Improving die tooling properties by spraying TiC-Ti-Al and TiB₂-Ti-Al electro-explosive coatings

This article describes increasing wear resistance of 5CrNiMo die steel by more than 5 times. This effect is achieved by creating TiC-Ti-Al and TiB₂-Ti-Al coatings on the surface of 5CrNiMo die steel. The microhardness of the formed coatings depends on which part of the structure is measured. The microhardness differs by more than 12 times in the matrix material and in the inclusions of titanium carbides and borides. However, the combination of metal matrix composites and the reinforcing inclusions suggests a high complex of properties of the formed coatings. The formation of wear-resistant coatings of these systems is carried out by two-stage treatment. At the first stage, electro-explosive spraying of TiC-Ti-Al or TiB₂-Ti-Al coatings is performed. At the second stage, electron-beam treatment of these coatings is carried out. The structure uniformity during electro-explosive spraying is enforced by specially designed composite conductors, which are electrically exploded. The reason for wear resistance increase is the formation of a multiphase finely dispersed structure in coatings based on TiC, Al₃Ti, Ti and Ti₃Al phases for TiC-Ti-Al system and TiB₂, TiB and AlTi₃ phases for TiB₂-Ti-Al system. The structure was also studied in detail at the interface between the coatings and the substrate using transmission electron microscopy. The studies of the structure of electro-explosive coatings were compared with the structural features of TiC-Ti-Al composite coatings obtained by the laser cladding technique on the surface of TiAl alloy. Comparison of the findings of the structure obtained by these two different spraying methods revealed both general patterns and characteristic features for each of the coating methods. They relate to features at the interface between the coatings and the substrate, as well as characteristic unitary coating layers.