Microstructural stability of Ti-TiC satellites in aerosol cold-sprayed titanium coatings

Abstract

It has recently been proposed to modify titanium based cold-spray coatings with ceramic particles to improve their properties. One of the ideas to improve wear resistance is adding carbides into the coatings. This work describes the changes in microstructure and tribological properties induced by incorporating the Ti-TiC satellite into Ti coatings.

A powder mixture consisting of pure titanium and 20 wt% of Ti-TiC satellite powder was deposited along with pure titanium on an aluminum substrate using the Aerosol Cold Spray process. Scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) were employed for the microstructural characterization of deposited coatings. The sin²ψ method of XRD was also used to measure residual stresses in the coatings. The dry sliding tribological behavior of the coatings was evaluated via ball-on-disk tests against WC-Co counterbody. The experiments were conducted at room temperature, with a normal force of 10 N, a sliding distance of 100 m, and a sliding speed of 5 mm/s. The wear rates of the coatings and of the WC-Co counterparts were measured separately, and friction coefficients were recorded during each test.

Microstructural characterization using SEM and EBSD confirmed that in-situ formed TiC particles in the satellite powder, obtained through the CVD process, were embedded in the aerosol cold-sprayed coatings. The Ti-TiC satellite particles did not undergo significant changes during the spraying process compared to pure Ti powder. The presence of Ti-TiC satellites also resulted in an increase of microhardness, and dry sliding wear resistance. The absolute values of normal stresses along and perpendicularly to the torch movement direction decreased significantly when Ti-TiC satellite powder was added.