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Hot dip aluminizing of 316l stainless steel on aluminuim and aluminuim-silicon alloys

A.A.Omar, M.M.Al-Aiat, S.I.Abdel-Aziz

316L stainless steel was coated by hot-dipping into commercially pure Al and twoAl-Si alloys of 7%Si and 11.5%Si contents at dipping time varying from 1 to 60 min and temperatures ranging from 750 to 900ºC. Moreover, 5%Fe was added to each bath at 900ï‚°C. Microstructure observation, morphology of the alloy layer, element distribution, chemical composition and microhardness determination were performed by optical microscopy, scanning electron microscope (SEM) with an energy dispersive X-ray facility (EDX), and microhardness tester. The thickness of the intermetallic layer formed increases with increasing both the bath temperature and dipping time. Based on the experimental data, it is found that the largest and most uniform layer thickness was obtained at 800ºC and time 20 min in pure Al molten bath, and this is also the case when aluminizing inAl-11.5%Simolten bath, but when using Al-7%Si molten bath, the optimum dipping temperature was about 750ï‚°C also at time 20 min. The existence of Si reduces the intermetallic layer thickness and increases its microhardness. The addition of 5%Fe to the melt increases the layer thickness.