Structure and Surface Properties of Metastable Austenitic Steel Subjected to Liquid Carburizing at a Reduced Temperature

Abstract

This work investigates the effect of liquid carburizing at 780°C on the structure, chemical and phase composition, microhardness, and surface roughness of corrosion-resistant austenitic chromium-nickel steel. The depth of the carburized layer has been determined to be about 2 mm. The steel structure at a distance of 0.15 mm from the surface consists of carbon-saturated austenite γC, α' martensite, and fine Cr23C6 chromium carbides located along austenitic grain boundaries. No carbides are observed in the grain body. There are austenite γC and chromium Cr23C6 carbides in the structure at a depth from 0.15 to 2 mm. The number and the size of carbides decrease with distance from the steel surface. Carburizing increased the microhardness of the steel surface by a factor of four (from 200 to 800 HV0.025) and the roughness parameter Ra to 1.35 μm.