Gradient microstructure and microhardness in a nitrided 18CrNiMo7-6 gear steel: Paper

R. Yang, G. L. Wu, X. Zhang, W. T. Fu, X. Huang

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A commercial gear steel (18CrNiMo7-6) containing a tempered martensite structure was nitrided using a pressurized gas nitriding process under a pressure of 5 atm at 530 °C for 5 hours. The mechanical properties and microstructure of the nitrided sample were characterized by Vickers hardness measurements, X-ray diffraction, and backscatter electron imaging in a scanning electron microscope. A micro-hardness gradient was identified over a distance of 500 μm with hardness values of 900 HV at the top surface and 300 HV in the core. This micro-hardness gradient corresponds to a gradient in the microstructure that changes from a nitride compound layer at the top surface (∼ 20 μm thick) to a diffusion zone with a decreasing nitrogen concentration and precipitate density with distance from the surface, finally reaching the core matrix layer with a recovered martensite structure.
Original languageEnglish
Article number012047
JournalI O P Conference Series: Materials Science and Engineering
Issue number1
Publication statusPublished - 2017
Event38th Risø International Symposium on Materials Science - Technical University of Denmark , Roskilde, Denmark
Duration: 4 Sep 20178 Sep 2017


Conference38th Risø International Symposium on Materials Science
LocationTechnical University of Denmark

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