Tribological Behaviors of Ni₃Al-Based Coating Coupled with Different Counterpart Materials in Wide Temperature Range

The Ni₃Al based composite coating was prepared by plasma spraying. The influences of 316L and Al₂O₃ counterpart material on the tribological behaviors of the coating at 25 ℃ to 800 ℃ were investigated. The results showed that under the synergistic action of precipitation of soft metal Ag, brittle-plastic transformation of BaF₂/CaF₂ and tribo-oxidation, the friction coefficient and wear rate of Ni₃Al/316L and Ni₃Al/Al₂O₃ tribo-pairs had the similar trend with the increase of temperature, and the Ni₃Al/Al₂O₃ tribo-pairs had better performance. At 25 ℃, the coating coupled with 316L adhesive wear and abrasive wear occurred, while brittle peeling and abrasive wear occurred when the coating coupled with Al₂O₃ of high hardness, resulting in rougher coating surface and higher friction coefficient. However, the thermal conductivity of Al₂O₃ was low, and a large amount of frictional heat generated under the action of high contact stress cannot be dissipated rapidly. The stripped material was stored in the peeling hole or adhered to the worn surface, resulting in a lower wear rate of Ni₃Al/Al₂O₃ friction pair. At 200~600 ℃, the Al₂O₃ of high hardness had a strong plough effect on the coating, resulting in a higher friction coefficient of Ni₃Al/Al₂O₃ friction pair. Meanwhile, Al₂O₃ promoted the plastic deformation of the coating, inhibited the fatigue stripping of the material, and made the coating with lower wear rate. At 800 ℃, the high hardness of Al₂O₃ promoted the formation of a lubrication film with high oxide content on the worn surface, so that the Ni₃Al/Al₂O₃ friction pair had low friction coefficient but high wear rate.