Mechanical tools

. state the process of case hardening by gas nitriding . state the process of case hardening by nitriding in a salt bath In the nitriding process, the surface is enriched not with carbon, but with nitrogen. There are two systems in common use, gas nitriding and salt bath nitriding. Gas nitriding The gas nitriding process consists of heating the parts at 500°c in a constant circulation of ammonia gas for up to 100 hours. During the gas nitriding process, the parts are in an externally heated gas tight box, fitted with inlet and outlet bores for the ammonia gas which supplies the nitrogen. At the completion of the soaking the ammonia is still circulated untill the temparature of the steel has fallen to about 150°c, when the box is opened, and the cooling completed in air. Nitriding causes a film to be produced on the surface but this can be removed by a light buffing. Nitriding in salt bath Special nitriding baths are used for salt bath nitriding. This process is suitable for all alloyed...