IMPROVEMENT OF HOT CORROSION RESISTANCE OF AUSTENITIC STAINLESS STEEL 316L IN ASH BY CHROMIZING-SILICONIZING

Abstract

The simultaneous deposition of Cr and Si into austenitic stainless steel 316L alloy using a halide-activated pack-cementation process is described, using a pack mixture containing (67 wt. % Cr, 8 wt. % Si, 2 wt. % NH4Cl, 23 wt. % Al2O3). The diffusion coating process is carried out at 950oC for 6hrs under Ar atmosphere. It was found that diffusion coating time produce coating thickness of 80-100µm, the corrosion resistant properties of austenitic stainless steel can be improved by enriching the surface composition in Cr and Si using pack cementation process, this study compare the hot corrosion performance of uncoated and coated austenitic stainless steel 316L with chromized-siliconized diffusion coating specimens in the presence of molten mixture of Na2So4and V2O5at 850oC and compare the micro-hardness between them. In the case of coated austenitic stainless steel 316L alloy with chromized-siliconized diffusion coating, specific weight gain will be observed while specific weight lose can be observed in the case of uncoated austenitic stainless steel 316L alloy. Diffusion coated austenitic stainless steel 316L alloy has shown excellent corrosion resistance and higher micro hardness than uncoated austenitic stainless steel 316L alloy because the coated layer that consisted mainly of CrSi2 and Cr3Si phases.