Grain Boundary Segregation and Mechanical Properties of an Aged Ni-20Cr-18W-1Mo Superalloy at Different Temperatures

The influence of aging temperature (200 to 800 °C) on grain boundary segregations in a Ni-20Cr-18W-1Mo superalloy was investigated by scanning electronic microscope (SEM), transmission electron microscopy (TEM), electron microprobe analyzer (EMPA) and a mechanical testing machine. Results indicate that the grain boundary segregation critical time of sulfur and phosphorus decreases with increasing of the aging temperature. Increasing of the aging temperature has a conspicuous effect on the concentration distribution in the grain boundary and the grain core. Grain boundary concentrations of sulfur and phosphorus increase with raising the testing temperature until a peak value is obtained at 650 and 400 °C, respectively, which is the essential reason to the declined mechanical properties from 200 to 600 °C