Herein, phase formation and sintering of hafnium carbonitride ceramics from a 4HfC-3HfN powder mixture using reactive spark plasma sintering are studied. X-ray diffraction (XRD) data show that the mutual heterodiffusion of carbon C and nitrogen N increases with sintering temperature within the studied temperature range 1500-2100 C. 4HfC-3HfN powder sintering at 1900 C for 5 min under 60 MPa pressure yields HfC x N 1Àx solid solution ceramics. The ceramic sample prepared under optimal conditions (2100 C, 5 min, 60 MPa) is characterized by an average grain size of 10 μm, microhardness of 19.6-22.5 GPa, and relative density above %97%.
Titanium-based alloys are widely used in aerospace engineering. They have good mechanical and corrosion properties but, in some cases, the material itself or the coating should meet some additional requirements. For example, it may be a requirement of high reflectance to provide effective temperature control. Wollastonite is a promising component for reflective coatings because it improves both their whiteness and mechanical properties. This paper presents the results of studying the composition, the structure and the adhesive strength of wollastonite-containing silicate coatings to titanium substrate. The surface of titanium samples was pre-treated by laser cladding with TiC and etching to provide surface porosity. It has been shown that such treatment allows a significantly increase in the adhesive strength of the coating to the substrate. A decrease in the adhesive strength was observed on titanium samples with an excess of TiO2 on the surface. This is caused by the formation of crystalline PbTiO3 at the interface.
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