Wear improvement of sol–gel silica coatings on A380/SiCp aluminium composite substrate by diode laser sintering

In this investigation, a high power diode laser (HPDL) was used to induce the microstructural refinement on the surface of a SiC particulate (SiCp) reinforced Al-based metal matrix composite (A380/SiC/20p) and, at the same time, to the sintering of a sol–gel ceramic layer deposited on the surface of the mentioned substrate. The purely inorganic silica ceramic coating was synthesised through the organic sol–gel route, using tetraethoxysilane (TEOS) as alkoxide precursor and the dip-coating as the deposition technique on the surface of the A380/SiC/20p composite. Optimisation of the laser parameters led to homogeneous and free of cracking coatings and also to the refinement of the surface microstructure of the substrate by means of the dissolution of the intermetallic precipitates, the decrease in the aluminium dendrites size and a better distribution of the silicon carbide particles. Unlubricated pin-on-disc wear tests confirmed the increase (89% in terms of specific wear rate drop) in the wear resistance of the coated substrates treated by the HPDL.

► HPDL is a cost-saving technique for sintering of sol–gel silica coatings. ► Optimisation of laser parameters allowed the microstructure refinement. ► The top layer increased its hardness up to105% by using higher input energy. ► Silica coating reduced the specific wear rate of the composite.