Tribological behavior of NiAl coating deposited by plasma spraying of diamond-contained Ni/Al composite powder at a wide range temperature from 25 °C to 700 °C

NiAl intermetallics are widely used as high temperatutre materials especially as corrosion- and oxidation-resistant coatings, and could be also expected as high temperature anti-tribological wear coating. In this study, NiAl coating containing graphite and nano-diamond, being referred to as a “NiAl-C coating, is prepared by atmospheric plasma spraying (APS) of Ni/Al/diamond composite powder. The microstructure, phase composition and mechanical properties of the coatings are characterized in comparison with traditional APS NiAl coating. The friction and wear behavior of the NiAl-based coatings is evaluated using a ball-on-disk high temperature tribometer from 25 °C to 700 °C. Results show that the NiAl-C coating presents a higher adhesive strength (55.7 MPa) due to low oxide inclusions in comparison with the traditional APS NiAl coating (30.9 MPa). Moreover, the NiAl-C coating presents significantly lower friction coefficient and wear rate in the tested temperature range. The graphite and nano-diamonds in the coating retained from the starting powder effectively improve the tribological wear performance of the NiAl-C coating in a wide temperature range through their solid lubricating features. Moreover, it was found that the NiO and Al 2 O 3 particles which are evolved during sliding against counterpart ceramics at the temperature higher than 400°C benefit lubrication. Thus, the present NiAl-C presents an effective self-lubricating effect in a wide temperature range from ambient room temperature to 700°C which is attributed to graphite and nano-diamonds along with the in-situ evolved oxides. Therefore, the APS NiAl-C coating is promising for the applications of high temperature tribological environments.