Microstructure and hardness evolution in MAR-M247 Ni-based superalloy processed by controlled cooling and double heat treatment

摘要

This work studies the microstructure and hardness evolution in MAR-M247 Ni-based superalloy pro cessed by controlled cooling and double heat treatment. The solidification experiments with controlled cooling rates in the range of 0.25-10 K/s were carried out using GLEEBLE thermo-mechanical simulator. In the as-solidified material, with increasing cooling rate, grain and carbide size decreased, whereas vol ume fraction of carbides and microhardness increased. The as-solidified samples were subjected to a dou ble heat treatment consisting of solution treatment followed by aging. The double heat treatment did not affect much the microstructure evolved in the sample solidified at 0.25 K/s while it led to dissolution of the γ/MC eutectic in the samples solidified with the cooling rates of 5 and 10 K/s. No significant effect of the double heat treatment on grain size, size and volume fraction of carbides is seen in all samples. The processing - microstructure-microhardness relationship in the material is discussed.