Preparation of Metal–Ceramic Coatings by Microplasma Spraying of Mechanochemically Synthesized Ti/HfB₂ Composite Powders

This paper reports on the use of titanium/hafnium diboride composite powders for producing metal–ceramic coatings. The composite powders were prepared by high-energy mechanochemical synthesis. The starting components used were PTOM-1 titanium powder (as a matrix powder) and hafnium diboride powder (as a reinforcing agent). The composite powders were characterized by microstructural analysis and their particle size composition was determined. Examination of their morphology showed that the number of hafnium diboride particles embedded in the surface layer of the titanium particles increased with increasing reinforcing agent content in the mixture for mechanochemical synthesis. Assessment of the particle size composition of the powders showed that the size range 10–60 μm accounted for the largest volume fraction of the particles: from 7 to 10%. The microhardness of the coatings produced by microplasma spraying was determined using their transverse polished microsections. Scanning electron microscopy images showed that increasing the percentage of hafnium diboride in the starting mixtures increased the amount of HfB₂ in the coatings. In all of the polished microsections examined, the coating was firmly adherent to the substrate material, without through pores. As the hafnium diboride content was raised from 10 to 60 wt %, the microhardness of the coatings increased in proportion to it. The composite powder containing 60 wt % hafnium diboride had the highest microhardness: 1076 HV.