2015 Volume 56 Issue 5 Pages 720-725
Effect of carbon (C) content on heat treatment behavior of multi-alloyed white cast irons with basic alloy composition was investigated. The multi-alloyed white cast irons with varying C content of 1.73–2.34% were prepared. After annealing, the test specimens were austenitized at 1323 and 1373 K, and then hardened by fan air cooling. The hardened specimens were tempered between 673 and 873 K. It was found that the hardness in as-hardened state increased first and then decreased as C content increased. The volume fraction of retained austenite (Vγ) increased with increasing C content. In tempered state, each hardness curve showed secondary hardening due to the precipitation of secondary carbides as well as the transformation of decomposed austenite to martensite during post cooling. The Vγ began to decrease greatly when the tempering temperature was elevated over 723 K. The maximum tempered hardness (HTmax) was obtained in the specimens tempered between 798 K and 823 K where the Vγ ranged from 8 to 12%. The highest value of HTmax was obtained in the 2.00% C specimen hardened from 1373 K austenitizing and in the 2.34% C specimen hardened from 1323 K austenitizing.