Effect of carbide size and spacing on the fretting wear behavior of Inconel 690 SG tube mated with SUS 409

The effect of carbide size and spacing on the fretting wear resistance of Inconel 690 steam generator (SG) tube mated with SUS 409 was investigated in this study. Based on previous materials tribology research, we reasoned that increasing carbide size and spacing would increase the wear resistance of the Inconel 690. Experiments were performed to test this hypothesis. Commercialized Inconel 690 tube with mean carbide length, thickness and spacing of 0.29, 0.10, and 0.59 μm, respectively, was used for the wear test. Carbide length, thickness, and spacing increased to 0.36, 0.15, and 0.68 μm, respectively after heat treatment at 450 °C for 16 h without changes in carbide volume fraction, grain size or hardness. The results of the wear test showed that at the amplitude of 25 μm, wear coefficient did not change due to stick phenomenon. At the amplitude of 50 μm-150 μm, wear coefficient decreased about 50%. At the amplitude of 300 μm, the wear coefficient decreased from 2.7×10−13m3/Nm to 2.0×10−13m3/Nm due to increase in carbide size and spacing.