Wear behavior of Al–12Si/TiB2 coatings produced by laser cladding

Composite coatings consisting of an Al–12Si alloy matrix reinforced with TiB2 particles were prepared by laser cladding, from mixtures of Al–12Si alloy and TiB2 powders. The coatingʹs microstructure is composed of TiB2 particles dispersed in a matrix consisting of proeutectic α-Al dendrites and α-Al + Si eutectic. The coatings present a hardness of 156 HV and a wear coefficient of 2.65 × 10−5 mm3/(Nm) in dry sliding wear tests, with a counterbody of AISI 440 C tool steel. The interaction between the sample and the counterbody leads to the formation of a tribolayer containing of a large proportion of oxides of the elements both of the sample and of the counterbody. The formation of this tribolayer can be explained by the oxidation of the tribological pair materials due to the high flash temperatures generated during asperity interactions, followed by cracking of the oxides and consolidation of the debris into a compact surface layer which protects the coating from further wear. Repeated loading causes cracking of the tribolayer and its delamination as the main material removal mechanism.