Effect of heat treatment on properties of cold sprayed Al-B4C composite coatings

The effect of heat treatment of Al-matrix coatings with different B4C content cold sprayed on stainless steel substrates on their microstructure and properties was studied. Mixtures of aluminum with boron carbide contents of 30, 50, and 70 wt.% were used as a starting powder for coatings deposition. Heat treatment of the coatings was performed in a furnace in Ar atmosphere for 2 h at 400 °C. Heat treatment had no visible effect on the coatings structure. Heat treatment allowed to reduce the microhardness in comparison with as-sprayed coatings, which can be explained by grain growth of aluminum and reduction in dislocations. The bonding strength of the coating obtained from mixture with 30 wt.% B4C after heat treatment practically does not change and is comparable to the bonding strength of the as-deposited coating. Annealed coatings produced from mixtures with 50 and 70 wt.% B4C are characterized by reduced bonding strength in comparison with as-sprayed coatings.