Tribological Characterization of N 80A and 21-4N Valve Materials Against GGG-40 Seat Material Under Dry Sliding Conditions at Temperatures Up To 500 °C

Abstract

Friction and wear studies of Nimonic 80A and 21-4N valve materials against GGG-40 under dry sliding conditions, at temperatures ranging from 50 °C to 500 °C, are presented in this paper. Friction coefficient was found to be continuously decreased with time for all tests with prominent running-in behavior seen in the 50 °C and 500 °C tests. Higher friction coefficient and wear were observed at 300 °C as compared to those at 50 °C and 500 °C. Formation of oxide Fe3O4, at 300 °C, was confirmed by Raman spectroscopy, which resulted in a higher friction coefficient and wear. Raman spectroscopy further revealed the presence of α-Fe2O3, hematite, in most cases, with the presence of oxides of Ni–Cr and Ni–Fe as well. Energy dispersive spectroscopy (EDS) results on the samples confirmed the same. Wear at 500 °C was found to be the least for both the valve materials with scanning electron microscopy (SEM) confirming the formation of well-developed glaze layers.