Structure and hardness of corrosion-resistant ferritic steels subjected to high-temperature nitriding

A comparative study of the effect of high-temperature internal nitriding (at above 1000°C) on the structure formation and hardening of thin-sheet samples of 08Kh17T (0.06% C-17.0% Cr-0.5% Ti) and 15Kh25T (0.10% C-25.0% Cr-0.5% Ti) steels was performed. The high-temperature internal nitriding of the 08Kh17T steel leads to the formation of martensite structure with Cr₂N precipitates. The nitriding of 15Kh25T steel results in the formation of a layered structure; in this case, individual layers consist of a mixture of the α and γ phases and Cr₂N particles, which are present in different proportions. It was shown that the internal nitriding of both steels with their subsequent annealing leads to their substantial uniform hardening.     

Increasing surface hardness of austenitic stainless steels by pack nitriding process

This paper investigated the possibility of increasing the surface hardness of austenitic stainless steels under very low nitrogen dissociation pressures of metal nitride powders using pack nitriding process. Thin sheet of 304 type of stainless steel of approximately 1 mm in thickness was used as a substrate for the study. Based on the results of thermochemical calculations, Cr₂N powder was selected as a nitrogen source from a series of metal nitride powders considered for the pack nitriding process, which included Si₃N₄, Mn₄N, BN, AlN and TiN. The pack nitriding was carried out in a sealed alumina retort at temperatures of 860 °C and 910 °C for up to 48 h. The surface was then characterised using techniques of SEM, XRD and microhardness testing. It was observed that the process used increased the surface hardness of the steel, but it also induced precipitation of chromium nitrides in the matrix even under the nitrogen dissociation pressures below 50 Pa. It was also observed that, in the nitrided layer, the γ phase of the steel was partially transformed to the α phase under the pack nitriding process conditions studied.     

新型渗氮钢的力学性能及渗氮特性

采用真空感应炉冶炼了低铝和无铝新型渗氮钢,研究了不同温度回火后钢的显微组织和力学性能.结果表明,在1000MPa强度级别下,试验钢的韧性明显高于常用的渗氮钢38CrMoAl.渗氮试验表明,在相同渗氮条件下,无铝试验钢渗层深度大、低铝渗氮钢的渗层硬度高,试验钢都具有较优良的综合渗氮性能.     

Enhancing the impact toughness of corrosion-resistant maraging steels

The article investigates the effect of the parameters of heat treatment on the grain structure of maraging steels. A regime of heat treatment is suggested that ensures sufficiently high impact toughness of these steels.Dnepropetrovsk State University. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 17–20, August, 1994.     

Delta-ferrite in hot-deformed metal of corrosion-resistant maraging steels

In some cases the -ferrite inherited from ingots is present in the hot-deformed metal of corrosion-resistant maraging steels. The residual -ferrite exerts a negative effect on the technological and operating characteristics of the metal. The present work presents results on transformations of -ferrite and variations of the properties of steels in quenching by different regimes. Recommendation on heat treatment of steels containing -ferrite are presented.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 36 – 39, July, 1995.     

Properties of and transformations in corrosion-resistant chrome-manganese steels

Corrosion-resistant high-strength steels, which are widely used in various branches of industry, contain large amounts of expensive and scarce alloying elements (Ni, Mo, etc.). To attain high strength, such steels require complex treatment including subzero treatment, plastic deformation, and aging, which also makes them more expensive. It is a topical problem to design economical materials and to devise technologies of enhancing their strength while economizing resources.Azov State Technical University (Mariupol). Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 28–32, February, 1994.     

High-temperature nitriding of chromium and chromium-nickel steels

Conclusions High-temperature nitriding accelerates the diffusion of nitrogen in steel. Nitriding at 700° for 3 h resulted in a case depth of 0.20–0.27 mm with HV 750–1000 for ferritic steels 0Kh13 and Kh16, and a case depth of 0.09 mm with HV 950 for austenitic steel Kh18N9T.Moscow Highway Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 19–22, February, 1971.     

Advantages in solution nitriding of stainless steels

Stainless steels are case-hardened with nitrogen instead of carbon to improve their resistance to pitting, wear, and cavitation. The new heat treatment is industrially available and has gained numerous applications.