2016 Volume 57 Issue 2 Pages 174-182
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 0–3 mass% vanadium (V). The temperatures were held between 723 K and 923 K with 50 K intervals for 14.4–43.2 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 (Vγ) 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 Vγ 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 823–873 K, while the Vγ values were approximately 20–30%. 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.
