Evaluation of HIP pressure on Inconel 718 superalloy

Abstract

In the companion study 'Effects of temperature of HIP process on characteristics of Inconel 718 superalloy' in the present issue, the temperature parameters for hot isostatic pressing (HIP) of Inconel 718 superalloy were discussed. That study showed that a HIP temperature of 1180°C for Inconel 718 superalloy was optimum. The present study continues to discuss the effects of processing pressure of HIP for Inconel 718 superalloy. Four different HIP pressures were used: 1000, 1500, 1750 and 2000 bar (1 bar = 0·0986 MPa). Meanwhile the HIP temperature was maintained at 1180°C and soaking time was 2 h. To evaluate the effects of HIP pressure for Inconel 718 superalloy, tensile and bending tests at room and high temperature were evaluated. Porosity tests and microstructure inspection were also performed. The results show that 1750 bar of HIP treatment was optimum for Inconel 718 superalloy. It reduced the porosity by 78·5% and decreased the δ phase precipitation for Inconel 718 superalloy. It also increased the tensile strength by 18·48% at room temperature, 13·02% at 540°C, and 20·11% at 650°C. The elongation increased by 33·2% at room temperature, 124·82% at 540°C, and 53·24% at 650°C in tension tests. Finally, the results of three-point bending tests showed that the optimum processing pressure of HIP can enhance the bending strength by 32·45% at room temperature and 17·84% at 540°C.