Over the last years heat treatment concept of “quenching and partitioning” (Q&P) has reached popularity for its ability to precisely adjust material properties to desired values. Mostly, Q&P process are applied on tailor-made materials with high purities or prototype alloys. The research in hand presents the whole routine of how to investigate the potential of a commercial 0.54C-1.45Si-0.71Mn spring steel in terms of Q&P heat treatment from lab scale in dilatometer measurements to widely used inductive heat treatment on larger scale. In order to obtain the small process window for this material we were focusing on the interplay of the formed microstructure and the resulting mechanical properties in hardness measurements, compression tests as well as tensile tests. After full austenitizing, three different Q&P processing routes were applied. Microstructural analyses by optical microscopy, Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD) exhibit a condition with 6.4% and 15% volume fraction of fine distributed retained austenite. Interestingly, the 15% of retained austenite developed during the partitioning heat treatment. Contradictory to our expectations, tensile and compression testing were showing that the 6.4% condition achieved improved mechanical properties compared to the 15% retained austenite condition. The remarkable conclusion is that not only volume fraction and fine distribution of retained austenite determines the potential of improving mechanical properties by Q&P in commercial alloys: also the process step when the retained austenite is developing as well as occurring parallel formation of carbides may strongly influence this potential.

In order to achieve the desired properties, the microstructure of metals is often modified by heat treatments. A suitable combination of high strength and good ductility can be achieved by adjusting the amounts of martensite and retained austenite through a Quenching and Partitioning (Q&P) process. Controlling these material properties offers new potentials in the production of light weight steel parts. This paper presents a basic study of heat treatment conditions with subsequent microstructural characterization of quenched and partitioned commercial 0.54C-1.45Si-0.71Mn spring steel. Beginning from full austenitization, different quenching and partitioning parameters were applied. Microstructural characterization was performed using optical microscopy in combination with different etching methods as well as Scanning Electron Microscopy (SEM) and Electron Backscattered Diffraction (EBSD). It is shown that the intended dual phase microstructure with a specific phase fraction of austenite can be produced. Those results and consideration of hardness measurements show that the investigated commercial spring steel is a promising candidate for improving mechanical properties by a Q&P process.