Novel nanostructured bainitic steel grades to answer the need for high-performance steel components (Nanobain).

This report summarises the work carried out over the duration of the project. The aim of this project was to investigate the fatigue and wear properties of Si-rich nanostructured bainitic steels (Nanobain). A first phase of the project consisted in the design of different possible alloy compositions, divided into a first series tailored for the manufacture of small components using gas quenching, and a second series for the manufacture of larger sections heat-treated in a salt bath. Kinetics and basic mechanical properties were investigated on laboratory casts. During this first part, an unprecedented combination of tensile strength and ductility was achieved on a newly designed composition (UTS 2.2GPa, total elongation > 20 %). Wear rates as measured in twin-disc tests were as little as 50 % of those achieved on standard high-hardness bainitic grades. In a second phase, two industrial heats were produced on the basis of results achieved during the first part of the project. These were used to manufacture component demonstrators or actual components and test them in representative conditions. Thus, tests on a metal scrap shear were carried out on the 0.6 %C grade designed in this project and heat-treated at 280 °C. Results were promising although testing conditions make it difficult to achieve a direct comparison. METSO estimates that this could provide similar performance as largely more expensive alloys, thus bringing a 10–20 % economic improvement. Fatigue testing at Bosch also led to promising results, with fatigue performance of the 06C grades on a par with those of 100Cr6. In contrast, results achieved on 1CSi were relatively poor, possibly due to poor cleanliness of the steel.