The present investigation focuses on the nitriding of medium carbon aluminium steel with a plasma transferred arc (PTA) torch. Nitrogen is used as the PTA plasma and/or shielding gas with a mixture of Argon with nitrogen. It is found that significant amount of nitrogen can be absorbed in the steel during the PTA melting process. The Nitrogen content increases from 0,005% wt. in the as received state to 0,18% wt. when 10% of the shielding and plasma gas is Nitrogen. The hardness of the steel is increased from 426 HV to 822 HV when using argon - nitrogen mixture instead of pure argon in the plasma and/or shielding gas of the PTA. The hardness increase is partially due to the formation of aluminium nitrides in the nitrided layer. The wear rate is decreased from 8,53×10{sup}(-3) to 1,4×10{sup}(-3) after the melt treatment mainly due to the increase in the hardness of the steel.
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