Increasing the Abrasive Wear Resistance of High-Chromium Steel after Cold Treatment

Abstract

Ways to increase the abrasive wear resistance of high-chromium steel depending on changes in the temperature of heating for quenching and cold treatment are studied in this paper. It was found that during quenching from temperatures of 850-1000 °C, martensite is formed in the structure of steel H12МFL, which provides high hardness: however, maximum abrasion resistance is not achieved in conditions of abrasive wear. An increase in the heating temperature for quenching to 1170 °C leads to a decrease in the initial hardness, which is due to the dissolution of carbides and an increase in the amount of residual austenite, but this is accompanied by a significant increase in wear resistance in abrasive wear. Residual austenite, obtained as a result of high-temperature hardening (from 1170 °C), is metastable and, in the process of wear, becomes a deformation-induced martensite. This gives the steel maximum wear resistance due to its high frictional hardening ability. A further increase in the temperature of heating for quenching above 1170 °C is inexpedient, since it leads to grain growth. Additional possibilities for increasing abrasive wear resistance consist of the cold treatment of high-carbon steels because of an increase in the amount of cooled martensite and an increase in the initial hardness. Cold treatment of the test steel after high-temperature quenching with cooling to minus 70 °C for 20 min and low tempering at a temperature of 200 °C for 2 h allows for further increases to the abrasion resistance by 25% due to the formation of 15% high-carbon chromic martensite cooling and initial hardness up to 60 НRC, with the preservation of 20% of residual metastable austenite and carbides.