The effect of surface preparation on high temperature oxidation of Ni, Cu and Ni-Cu alloy

Abstract

In the present paper, the analysis of polishing, grinding and sand-blasting processes on oxidation behavior of nickel, copper and Ni30Cu70 alloy has been performed for three different temperatures. Surface roughness has been analyzed using two methods: contact profilometer and fractal analysis. It has been proved that Ra parameter for sand-blasted samples is greater about one order of magnitude from ground and two order of magnitude from polished samples. Obtained mass gain plots after isothermal oxidation tests, SEM microphotographs and SEM/EDS analysis of the samples prove that morphology of the polished and ground samples does not vary significantly after oxidation at investigated temperatures, but differences in oxide layer thicknesses and mass gains were observed. Oxidized sand-blasted samples revealed that increased surface roughness and alumina intrusions remained in the surface after sand-blasting process change the oxidation process–mixed Al/(Ni, Cu or Ni-Cu) oxide is formed and separate Al2O3 particles are visible. Moreover, differences in thickness ratio of copper oxides: Cu2O to CuO on copper samples oxidized at 750 °C (26, 20; 29, 64; 43, 45 for polished, ground and sand-blasted samples, respectively) prove that surface preparation influence high-temperature oxidation of the samples by promoting new diffusion mechanism.