Carbonitriding is a gaseous process for the simultaneous diffusion of carbon and nitrogen into steel and consists of subjecting steel parts to the action of a carburizing gas to which is added a nitriding gas, usually anhydrous ammonia. Carbonitriding is carried out over the range 800°C to 900°C with a preference for 850°C – 900°C. the duration of treatment for a given case depth is a function largely of temperature, provided that a suitable gaseous atmosphere is employed. Furnaces used for carbonitriding are generally of continuous type such as shaker hearth furnace, rotary drum furnace since the work is nearly always directly quenched in oil from the carbonitriding atmosphere. Batch type furnaces of the standard type used for gas carburizing may also be employed, particularly where the parts in question are not suitable for rotary drum or shaker hearth furnaces.
Carbonitriding is an ideal process for the hardening of small components, where great resistance to wear is required and generally operating where the case depth does not exceed 0.025” – 0.030”
Advantages of carbonitriding
- The process is safe, clean and simple to operate – no salts to handle no washing off, and the process can be operated by unskilled labour.
- The process is applicable to mass production methods
- Reduced distortion due to the lower temperature required for carbonitriding as compared with carburizing, distortion is reduced.
- Improved hardenability is obtained using plain carbon steels instead of alloy steels, doe to the introduction of nitrogen into the case.