Surface Modification of Materials

Summary

The boronizing of steels, nickel and radiometal by the pack method was carried out in a muffle furnace at temperatures between 800 and 1000°C to determine if the hard layer formed met the criterion of wear resistance for conical self-acting gas bearings produced by Ferranti PLC. On steels, an Fe₂B layer of HV_0.1 1500 kg/mm² was formed, usually with some (unwanted) FeB on the outer surface. This was easily removed by a vacuum anneal, again at temperatures between 800 and 1000°C, and, if carried out on a suitable low-alloy steel, a gas quench after the anneal allowed development of the core properties without affecting either the surface hardness or adhesion. Nickel boronized in a similar manner resulted in a predominantly Ni₃B layer three times thicker than that developed on plain carbon steel under identical boronizing conditions and with a hardness of HV_0.1 900 kg/mm². Radiometal also boronized easily with a layer hardness of HV_0.1 850 kg/mm². Wear resistance trials are still in progress.