The effect of boronizing medium on the properties of borided AISI 316L stainless steel

Abstract

In this study, we investigated the effect of bronzing medium on the properties of borided AISI 316L austenitic surgical stainless steel. Boronizing was carried out on a cylindrical bar of AISI 316L austenitic surgical stainless steel with a diameter of 2 mm and a length of 10 mm using slurry salt bath consisting of borax, boric acid and ferro-silicon and solid boronizing media consisting of Ekabor powders. Boronizing treatments were conducted at 850 degreesC, 900 degreesC, 950 degreesC, and 1000 degreesC, for 2, 4 and 6 hrs. respectively. The presence of borides (e.g. Fe2B, CrB, Ni3B) formed on the surface of borided AISI 316L stainless steel was confirmed by classical metallographic technique combined with x-ray diffraction (XRD) analysis. In solid boronizing method, boronizing performed at 1000 degreesC for 4-6 h results in spalling and/or removing of coating layer. Whereas, this type of failure does not occur during boronizing in slurry salt bath at 1000 degreesC for the same length of time. However, it was found that solid boronizing; method increases thickness of boride layer compared with slurry salt bath boronizing method under same conditions. Therefore, it is possible to claim that the slurry salt bath boronizing method is superior to solid boronizing method at elevated temperatures. The distribution of alloying elements from surface to interior was determined by means of energy dispersive x-ray spectroscopy (EDS).