Comparison of the effects of low temperature austempering (LTA), quenching & partitioning (Q&P) and quenching & tempering (Q&T) processes on wear performance in high silicon cast steel

The present study was undertaken to investigate the wear performance of Low Temperature Austempering (LTA), Quenching and Partitioning (Q&P) and Quenching and Tempering (Q&T) processes in high silicon cast steel. With this object, the high silicon cast steel samples were produced by casting sand mold in a Y block shape and subsequently normalized at 910 °C. Within the scope of heat treatment studies, the samples were austenitized at 900 °C for 30 min, and the first batch of samples was austempered in a salt bath at 280 °C for 120 min for low temperature austempering process. After austenitizing at the same conditions, the second batch of samples was exposed to oil quenching at 180 °C for 10 min followed by partitioning at 280 °C in a salt bath for 110 min to keep applied heat treatment time the same. As Quenching and Tempering process is frequently used when the wear properties comes, as a benchmark group third batch samples were quenched in oil at room temperature for a few minutes and tempered at 280 °C for 120 min. In the characterization studies, ball on disc tribometer, hardness test, XRD analysis, optical microscope, Field Emission-Scanning Electron Microscope (FE-SEM) and optical profilometer were utilized. The findings of this study indicated that while austempered samples consisted of carbide free bainitic structure (CFB), the samples went through a Q&P process included tempered martensite as well as CFB structure. The third group samples quenched and tempered contained tempered martensite. The lowest amount of austenite was determined in the Q&T process with about 11%, while approximately 17% volume austenite was determined in both Q&P and LTA processes. In general, both LTA and Q&P processes considerably increased the wear performance compared to the normalized condition and Q&P process is superior to LTA process and is a very competitive option in terms of wear resistance against Q&T process.