Interface characterization of Cu–Mo coating deposited on Ti–Al alloys by arc spraying

Abstract

Cu – Mo pseudobinary alloys are promising candidates as electrode materials in CoSb 3-based skutterudite thermoelectric (TE) devices for TE power generation. In this study, Cu – Mo coatings were deposited onto Ti – Al substrates by applying a dual-wire electric arc spraying coating technique. The microstructure of the surfaces, cross sections and coating interfaces were analyzed by scanning electron microscopy (SEM) and energy dispersion spectrometry (EDS). Cu – Mo coatings showed a typical banded splat with compact microstructures, and have no coarse pores nor micro-cracks. The thermal shock resistance of the Cu – Mo coating was also investigated to show good combinations with Ti – Al substrates. After 50 thermal shock cycles, there were no cracks observed at the interface. In contrast, the test of the thermal shock resistance of the Cu coating on the Ti – Al substrate was also investigated. Due to a large difference in the thermal expansion coefficients between Cu and Ti – Al alloys, the Cu coating flaked from the Ti – Al substrate completely after 10 thermal shock cycles. The contact resistivity of the Ti – Al / Cu – Mo interface was about 1.6 μΩ⋅cm2 and this value was unchanged after 50 thermal shock cycles, indicating the low electric resistance and high thermal stability of the Cu – Mo / Ti – Al interface.