Study of adhesion of different plasma-sprayed coatings to aluminium

The aim of the work was to determine the bond strength of plasma-sprayed layers to aluminium substrate. The layers of nickel alloy, iron alloy, wolfram carbides with different amounts of nickel were plasma sprayed onto AK12 and PA6 aluminium alloys. The stress affecting the separation of coatings from the substrate was taken into account as the criterion of bond strength. The influence of the substrate surface roughness, the thickness of coatings, the amount of metal binder in carbide layers as well as spraying technique on bond strength were investigated. The microscope observations and sample cross-sections showed very strong adherence of the sprayed layers to aluminium substrates. It was stated that local micro-welds could take place in the layers containing metal. Properly sprayed layers reached bond strength of at least 20 MPa. It was found out that the use of the device providing continuous cleaning of the substrate surface during plasma spraying process significantly increased bond strength and improved coatings structure.