in the contaminated oil reduces the COF significantly for HVOF coating whereas, negligible change in COF has been observed for APS coating.