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The Influence of Plasma Nitriding Process on Mechanical Properties of 14NiCr14 Steel

The article deals with an alteration of mechanical properties of plasma nitrided steel. Experimental work was focused on evaluation of influence of plasma nitriding process on the notch toughness of steel. Experiments were realized on V-notch samples of size 10x10x55 mm (according to ISO 148-1 standard) from 14NiCr14 steel. The 14NiCr14 steel was heat treated prior plasma nitriding. The heat treatment consisted of hardening at 850 °C and tempering on elimination of internal stress at 200 °C. Heat treated experimental samples were plasma nitrided at 450 °C, 500 °C and 550 °C. The notch toughness tests of steel were carried out using the instrumental Charpy hammer at test temperatures-40 °C, +21 °C and +70 °C. The notch toughness of plasma nitrided samples achieved nearly identical values as heat treated samples thus plasma nitriding did not reduce the values of notch toughness. The increase in temperature of the plasma nitriding process even led to achievement of higher values of notch toughness compared with heat treatment specimens namely at all test temperatures.