Effect of nitrogen alloying on the microstructure and abrasive wear of stainless steels

Alloying stainless steels with nitrogen has distinct advantages. Nitrogen is a strong austenite stabilizer and a potent solid-solution strengthener, and nitrogen has greater solubility than carbon in iron. This study investigates the relationship among nitrogen concentration, precipitate microstructure, and abrasive wear using two high-nitrogen stainless steel alloys: Fe-19Cr-5Mn-5Ni-3Mo (SSI) and Fe-16Cr-7Mn-5Ni (SS2). Alloy SSI contained 0.7 wt% N and was solution annealed at 1150 °C, thereby dissolving the nitrogen interstitially in the austenite. Subsequent aging, or cold work and aging, at 900 °C led to the grain-boundary, cellular, and transgranular precipitation of Cr ₂ N. Alloy SS2 was remelted in a highpressure (200 MPa) N ₂ atmosphere, leading to a spatial gradient of nitrogen in the alloy in the form of interstitial nitrogen and Cr ₂ N and CrN precipitates. Nitrogen contents varied from a low of approximately 0.7 wt % at the bottom of the billet to a high of 3.6 wt % at the top. Nitrogen in excess of approximately 0.7 wt% formed increasingly coarser and more numerous Cr ₂ N and CrN precipitates. The precipitate morphology created in alloy SSI due to aging, or cold work and aging, had little effect on the abrasive wear of the alloy. However, a decrease in the abrasive wear rate in alloy SS2 was observed to correspond to the increase in number and size of the Cr ₂ N and CrN precipitates.     

New nitrogen-bearing austenitic stainless steels with high strength and ductility

The effect of nitrogen on the strength, ductility, and corrosion resistance of nitrogen-bearing austenitic stainless steels is studied. Fields of application of these steels are considered.     

Effect of heat treatment on the wear resistance of high-carbon and high-nitrogen steels subjected to abrasive wear

The effect of quenching and tempering on the capacity of steels based on chromium-carbon, chromium-nitrogen, and carbon-manganese austenite for strain-induced martensitic transformation, hardening, and wear resistance in the process of abrasive wear is studied. The steels contain 1–1.2% C or N and 18% Cr or Mn. The wear resistance of the studied steels having a structure of metastable austenite is compared to that of steel 110G13. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 29–33, April, 2006.     

热处理对钼铜奥氏体不锈钢组织和耐腐蚀磨损性能的影响

研究了热处理工艺(不同固溶温度和固溶时间)对钼铜奥氏体不锈钢析出物含量和形态的影响,以及在不同固溶温度下材料的耐腐蚀磨损性能.试验结果表明,钼铜奥氏体不锈钢析出物随固溶温度的升高和固溶时间的延长而增多,其形态也由针棒网状长成块状;在纯磨损环境下,1100 ℃×8 h空冷下的奥氏体不锈钢析出物数量最多,耐磨损性能最好;而在有酸的腐蚀磨损环境介质中,950 ℃×8 h空冷的热处理工艺下的材料耐腐蚀磨损性能最佳.     

Effect of alloying elements on the structure of cast hypereutectoid steels after heat treatment

Conclusions In selecting a treatment schedule providing uniform distribution of carbides in cast hypoeutectic steels for rolls it is necessary to take account of the fact that the cementite network along grain boundaries dissolves in the temperature range 850–950°C. In steel with a low content of carbide-forming elements eutectic cementite does not dissolve at these temperatures. As the heating temperature is increased from 850 to 1100°C intense surface graphitizing commences, which points to the possibility of forming graphite inclusions with bulk heat treatment. With an increase in the content of chromium and molybdenum in steel the graphitizing process is suppressed, and carbon is bonded into stable carbides. In such a steel eutectic carbides dissolve at 1050–1100°C. Preparation of a structure with uniform carbide distribution during heat treatment is only possible in steels containing about 2% Cr and not less than 0.3% Mo.Ukrainian Research Institute of Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 62–64, August, 1987.     

Effect of prior heat treatment on the structure and properties of nitrided steels

Conclusions