Diffusion Nitride Coatings for Heat-Resistant Steels

Abstract

The effect of ion nitriding and nitriding in a melamine-based powder mixture on the structure and properties of AISI A290C1M steel was studied in the paper. Using ion nitriding made it possible to shorten the technological cycle’s duration by 5–6 times compared to two-stage nitriding, optimize the diffusion layer’s composition, provide a technologically simple process automation scheme, and improve the quality of nitride coatings. After the proposed mode of ion nitriding, a saturated layer depth of 0.25–0.32 mm, hardness up to 1000 HV, and an increase in wear resistance by 2.17 times were obtained. Using 95% melamine + 5% sodium fluoride during nitriding in a powder mixture significantly simplified the technological process. It did not require additional expensive equipment, which in turn significantly simplified the nitriding process with energy savings. The proposed technology and the composition of the mixture contributed to a significant acceleration of the nitriding process of AISI A290C1M steel, compared to traditional gas nitriding, and to obtain a hardness of the nitride layer of 970 HV and an increase in wear resistance by 2.6 times. A nitriding speed is explained by a significantly higher amount of atomic nitrogen when using melamine instead of ammonia and by the almost simultaneous disintegration of nanodispersed particles when the nitriding temperature was reached. After nitriding in a powder mixture, steel was subject to the slightest wear.