Micro-structural, physical and tribological properties of HVOF spayed (TiC + Cr2O3) composite coatings

Abstract

Abstract Ceramic composite coatings of Titanium Carbide (TiC) and Chromium Oxide (Cr2O3) were applied on the surface of Al-6061, produced through High Velocity Oxy-Fuel (HVOF) technique. The combination of the coatings developed were TiC + 10%Cr2O3, were Cr2O3 acts as the reinforcement in TiC matrix and Cr2O3 + 10%TiC were TiC acts as the reinforcement in Cr2O3 matrix. The microstructural characterisation was conducted using the Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD). The SEM images showed better bonding of the TiC reinforcement to the Cr2O3 matrix and the XRD tests of the same showed the presence of of compounds of Chromium Oxide-Titanium Oxide in large quantities. The presence of these compounds indicates a clear bonding between the reinforcement and matrix of the coating. The physical properties of surface roughness and coating thickness were examined using the Surface Roughness Tester (SRT) and Coating Thickness Gauge (CTG) respectively. Coatings of Cr2O3 + 10%TiC were found to have consistent coating thickness and lower valleys and peaks. The Tribological wear evaluation was conducted using the Pin-on Disc wear tester according to the G99 ASTM standard. With the increasing axial load, it was observed that the wear reduced drastically for specimens coated with Cr2O3 + 10%TiC as compared to the specimens coated with TiC + 10%Cr2O3 and uncoated specimens. Thus, the micro-structural, physical and tribological properties analysed through the tests conducted showed that the combination of Cr2O3 + 10%TiC had superior properties in the tests conducted, as compared to TiC + 10%Cr2O3 coatings. This is mainly attributed to the adhesion abilities of the TiC reinforcement material to the Cr2O3 matrix of the ceramic composite coating. The research showed that the addition of Titanium Carbide reinforcement to the Chromium Oxide matrix in the coating enhanced the surface properties of Al-6061 to a large extent.