Abstract:True stress-true strain curves of Incoloy028 alloy at high temperature and strain rate were investigated by hot compression test. These curves show that the maximum flow stress decreases with the increase in temperature and the decrease in strain rate. FEM simulation was employed to investigate the influence of temperature, extrusion speed and friction coefficient on the extrusion load, stress, strain and strain rate in the extrusion process. The increase of extrusion temperature results in decrease of load and deformation resistance, but has little influence on strain and strain rate. When extrusion speed changes between 200 and 350 mm/s, no obvious change about extrusion load can be found. Sharp peak value up to 42500 kN emerges in the extrusion load curve and the extrusion process becomes unstable seriously when extrusion speed rises up to 400 mm/s. Both stress and strain rate increase with the raise of extrusion speed. When friction coefficient is between 0.02 and 0.03, deformation resistance is about 160 MPa and the strain rate can be limited below 70 s-1. Successful production of Incoloy028 tube verifies the optimized parameters by FEM simulation analysis, and mechanical tests results of the products meet the required properties.

Key words: Incoloy028 alloy; hot extrusion; compression; process parameter; FEM simulation