INVESTIGATION OF EFFICIENCY OF COMPLEX ION NITRIDING FOR STEEL MODIFICATION
Journal Title: Вестник Харьковского национального автомобильно-дорожного университета - Year 2018, Vol 82, Issue
Abstract
Problem. The development of integrated ion nitrid-ing technology is actual for industrial production. This method is in the development stage, especially for steels that are not classical for nitriding, for ex-ample, cheap and available steel 9XC for produc-tion. The goal of the research is to study the influ-ence parameters of the process of low-temperature nitriding in plasma of a non-independent low-pressure arc discharge on structure and properties of the surface and near-surface layers of punches from steel 9XC in combination with subsequent heat treatment. Results. The research solved the follow-ing tasks: 1. A metallographic analysis of 9XС steel samples after complex ion nitriding is carried out, which includes nitriding and subsequent heat treat-ment (quenching and tempering at various tempera-tures). 2. Measured microhardness of surface and near-surface layers in depth. 3. Phase analysis is done. 4. Determined depths of nitrogen-hardened layers and their morphological features. 5. Conclu-sions are made on the practical use of integrated ion nitriding technology. Practical value. For harden-ing punches of steel 9XC method of complex processing are proposed and tested in the work. It in-cludes nitriding in a vacuum gas discharge before quenching and tempering. At the same time, the process of diffusion of nitrogen atoms is significantly accelerated (since nitrogen atoms more easily penetrate non-hardened steel), which leads to an in-crease in the depth to the penetration of nitrogen atoms and a change in structure and hardness. It was established that, by properties, the impact area is divided into a surface layer (with a thickness of about 200 μm) with a lower hardness and a deeper working layer with a higher hardness. The size of the strengthening zone is 560–920 μm. At the same time, increased hardness compared to the main structure without nitriding is remained at a depth exceeding 2000 μm. The surface layer of parts with low hardness must be mechanically processed to obtain the required dimensional accuracy and roughness. The surface hardness of the punches made of steel 9XC after such treatment is at the level of 6600 MPa. The phase composition of the nitrated layer with high hardness consists of the lower nitride of Fe4N and a solution of nitrogen in α-Fe. The results obtained are relevant for steel with a low tempering temperature.
Authors and Affiliations
O. V. Sоbоl, S. M. Shevchenko, T. O. Рrotasenko
Keywords
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- EP ID EP473773
- DOI 10.30977/BUL.2219-5548.2018.82.0.13
- Views 73
- Downloads 0
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