ABRASIVE WEAR OF BORON-ADDED HIGH-CHROMIUM

The effect of small amounts of boron (0.2%B) added to a 17%Cr and to a 27%Cr white irons were studied. The experimental alloys were made in an induction furnace by using high-purity raw materials. Boron was added at the end of the ironmaking process just before pouring. Thin bars of 10 mm diameter were solidified into metallic moulds. The microstructure showed aligned eutectic carbides in the direction of the heat flow with a finer structure for the iron with the higher boron amount in both 17% and 27%Cr irons. The alloys were then heat treated at 950C to destabilize the austenitic matrix; a stronger mainly martensitic matrix reinforced with secondary carbides resulted from such treatment. The as-cast and ?heat treated alloys were tested under abrasive wear by using a rounded abrasive stone as a counterface and using five different loads (from 52 to 154 Newtons). Wear resistance resulted higher for: (i) the heat treated irons since the martensitic matrix reinforced with secondary carbides better supported the eutectic carbide phase against fracture, (ii) the boron added irons due to the finer structure, and (iii) the irons whose chromium content was higher. The results are discussed in terms of the effect of boron and chromium content.