Hot working characteristics of HEXed PM nickel-based superalloy during hot compression
(1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, China;
3. School of Aeronautics and Astronautics, Central South University, Changsha 410083, China;
4. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China)
2. National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, China;
3. School of Aeronautics and Astronautics, Central South University, Changsha 410083, China;
4. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China)
Abstract: To study the hot deformation behavior of a new powder metallurgy nickel-based superalloy, hot compression tests were conducted in the temperature range of 1020-1110 °C with the strain rates of 0.001-1 s-1. It is found that the flow stress of the superalloy decreases with increasing temperature and decreasing strain rate. An accurate constitutive equation is established using a hyperbolic-sine type expression. Moreover, processing map of the alloy is constructed to optimize its hot forging parameters. Three domains of dynamic recrystallization stability and instability regions are identified from the processing map at a strain of 0.7, respectively. The adiabatic shear band, intergranular crack and a combination of intergranular crack and wedge crack are demonstrated to be responsible for the instabilities. Comprehensively analyzing the processing map and microstructure, the optimal isothermal forging conditions for the superalloy is determined to be t=1075-1105 °C and =10-3-10-2.8 s-1.
Key words: powder metallurgy; nickel-based superalloy; hot deformation behavior; constitutive equation; hot processing map; dynamic recrystallization