Effect of rare earth elements on plasma nitriding kinetics of 2205 duplex stainless steel at 500℃
A comparative study was conducted to examine the plasma nitriding kinetics of 2205 duplex stainless steel in NH3 with and without rare earths at 500℃(8,16,24 h).The effective hardening layer(78.3 μm),compound layer(58.3 μm),and diffusion layer(20.0 μm)thickening rates at 8 hours of nitriding with rare earths(La)were all the highest,33.8%,17.8%,and 122.2%,respectively.The maximum surface hardness of the specimen after 24 hours of nitriding is 1 866.7 HV0.025,and the maximum hardness of the nitrided layer is 1 782 HV0.025,which is 4.9 times of the core hardness(365 HV0.025).The γ'-Fe4N diffraction peak becomes higher and stronger after plasma nitriding with rare earth,and the addition of rare earths reduces the precipitation of ε-Fe2-3N phase.The diffusion coefficient K increased by 22.8%to 1.51×10-13 m2·s-1 with the addition of rare earths compared to plasma nitriding without rare earth.
2205 duplex stainless steelplasma nitriding with rare earthmicrostructurekinetics
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