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1 2009

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Badania naprężeń własnych w strefach azotków żelaza warstw azotowanych na stalach 38HMJ i WCL

Pachutko B. B., Małdziński L. L.

Obróbka Plastyczna Metali

2009

T. 20, nr 2

49-61

The paper presents the results of stress measurements performed by the sin2? x-ray method in nitrided layers of 38HMJ and WCL steels. The measurements have been carried out on steels whose structure and microhardness distribution had been assessed during previously performed works. Those works concerned steels with a two-zone layer of nitrides, ?+?', and a precipitation zone, ?, under the nitride zone. Additional investigation has been performed, too, on steels which had been gas nitrided at the temperature of 550 oC and nitrogen potential, Np = 1 atm-0.5 in order to obtain a one-phase layer of iron nitrides. Investigation of ?? stresses in both steels have shown that, in phase ? of zone ?+?', the stresses changed from compression stresses with maximum value of about -200 MPa to maximum tensile ones of about 220 MPa when the time of nitriding was increased from 2 hours to about 50 hours for the processes performed under the conditions of 550 oC and Np = 4 atm-0.5 also 500 C and Np = 14 atm-0,5. In the one-phase zone, ?', of the WCL steel compression stresses have been found to increase from about -120 MPa to -760 MPa when the time of nitriding was extended from 16 hours to 43 hours under the conditions of 550 oC and Np = 1 atm-0.5. In the layer compounds being a mixture of phases ? and ?' of the 38HMJ steel, compression stresses have also been obtained; the larger of those amounting over -900 MPa where found in phase ?' after the longest nitriding time under the same conditions.