Optimization of the HVOF Spray Deposition of Ni3Al Coatings on Stainless Steel

To supply wear-resistant coatings on AISI 310 austenitic stainless steel for harsh industry applications, Ni3Al intermetallic compound coatings were prepared by high-velocity oxygen fuel (HVOF) spraying. Ni3Al coatings were deposited under different oxygen/fuel ratios of 4.45, 4.89 and 5.34. The phase structure, microstructure, mechanical and tribological properties of the coatings at 25 °C were investigated firstly. As a result, the HVOF oxygen/fuel ratio of 4.89 was chosen to get the best physical properties of an average porosity 1.0 vol.%, thickness 290 μm, hardness 527 ± 16 HV, friction coefficient 0.75 and wear rate 1.74 × 10− 5 mm3/(N·m). Then tribological tests across a wide temperature range from 25 to 800 °C were carried out on the optimized coating: the coating presented the highest anti-friction and wear resistance at 600 °C, a continuous and dense oxide layer comprised of NiO, Ni2O3, Al2O3 and NiAl2O4 was formed and acted as a solid lubricant, and contributed a relatively low friction coefficient of 0.57 and wear rate of 8.91 × 10− 5 mm3/(N·m). The wear mechanisms were mainly tribo-oxidation wear and slight abrasive wear.