Heat treatment of wear-resistant cast iron at high and low temperatures

Abstract

Electron probe microanalysis and X-ray diffraction analysis show that the maximum abrasive wear resistance of the 260Kh16M2 and 250Kh25MFT chromium cast irons with different types of carbides, Cr7C3 and Cr23C6, is provided by a metal base consisting of metastable retained austenite and martensite. This microstructure of the cast iron matrix before testing is created by high-temperature quenching with heating to temperatures of 1125-1170 °C and cooling in oil or in air. During operation, austenite on the working surface turns into dispersed martensite as a result of exposure to abrasive particles. Martensite, together with carbides, gives a high level of hardening and operability of the secondary microstructure of cast irons. An additional reserve of increasing the abrasive wear resistance of chromium cast irons by 20% consists in cold treatment after high-temperature quenching. The latter increases the content of cooling-induced carbon martensite before wear resistance testing and forms new portions of strain-induced martensite during testing.