Effect of temperature on tensile behavior of Ni–Cr–W based superalloy

Abstract

The temperature dependence of tensile behavior of Ni–Cr–W based superalloy has been studied by tensile tests in the temperature range of 25–900 °C. The results indicated that the yield strength was anomaly with increasing temperature. Below 600 °C, both the tensile and yield strength decreased slightly with increasing temperature; above 600 °C, the tensile strength decreased rapidly while the yield strength almost kept invariable; the elongation had its minimum value at 600 °C. Microstructure analysis showed that M 23C 6 carbides including of lamellar carbides (600 °C) and discrete carbides (above 600 °C) precipitated at the grain boundaries. The lamellar M 23C 6 carbides with the width of 1–3 μm weakened the strength of grain boundary, and thus led to the premature failure of the alloy. But the grain boundary sliding was effectively restricted by discrete M 23C 6 carbides. TEM analysis showed that the high dislocation density and cross-slip also contributed to the yield strength anomalous.