Dry sliding wear of a Ni-based superalloy as a function of the aging time.

From the present work, the wear behavior of aged Ni-based superalloy was analyzed under dry sliding conditions. Such alloy was melted in a vacuum induction furnace and cast into a ceramic mold. Then the alloy was solubilized at 1080°C for 4 hours and then aged at 760°C for 4, 8, 16, 24, 48, 72 and 150 hours. The alloy was characterized as-cast and also in the heat-treated conditions by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Mechanical characterization included just Vickers hardness and wear resistance under dry sliding conditions by a block on ring configuration according to the ASTM G77 standard. Wear tests were undertaken for 2000 m at a speed of 0.7 ms−1 at two different loads (25 and 78 N). The worn samples were analyzed by an optical profiler to determine the wear volume and by SEM to analyze the worn surface and the microstructure below the worn surface. The main findings indicate the formation of an oxide layer mainly formed by Cr and Ni during sliding. The thickness of such a layer is about 10 μm for short aging times and about 5 μm for longer aging times. For this load, the wear resistance was 50% higher for the shorter aging times than that for the longer aging times. This behavior is described in terms of the thickness of the protecting layer, and on the availability of chromium to form such a layer since it forms Cr23C6 at long aging times. On the other hand, for a load of 78 N the wear behavior is in agreement with hardness. Wear resistance increases with aging time due to the higher precipitation of prime gamma phase.