Investigation on Manganese Sulfide Inclusion Sizes in 50CrMo4 Steels by means of Fractography, Micrograph Analysis and Immersion Ultrasound

Abstract

Abstract Increasing loads in powertrain components have put manganese sulfide inclusions in the spotlight of engineers. The indigenous sulfides are accounted responsible for the poor fatigue performance of highly loaded steel parts. In order to relate fatigue performance to manganese sulfide inclusion size, an accurate geometrical description of the sulfides is necessary. Fatigue testing generally reveals maximum inclusion sizes, since the largest inclusions will initiate fatigue failure. Micrograph analysis and immersion ultrasonic testing have been carried out in order to compare those methods with the referenced values of fatigue testing. It showed that immersion ultrasound is not capable of detecting manganese sulfide inclusions of the present sizes. Micrograph analysis, however, is applicable, if analysis data is modified subjectively.