Effect of decarbonized layer on plasma nitriding of 38CrMoAl steel

doi:10.13251/j.issn.0254-6051.2020.10.038

Abstract

Abstract: Tower-like specimen of 38CrMoAl steel with different thickness decarbonized layer was plasma nitrided. Infiltration rate, surface hardness and microstructure of the specimen before and after nitriding was studied by microhardness tester, OM and SEM. The results show that the widmannstatten structure is found in residual decarbonized layer and gradually increases with increase of the decarbonized layer. The speed of plasma nitriding increases first and then decreases with the increase of decarbonized layer thickness. The diffusion expressway of nitrogen-atoms and formation of nitride is provided by ferrite in widmannstatten structure. There are many fishbone, net and nervation nitrides on the surface of diffusion layer and it exhibits increase tendency with the increase of number and depth of decarbonized layer. Although the residual decarburized layer on the surface of the 38CrMoAl steel can accelerate the penetration rate, it will increase the bad structure of the carburized layer and increase the risk of exfoliation. Therefore, the machining allowance of the 38CrMoAl steel workpieces should be appropriately increased.

Key words: 38CrMoAl steel, plasma nitriding, decarbonized layer, diffusion dynamics

CLC Number:

TG156

Wang Yanfang, Yin Tingfeng, Li Shuangxi. Effect of decarbonized layer on plasma nitriding of 38CrMoAl steel[J]. Heat Treatment of Metals, 2020, 45(10): 194-198.

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