Spraying wear-resistant coatings from clad powders TiB2/Ti and HfB2/Ti

Abstract

The present work considers the results on synthesis of composite clad powder systems with the “core-shell” type of structure for spraying wear-resistant metal-ceramic coatings. Powders of highly hard TiB2 and HfB2 borides were used as a core for the synthesis of a composite powder, and titanium was used to create coating on their surface. The cladding layer is synthesized by the iodine transport method. Powder cladding uses the method of detecting one component on another gas transport path, the agent of which is contact iodine. The deposition of composite clad powders of the TiB2 /Ti and HfB2 /Ti systems is implemented by the microplasma method, which, in contrast to the classical plasma deposition, makes it possible to dissolve transformations in composite powders due to thermal action. In the study of transverse microsections of sprayed coatings, it was found that during microplasma spraying, titanium is saturated with oxygen, forming a titanium dioxide phase, as a result of which the clad composite powder of systems TiB2 /Ti and HfB2 /Ti are converted into coatings from systems TiB2 (TiB)/Ti(TiO2 ) and HfB2 /Ti(TiO2 ). Features of the composition in terms of coating thickness were revealed. The study of hardness shows that the integral value of microhardness for a coating based on titanium diboride is 1300 HV. Coating based on hafnium diboride has integral microhardness of about 1600 HV. When checking the wear resistance, pairs with TiB2 (TiB)/Ti(TiO2 ) and HfB2 /Ti(TiO2 ) coatings were mated with a counterbody from the 45Kh sample without coatings and together with each other. Despite the lower microhardness, the most wear-resistant is coating of TiB2 (TiB)/Ti(TiO2 ) system.