Mechanical and tribological properties of cold sprayed composite Al-B₄C coatings

Composite aluminum matrix coatings with different content (0-72 vol.%) and size (17 and 75 µm) of B4C in the feedstock were deposited using the cold spray method. The analysis of the microstructure of the coatings was carried out using an SEM and XRD. The microhardness and adhesion strength of the sprayed coatings were measured, and sliding wear tests were carried out. It was shown that the same content in the feedstock, the larger carbide powder corresponds to its higher content in the coating. With the same boron carbide content in the coating, higher microhardness values correspond to coatings obtained from mixtures with fine carbide powder. Coatings sprayed from two different boron carbide powders at the same content in the powder correspond to approximately the same values of adhesion strength. For composite coatings with coarse ceramic powder, the volume loss decreases by about 2–3 times as compared with an aluminum coating. For coatings with fine powder, this effect is less pronounced. The presence of a fine ceramic powder in the coating has practically no effect on coefficients of friction, which turn out to be very close to the values for a coating of pure aluminum. The presence of coarse ceramic powder in the coating, regardless of its content, leads to a noticeable decrease in coefficients of friction.