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- Title
Enhanced Nitriding of 38CrMoAl Steels with Laser Vibrational Excitation of Ammonia.
- Authors
Fan, Lisha; Lv, Yifeng; Wu, Ling; Zhang, Shuowen; Wang, Tingbin; Liu, Fan; Ding, Xiaoyu; Yao, Jianhua
- Abstract
Gas nitriding is a thermochemical surface hardening process that is widely used in industry but suffers from a low decomposition rate of ammonia (NH3) and extremely long processing cycles. To enhance the gas nitriding efficiency, laser vibrational excitation of NH3 is introduced into the gas nitriding of 38CrMoAl steels. By matching the laser wavelength with the N–H wagging mode of NH3, laser energy can be preferentially deposited into NH3 molecules and facilitates their dissociation. The morphology, composition, and mechanical properties of nitrided 38CrMoAl plates strongly depend on the nitriding time length. Nitrided surfaces experience phase transition from α-Fe solid solution with N through γ′-Fe4N to ε-Fe2~3N phase as prolonging the nitriding time length. A 38CrMoAl plate nitrided with laser vibrational excitation of NH3 for 6 hours possesses a higher nitrogen content (7.1 wt pct) and a harder surface (944 HV0.1) than that nitrided without laser (6.3 wt pct, and 811 HV0.1). The study concludes that laser vibrational excitation of NH3 is an effective way to promote nitrogen diffusion kinetics and shorten the nitriding cycle of gas nitriding, which holds great promise in the development of gas nitriding.
- Subjects
SURFACE hardening; PHASE transitions; DIFFUSION kinetics; SOLID solutions; LASERS
- Publication
Metallurgical & Materials Transactions. Part A, 2024, Vol 55, Issue 9, p3302
- ISSN
1073-5623
- Publication type
Article
- DOI
10.1007/s11661-024-07456-y