Technological aspects of improving adhesion of TiNiZr coating materials with thermoelastic phase transformations formed by high-velocity oxygen-fuel spraying

Abstract

The authors discuss technological aspects of increasing the adhesion of coatings made of materials with thermoelastic phase TiNiZr transformations formed by high-velocity oxygen-fuel spraying (HVOF) with a steel base by means of using a combined method, including HVOF and electromechanical treatment (EMT). The authors presented the results of the structure and elemental composition of the surface-modified layer before and after high-frequency impulse action in the EMT process and established new possibilities of modification of the structure and properties. It is shown that in the optimal modes of EMT, the fusion zone of the coating and the base is 10-20 microns. The authors designed the statistical models of technological process, which allowed defining fusion depth and diameter of a contact core depending on technological modes of EMT, as well as a current density and frequency or pulse duration. Adhesion tests according to State Standard 98844-99 showed that the strength of the coating with the base reaches (0.3-0.4) from the tensile strength of the base, depending on the depth and size of the fusion zone. It is recommended to perform additional thermomechanical processing to ensure the functional properties of materials with shape memory effect in the TiNiZr surface layer.