Effect of Tungsten Equivalent on Heat Treatment Behavior of Semi-multi-alloyed White Cast Iron for Abrasive Wear Resistance

Abstract

In this research, the effect of tungsten equivalent (Weq) on hardness and volume fraction of retained austenite (Vγ) of heat-treated semi-multi-alloyed white cast irons was investigated. Cast irons with 5.0 to 6.6%Weq under 2%C, 3%Cr, 1%W and 5%V were prepared. After annealing, the test specimens were hardened from austenitizing temperatures at 1050 °C and 1100 °C by fan air cooling. The tempering was carried out between 400 and 600 °C. In as-hardened state, the hardness dropped progressively as the Weq rose. High austenitizing temperature provided low hardness. The Vγ increased continuously as the Weq increased, and more Vγ was obtained by hardening from 1100 °C. In tempered state, the hardness curves showed an evident secondary hardening due to the precipitation of secondary carbides and the transformation of retained austenite to martensite. The degree of secondary hardening increased with a rise of Weq value and austenitizing temperature. The maximum tempered hardness (HTmax) was obtained by tempering at 500 °C in all the specimens regardless of austenitizing temperature. The highest values of HTmax, 830 HV30, was obtained in the specimen with 5.0%Weq hardened from 1100 °C.