Nitriding of low-carbon stainless steels

Conclusions

• 1. The maximum case hardness is attained in brief nitriding of steels 000Kh18 and 000Kh18N9. An increase of nitriding time leads to a lower case hardness to a value depending on the temperature, after which it remains almost constant.

• 2. The case hardness varies with the dispersity of the nitrides, and the maximum hardness is attained when the nitrides are in the preprecipitation stage, ensuring the largest distortion of the matrix lattice.

• 3. Brief nitriding of low-carbon stainless steels makes it possible to obtain an even high-quality case with a higher hardness than after prolonged nitriding.

• 4. Cold treatment of nitrided steel 000Kh18 increases the case hardness due to precipitation (preprecipitation) of CrN.

• 5. High-temperature heating with quenching and tempering at 500° of nitrided steel 000Kh18N9 increases the case hardness due to the precipitation or preprecipitation of dispersed nitrides with decomposition of γ phase to α phase and CrN by the intermediate mechanism.

• 6. The case hardness reaches the desired value not only with nitriding but also in the process of cooling, and varies with the dispersity of the nitrides formed.