ガス窒化処理したクロム含有低合金鋼の拡散層硬さに及ぼす窒化温度と合金成分の影響

抄録

  Low alloy steels containing chromium, JIS-SCM435, DIN-31CrMoV9 and JIS-SACM645, were gas-nitrided at 773 K, 813 K and 853 K under several nitriding potentials, where the compound layer was generated at almost the beginning of the nitriding. Their hardness profiles and nitrogen distributions were characterized in the nitrogen diffusion layer. A linear relationship between the hardness increased, ΔHV, and nitrogen content in the diffusion layer was detected at each nitriding temperature in the steels. Their linear constants K were given by the Arrhenius type equation as a function of nitriding temperature in the steels. The hardness increased in the diffusion layer was demonstrated by the Orowan bypass mechanism for CrN platelets in DIN-31CrMoV9. The linear relationship in low alloy steels can be represented when the total volume fraction of precipitates such as CrN and AlN is less than several percent and their average particle size is less than 20 nm.