Low Pressure Carbonitriding – heat treatment suited for a sustainable future

Chwiałkowski Łukasz - SECO/WARWICK S.A. (Poland)

Atmosphere carbonitriding in batch and/or continuous furnaces has been historically used for low carbon and low alloy steels, mainly to improve wear resistance of the treated parts. Whereas the results of this process are very beneficial, the traditional way of performing carbonitriding (in flammable and highly explosive endothermic atmosphere) is not up to date with expectations, and soon strict governmental regulations, concerning sustainability and reduction of carbon footprint. Alternatively carbonitriding can be performed utilizing safe, proven, reliable and modern low-pressure technology in vacuum furnaces. To support heat treaters in preparations for the inevitable industrial transformation SECO/WARWICK have investigated low pressure carbonitriding technology in vacuum furnaces.
Multiple different low pressure carburizing and low pressure carbonitriding test processes were performed on a variety of steel grades. Aim of the test processes was to assess the differences in metallographic results (microhardness and microstructure) of the samples under different process conditions. As a result an optimal low pressure carbonitriding recipe has been defined and carried out. The test samples from the process were further examined in a tribological test for abrasion resistance in laboratory conditions. Overall results have clearly indicated that for certain steel grades low pressure carbonitriding improves hardenability, microhardness, microstructure and abrasion resistance.
Research has proven that modern vacuum furnaces with low pressure carbonitriding technology can be considered as a viable and environmentally friendly alternative to atmosphere furnaces with traditional carbonitriding.

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