Laser-induced deposition of sol–gel alumina coating on stainless steel under wet condition

Excimer laser (KrF gas with wavelength 248 nm) was used to deposit alumina coating onto stainless steel substrates through a sol–gel route. Sol–gel alumina coating was first applied on the substrate surface and then immediately irradiated with the excimer laser to initiate the deposition of alumina from the sol onto the substrate surface. The composition and microstructure of alumina coatings obtained through laser-induced deposition were characterised using ATR-FTIR, XRD, SEM, optical microscopy and the mechanical properties were measured by means of nano-indentation. Results show that the laser induced deposition leads to formation of alumina coating which is partially crystallised in γ-form. The deposited coatings demonstrate significantly different composition and microstructure in comparison with the as-dried coating from the same sol–gel alumina. Nano-indentation measurements prove that the laser-deposited alumina coating has much higher mechanical strength than the as-dried xerogel coating, with the hardness values four times and reduced modulus 10 times higher than those of the latter, respectively.