Effect of adding soft Bi2O3 on structural modification and tribological regulation of Ni-5 wt% Al composite coating in wide temperatures range

Abstract

An alternative process to fabricate Ni-5 wt% Al-Bi2O3 composite coatings was developed through the atmospheric plasma spraying technique. The influence of soft Bi2O3 additions on tailoring microstructure and tribological behavior of resulting Ni-5 wt% Al-Bi2O3 composite coating was investigated over a broad range of temperatures. As the Bi2O3 inclusion within the Ni-based matrix gradually increased, the obtained Ni-5 wt% Al-Bi2O3 composite coatings featured as the increasingly compact laminated hierarchy. This was, however, compromised with no significant improvement in mechanical capabilities. All Ni-5 wt% Al-Bi2O3 composite coatings demonstrated the temperature-mediated frictional characteristic. Nevertheless, wear aggravation occurred for as-received composite coatings at the medium temperatures. It was noteworthy that Ni-5 wt% Al-Bi2O3 composite coatings entailed superior lubrication at 800 °C, which was intrinsically associated with the lubricious constituents primarily consisting of Bi2O3 and NiO on the sliding surface. The influential factor of temperature and Bi2O3 on varying friction and wear for Ni-5 wt%. Al-Bi2O3 composite coating was discussed from the perspective of tribochemically oxidative interactions between the rubbing contacts.