Effect of chromic acid anodization on the corrosion resistance of laser cladding austenitic stainless steel coatings based on orthogonal tests

In this paper, Ni transition layer and Fe-based alloy coatings were prepared on HT250 by laser cladding technology, and the corrosion resistance of the coatings was further enhanced by the chromic acid anodization (CAA) surface treatment process. The effects of time (t), current intensity (I), and temperature (T) on the microstructure and corrosion resistance of the coating after CAA were explored based on the three-factor and three-level orthogonal test method. The results show that after CAA, the intergranular morphology of the coating is corroded, the intragranular organization is exposed and protrudes, and the micro-morphology shows a multilayer "skeleton" overlapping structure. The main phases were transformed from gamma-Fe (FCC) to CrNi (FCC) and FeNi (BCC). The corrosion residue of the original coating is a lamellar metal-carbide weave, whereas the CAA coating is fibrous. The order of influence of CAA process parameters on corrosion depth and maximum impedance value is I > t > T. Ion the degree of densification of the passivated film is 1.03 and 1.81 times higher than T and t, respectively. The best corrosion resistance of the sample was obtained at t = 30 min, I = 0.1 A, and T = 40 degree celsius, and its corrosion rate (2.83 x 10-3 g/m(2)& sdot;h) was 29.88 % lower than the original coating (4.03 x 10-3 g/m(2)h)