Tribological behaviors of arc sprayed NiCrMoAl alloy coating after heat treatments

Abstract

The influence of heat treatments on tribological behaviors of arc-sprayed NiCrMoAl alloy coating were studied. The NiCrMoAl alloy coating was heat-treated at 300–700 °C for 10 and 30 days. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS) were used to study the microstructure and chemical composition. Vickers's hardness and ball-on-disk testing are used to evaluate the mechanical properties of the coating at room temperature. The heat treatment at 600 °C for 30 days led to an increase in the hardness of coatings of upto 155% compared to as-sprayed coating, due to formation of MoSi2 and oxides. The solid solution strengthening in the splats was reduced after heat treatment at a high temperature of 700 °C for 10 and 30 days at the expense of MoSi2 formation. Among heat-treated coatings, heat treatment at 600 °C for 10 days led to the lowest wear rate, whereas this was 20% higher than that of the as-sprayed coating. Moreover, the oxide content after the heat treatment at elevated temperature induced the microvoid and enhanced three-body abrasive wear due to the oxides pull-out of the coating. Therefore, a long heat treatment time, 10 and 30 days caused the poor tribological behavior of the NiCrMoAl alloy coating due to three-body abrasive wear.