Studying the chemical and phase compositions of a chromium-nickel-manganese steel after operation at elevated temperatures in corrosive environments

In recent years, chromium-nickel-manganese corrosion-resistant steels have been widely used in construction for the manufacture of stair railings and fences, elevators, and heat exchangers used for heat recovery in office premises and in production, including in metallurgical workshops. The purpose of this study is to determine the changes in the chemical and phase compositions of the 12Cr15Mn9NiCu corrosion-resistant steel (Russian analogue of the AISI 201 steel) after commercial operation in structural components of the heat exchanger of a metallurgical workshop. It was found that, during operation, all the studied fragments of the 12Cr15Mn2NiCu steel heat exchanger underwent intense oxidation with the formation of chromium and manganese oxides both on the surface and along the boundaries of the austenite grain. Diffusive penetration of sulfur into the steel with the formation of MnS particles, as well as carbonization of the surface layers, was recorded. As a result, the content of chromium and manganese in the steel significantly decreased, the amount of carbon increased, and the structure changed from austenitic to martensitic with a hardness of 532 HV 5 (48 HRC). Several investigated fragments retained austenite with oxidized grain boundaries. The austenite grain size ranged from 0.031 mm to 0.088 mm, with hardness ranging from 156 to 212 HV 5. It is shown that the use of the 12Cr15Mn9NiCu corrosion-resistant chromium-nickel-manganese steel intended for the manufacture of heat exchangers for metallurgical production is extremely inappropriate.