Studies on the Sliding Wear Performance of Plasma Spray Ni-20Cr and Ni3Al Coatings

Two metallic powders namely Ni-20Cr and Ni₃Al were coated on the AISI 309 SS steel by shrouded plasma spray process. Subsequently, the coatings were characterized by the XRD and SEM analysis. The wear behavior of the bare, Ni-20Cr and Ni₃Al coated AISI 309 SS steel was investigated according to ASTM Standard G99-03 on a Pin-on-Disc Wear Test Rig. The wear tests were carried out normal loads of 30 N and 50N with a sliding velocity of 1 m/sec. Cumulative wear rate (CWR) and coefficient of friction (m) were calculated for all the cases. The worn-out surfaces were then examined by SEM analysis. Both the as-sprayed coatings exhibited typical splat morphology. The XRD analysis indicated the formation of γ-Ni phase for the Ni-20Cr coating and Ni₃Al phase for the Ni₃Al coating. It has been concluded that the plasma sprayed Ni-20Cr and Ni₃Al coatings can be very useful to reduce the wear rate of AISI 309 SS steel. The coatings were found to be adherent to the substrate steel during the wear tests. The plasma sprayed Ni₃Al coating has been recommended as a better choice to reduce the wear of AISI 309 SS steel, in comparison to the Ni-20Cr coating.