In-Situ TiB2–TiC–Al2O3Composite Coating on Aluminum by Laser Surface Modification

To improve the surface hardness of aluminum, in-situ TiB2–TiC–Al2O3 composite coating was deposited on it by pre-placed laser coating process using precursor mixture of (TiO2 + B4C) and (TiO2 + B4C + Al). Pulsed Nd:YAG laser was used to produce coating track by scanning a laser beam in overlapped condition. Multiple tracks again overlapped to get a wider coating area. Phase constituents and microstructure of the deposited coating were studied by XRD and FESEM analysis. Vickers micro-hardness tester was used to measure micro-hardness of the coating. Results indicate that, in appropriate laser processing condition, coating was obtained with metallurgical bonding to aluminum substrate. XRD and microstructure analysis confirms the formation of TiB2, TiC, and Al2O3 in the coating layer through in-situ reaction of reactant powders. Micro-hardness of the coating was found appreciably higher in comparison to the as-received aluminum substrate, due to presence of hard ceramic particles produced during in-situ reaction and their grain refinement for rapid cooling.