Solidification behaviour and hot cracking susceptibility of a novel Ni-based superalloy

A novel Ni-based superalloy GH4151, with a γ′ volume fraction of about 55% and a service temperature capability up to 800 °C, was investigated. Due to the different cooling conditions of various regions during the solidification of ingots, significant cooling rate variations may lead to the occurrence of hot cracking. Conventional scanning laser microscope was utilised to investigate the solidification process and phase precipitation behaviour of the GH4151 under wide range cooling rates. The characteristics of L → γ transformation were analysed, and the growth rates of γ at each stage were calculated. The segregation behaviour was predicted using the Scheil equation, and the predicted results match well with the experimental results. The sensitivity coefficient for hot cracking was modified, and cracking sensitivity coefficient values for the alloy under different cooling rates were computed, revealing that the alloy is most susceptible to hot cracking at 10 °C/min cooling rate. Therefore, controlling the cooling rate can reduce the possibility of hot cracking in ingot.