Effects of Heat Treatment on Mechanical Properties of Some Nickel-Base Heat-Resisting Alloys

Studies on nickel-base heat-resisting alloys-IV

Abstract

Effects of practical heat treatment shown by Table 1 on mechanical properties of Inconel X-550, Inco 73°, Nimonic 90 and Inco 700 were investigated.
The heat treatment B which contained water cooling after solution-treatment gave higher short-time tensile strength. But in the case of Inco 739 and Inco 700 which contained higher Al than other alloys, the heat treatment F gave the same short time tensile strength at 750°C as the heat treatment B.
The heat treatment of D and F, which contained solution treatment at 1180°C, gave the highest stress rupture strength at 750 and 816°C to Inco 739, Inco 700 and Inconel X-550.
The reason of the above fact was due to softening during long time test at elevated temperature in the case of heat treatment B.
In the same way as Inco 700 heat-treated by D did not show softening during stress rupture test at 816°C, so heat treatment D showed the highest stress rupture strength at this temperature. But as in the case of other alloys, hardness of specimens decreased remarkably by overaging during stress rupture test at 816°C, so effect of heat treatment on stress rupture strength at this temperature were not clearly.
The heat treatment C and E, which contained coarse aging at 980°C, gave lower shorttime tensile strength and stress rupture strength. It was due to the fact that aging at 980°C cause coarse precipitates, and was softened easily at elevated temperature by overaging.