Effects of Fe addition on the microstructure and corrosion properties of quasicrystalline Al-Cu-Fe coatings

Abstract

The performance of material surface under wear and corrosion environments cannot be fulfilled by the conventional surface modifications and coatings. Therefore, different industrial sectors need an alternative technique for enhanced surface properties. Titanium and its alloys possess poor tribological properties which limit their use in certain industries. This paper focuses on the effect of hybrid coatings Al-Cu-Fe on a grade five titanium alloy using laser metal deposition (LMD) process. Icosahedral Al-Cu-Fe as quasicrystals are a relatively new class of materials which exhibit unusual atomic structure and useful physical and chemical properties. A 3kW continuous wave ytterbium laser system (YLS) attached to a KUKA robot which controls the movement of the cladding process was utilized for the fabrication of the coatings. The titanium cladded surfaces were investigated for its microstructure and corrosion properties at different laser processing conditions. The samples were cut to corrosion coupons and immersed into 3.5% NaCl solution at 28oC using Linear Polarization (LP) techniques. The cross-sectional view of the samples was analysed. It was found that the geometrical properties of the deposits such as width, height and the Heat Affected Zone (HAZ) of each sample remarkably increased with increasing laser power due to the laser-material interaction. It was observed that there are higher number of aluminium and titanium presented in the formation of the composite. The cladded layer showed a uniform crack free surface due to optimized laser process parameters which led to the refinement of the coatings. Sample Al-Cu-5Fe showed increase of 1538.3-times the polarization resistance of the substrate (Ti-6Al-4V alloy). Large amount of aluminium and less amount of iron favour the chemical performance of composite thereby increasing the polarization resistance.