Hot deformation behavior of the 1.15C-4.00Cr-3.00V-6.00W-5.00Mo powder metallurgy high speed steel

The deformation behavior of the 1.15C-4.00Cr-3.00V-6.00W-5.00Mo powder metallurgy (PM) high speed steel in hot working process was investigated by the isothermal compression tests carried out at the temperature of 950-1150°C and the strain rate of 0.001-1.0s-1with the height reduction of 60%. True stress-true strain curves are investigated; the hot deformation activation energy of the steel is determined to be 750kJ/mol, and a constitutive equation is obtained. The processing maps were constructed, identification of the instability region and optimization of hot deformation parameters. It is found that the hot working process of the steel can be carried out safely in the domain of (Td: 1000-1150°C, ε·: 0.006-0.1s-1). To obtain the homogeneous microstructure with fine grains, the hot working process should be carried out at the condition of (Topi: 1050°C, ε·opi: 0.1s-1). The flow instability is expected in the two domains at 1030-1150°C/0.1-1.0s-1and 1000-1075°C/0.001-0.006s-1. Furthermore, the true strain takes a great effect on processing maps in which the efficiency of power dissipation obviously changes with the increase of strain from 0.05 to 0.90.