Saturation of stainless and structural steels with hydrogen during nitriding

Autor: Cherkis, Yu. Yu., Krutogina, N. A., Savinkov, R. A.
Zdroj: Metal Science and Heat Treatment; March 1981, Vol. 23 Issue: 3 p165-171, 7p
Abstrakt: 1.In the process of gas nitriding, all the stainless and structural steels tested are saturated with hydrogen; the concentration of diffusionally mobile hydrogen in samples 8 mm in diameter and 20 mm long varies from 5×106 to 20×10-6 m3/100 g of metal. Most of the hydrogen is concentrated in a thin surface layer (~0.05 mm) and amounts to 350×10-6 m3/100 g of metal, compared with (20–40)×10-6 m3/100 g of metal in the remainder of the case; hydrogen does not diffuse into the core.2.Tempering for 10 h in a vacuum furnace or in dissociated ammonia not containing atomic hydrogen leads to a reduction of the hydrogen concentration in the case by a factor larger than 10, an increase in the corrosion resistance of nitrided stainless steels, and lower brittleness of the nitrided case.3.Diffusionally mobile hydrogen has no effect on the mechanical properties of nitrided samples: The reduction in cross-sectional area and susceptibility to delayed fracture under constant static load remain unchanged in tests of samples with a sharp notch (r=0.1 mm).4.The reduction of the hydrogen concentration leads to formation of a high-quality passive film on the surface of the sample, which improves the corrosion resistance of the steels.
Databáze: Supplemental Index
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