Manish Roy and Andreas Pauschitz¹

Defence Metallurgical Research Laboratory

PO: Kanchanbagh, Hyderabad: 500 058, India

¹ Austrian Centre for Competence of Tribology

Wiener Naustad, Victor Kplan Strabe, Austria

Abstract

Cermets variety of coating such as WC-Co, Cr_xC_y-NiCr, obtained by thermal spraying is well known for its excellent tribological properties. WC-Co provides excellent performances at ambient temperature. However, at elevated temperature, the synergistic effect of wear and oxidation degrades its performance. This limits the application of this coating up to 625 K. In contrast, Cr₂C₃-20NiCr is employed at elevated temperature up to 1173 K for its excellent oxidation resistance and reasonable wear resistance. This coating also finds application at ambient temperature where wear resistance in corroding environment is required. In view of the above, the objective of the present investigation is to examine the elevated temperature wear of thermal sprayed nanocrystalline Cr₂C₃-20NiCr coating deposited on Ni based dispersion strengthened alloy PM 1000. Towards that purpose the said coating is deposited on PM–1000 alloy. The sliding wear behaviours of the coating and the substrate were studied for five different temperatures from room temperature to 1073 K. The results showed that the nanocrystalline Cr₂C₃-20NiCr coating and PM 1000 alloy have comparable friction coefficient up to 673 K. The nanocrystalline Cr₂C₃-20NiCr coating has lower friction coefficient than PM 1000 alloy beyond 673 K. The wear behaviour exhibited that the coating shows thickness gain at ambient temperature. At elevated temperature the coating experiences thickness loss. In contrast, PM 1000 alloy exhibited thickness gain at all temperatures. The morphologies of the worn surfaces and the transverse sections of the worn surfaces are examined. Formation of various types of layer depending on the temperature of wear is noted. The details of the results will be discussed and presented.