Surface Modification of Materials
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 HV0.1 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 HV0.1 900 kg/mm2. Radiometal also boronized easily with a layer hardness of HV0.1 850 kg/mm2. Wear resistance trials are still in progress.
KeywordsMedium Carbon Steel Plain Carbon Steel Boride Layer Iron Boride Nickel Boride
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