Local wear resistance of Inconel 625 coatings processed by different thermal techniques: A comparative study

Abstract

Ni-base superalloys, like Inconel 625, are extensively used in several applications due to their good performance at high temperature and their corrosion resistance. The high costs of these alloys promote their usage as coatings deposited onto cheaper materials. This practice improves the component performance without an excessive increment in price. Cold Spray (CS) deposition is a relatively new technology that could be considered as a real solid-state coating processing method. Consequently, no oxides are formed during CS deposition and the coatings do not lose their potential oxidation resistance. However, mechanical and tribological behaviour of CS materials is highly dependent on the processing parameters and powder feedstock properties. For these reasons, the aim of this work is to evaluate the mechanical properties and the local wear behaviour of high-pressure CS Inconel 625 coatings deposited under different spraying conditions by using different particle size distributions of powders. Nanoindentation tests were carried out on the coatings with a diamond Berkovich tip which determined the elastic modulus and hardness. Additionally, microscratch tests were also conducted to compute the local wear rate through the estimation of the removed volume. The cross profile of the residual grooves was recorded using the same tip as the one used to make scratch tests. These measurements were checked by Atomic Force Microscopy (AFM) analysis. The values obtained by both techniques were similar in the validation tests. The local wear rates were correlated with the mechanical properties and the scratch micromechanisms which were analysed in the scanning electron microscope. Finally, the results obtained were compared with those corresponding to coatings processed by more traditional methods.