The Microstructure and Properties of Ni-Si-La2O3 Coatings Deposited on 304 Stainless Steel by Microwave Cladding

Abstract

In this investigation, microwave radiation was used alongside a combination of Ni powder, Si powder, and La2O3 (Lanthanum oxide) powder to create surface cladding on SS-304 steel. To complete the microwave cladding process, 900 W at 2.45 GHz was used for 120 s. “Response surface methodology (RSM)” was utilized to attain the optimal combination of microwave cladding process parameters. The surface hardness of the cladding samples was taken as a response. The optimal combination of microwave cladding process parameters was found to be Si (wt.%) of 19.28, a skin depth of 4.57 µm, irradiation time of 118 s, and La2O3 (wt.%) of 11 to achieve a surface hardness of 287.25 HV. Experimental surface hardness at the corresponding microwave-cladding-process parameters was found to be 279 HV. The hardness of SS-304 was improved by about 32.85% at the optimum combination of microwave cladding process parameters. The SEM and optical microscopic images showed the presence of Si, Ni, and La2O3 particles. SEM images of the “cladding layer and surface” showed the “uniform cladding layer” with “fewer dark pixels” (yielding higher homogeneity). Higher homogeneity reduced the dimensional deviation in the developed cladding surface. XRD of the cladded surface showed the presence of FeNi, Ni2Si, FeNi3, NiSi2, Ni3C, NiC, and La2O3 phases. The “wear rate and coefficient of friction” of the developed cladded surface with 69.72% Ni, 19.28% Si, and 11% La2O3 particles were found to be 0.00367 mm3/m and 0.312, respectively. “Few dark spots” were observed on the “corroded surface”. These “dark spots” displayed “some corrosion (corrosion weight loss 0.49 mg)” in a “3.5 wt.% NaCl environment”.