Effect of repeated tempering on abrasive wear behavior of hypoeutectic 16 mass% Cr cast iron with molybdenum

Abstract

The effects of hardness, volume fraction of retained austenite (Vγ) and the number of tempering (tN) on abrasive wear resistance of hypoeutectic 16 mass% Cr cast irons without and with Mo was investigated. After annealing, the specimens were austenitized at 1323K for 5.4 ks and cooled by fan air cooling. The hardened specimen was repeatedly tempered, at most three times at 748798K for 7.2 ks. The abrasive wear resistance of heat-treated specimens was evaluated using a Suga wear tester (two-body-type abrasive test). In the as-hardened state, the hardness did not change but the Vγ increased gradually with an increase in the Mo content. In the tempered state, the hardness curves showed a secondary hardening as the tN increased due to the precipitation of secondary carbides and transformation of destabilized austenite to martensite. The wear loss increased in proportion to the wear distance in all specimens. The wear rate (Rw) varied depending on the tN and Mo content. The Rw decreased when the hardness was increased. The Rw increased first and then decreased as the tN increased. The highest wear resistance was obtained in the 3% Mo cast iron with triple tempering. © 2012 The Japan Institute of Metals.