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

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 degrees C. The results indicated that the yield strength was anomaly with increasing temperature. Below 600 degrees C, both the tensile and yield strength decreased slightly with increasing temperature; above 600 degrees C, the tensile strength decreased rapidly while the yield strength almost kept invariable; the elongation had its minimum value at 600 degrees C. Microstructure analysis showed that M23C6 carbides including of lamellar carbides (600 degrees C) and discrete carbides (above 600 degrees C) precipitated at the grain boundaries. The lamellar M23C6 carbides with the width of 1-3 mu m 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 M23C6 carbides. TEM analysis showed that the high dislocation density and cross-slip also contributed to the yield strength anomalous. (C) 2010 Elsevier B.V. All rights reserved.