Effect of chromium addition on the microstructure and mechanical properties of laser cladding Ti-Al-SiC composite coatings.

Chromium (Cr) critically enhances interfacial compatibility and mechanical properties of titanium (Ti) -based coatings, however, the specific effects of Cr content on microstructural evolution remain underexplored. In this study, Ti-Al-SiC-Crx (x = 0, 5, 10, 15) coatings were fabricated on Ti-6Al-4V (TC4) titanium alloy via laser cladding. The phase composition of the coating/annealed TC4 was determined by X-ray diffraction (XRD). The microstructure was observed using scanning electron microscopy (SEM), and the grain orientation was analyzed by electron backscatter diffraction (EBSD) attached to the SEM. The effects of Cr content on the microstructural evolution and grain characteristics of the coatings were investigated, and the resultant variations in mechanical properties were further analyzed. Results indicate that increasing Cr content promotes Ti4Cr/Cr2AlC precipitation, reduces Ti8C5 and increases Ti5Si3. Notably, the orientation strength of Ti5Si3 is enhanced, and the grain size of the coating is refined. Both the TC4 substrate and the laser-cladding coatings exhibit strain rate strengthening behavior. Crucially, yield strength, peak stress, and microhardness positively correlate with Cr content. At identical indentation depth, maximum load, indentation hardness, and Young's modulus progressively increase with Cr content, exceeding TC4 substrate values. Although friction coefficients rise with Cr content, the coating with 5 wt% Cr (Cr5) demonstrates minimal wear weight loss. This study highlights the potential of laser cladding Ti-Al-SiC-Crx coatings for aerospace applications, offering a unique combination of refined microstructure and superior mechanical performance.