No abstract

The quest for safety improvement with weight reduction of vehicles and consequently lower fuel consumption, led the automotive industry to begin research into the third generation of advanced high strength steels. These steels present complex microstructures, composed of martensite, bainite and stable retained austenite. Two of the main treatments for obtaining these microstructures are the low temperature austempering and Quenching and Partitioning (Q&P). The objective of this work is to evaluate the microhardness and adhesive wear performance of a high silicon steel alloyed with niobium submitted to the treatments mentioned above. The austempering treatment was conducted at 340 °C for 1 and 3 hours. Partitioning steps in Q&P were performed at 250 °C for 10, 30 and 60 minutes. Results shows that niobium addition promotes changes in the bainite morphology which improved the wear resistance.

Austenitic stainless steels form the largest family of alloys in terms of number and applications. They are characterized by having good toughness, weldability, cold formability, and corrosion resistance in various situations. However, because they cannot harden by heat treatment, they exhibit low wear resistance. Suitable coatings can increase their wear resistance and expand their usability range. Boride coatings, with their high hardness and wear resistance are a good candidate for this purpose. In this work, samples of stainless steels, AISI 304 and UNS S31254, were subjected to liquid boriding at 950°C for 2 and 4 h. Optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Vickers hardness tests were performed, along with tests for micro-adhesive wear (fixed-ball type). The boriding treatment resulted in the formation of layers with high hardness, in the range of 1800 to 2000 HV, which is typical for boride layers. Micro-adhesive wear tests demonstrated the great increase in wear resistance obtained through this treatment.