The Effect of Sub-Critical Heat Treatment on Hardness, Retained Austenite and Abrasive Wear Resistance of Hypoeutectic 16 mass% Cr-2 mass% Mo Cast Iron with Varying Vanadium Content

Abstract

To increase the matrix hardness without complete hardening, a sub-critical heat treatment was performed by holding the as-cast iron below the pearlite transformation temperature (A1), and exposed to a hypoeutectic 16 mass% Cr-2 mass% Mo cast iron with a 03 mass% vanadium (V). The temperatures were held between 723K and 923K with 50K intervals for 14.443.2 ks and then cooled via air from a fan. In the as-cast state, the hardness of the cast iron increased progressively and the volume fraction of retained austenite (V£) decreased gradually as the V content of specimen rose. With the sub-critical heat treatment, the hardness increased initially and then decreased with an increase in holding temperature. Conversely, the V£ was reduced greatly when the holding temperature was elevated above 823 K. The maximum hardness in the sub-critical heat treatment (HSTmax) was obtained in the temperature range of 823873 K, while the V£ values were approximately 2030%. The largest HSTmax value of 830 HV30 was obtained in the specimen with 3 mass% V. The abrasive wear resistance was evaluated by a Suga abrasion wear tester using the specimens heat-treated at selected conditions. The wear resistance increased as the V content increased with the highest wear resistance obtained in the specimens with HSTmax.