Oxy-acetylene flame thermal sprayed coatings of aluminium matrix composites reinforced with MoSi2 intermetallic particles

Oxyacetylene flame spraying technique has been used to manufacture Al/MoSi2 composite coatings by using mixtures of powders of Al and MoSi2. Coatings with up to 8% of MoSi2 and porosity of 3% were obtained after optimizing the main spraying variables: powder feeding rate, number of layers, spraying distance and preheating of the substrate. To evaluate the role played by each variable, the hardness and the microstructure of the coatings were measured; including the degree of reinforcement and porosity. Different coatings were tested: as-sprayed and after being cold pressed in order to reduce their porosity. The wear behavior of the coatings was evaluated by means of pin-on-disk wear tests at different loads. The coatings obtained showed a wear behavior that was better than those obtained by aluminium coatings and similar to Al/SiC composites coatings manufactured by similar processes, but were less abrasive to the counterbody.