Low pressure carbonitriding (LPCN) has the potential to improve the impact and fatigue strength of steel components through the enrichment of nitrogen and the effect of carburizing at higher temperatures. The work described in this paper investigates the influence of boron on the LPCN response of 20MnCr5 steel and the effect of niobium on that of 8620. LPCN treatments were developed to achieve a surface hardness of ~700 HV and case depth of 0.65-0.75 mm in four alloys: 20MnCr5, 20MnCr5 + B, 8620, and 8620 + Nb. The hardness and case microstructure of treated and quenched test samples are correlated with bending fatigue measured in Brugger fatigue specimens, which simulate the root of a gear tooth.

Flash Bainite Processing employs rapid thermal cycling (<10s) to strengthen commercial off the shelf (COTS) steel sheet, plate, and tubing into AHSS. In a continuous process, induction technology heats a narrow segment of the cross section in just seconds to atypically high temperatures (1000-1300°C). Quenching substantially immediately follows. Flash Processing utilizes inherent heterogeneity of steel creating multi-chemistry, complex mixtures of approximately 20% bainite and 80% martensite. Carbide dissolution and carbon migration are controlled by limiting time in the austenite temperature range. Unlike conventional heat treating to create advanced high strength steels (AHSS), homogeneity is intentionally avoided and non-equilibrium conditions are created. The leanest prior ferritic regions transform to bainite while prior pearlite forms martensite. A 7-10% higher yield/tensile strength product results with the beneficial ductility of the bainite constituent. Flashed AISI1010 (1100MPa UTS) and AISI1020 (1500MPa UTS) have shown exceptional room temperature stamp-ability to 0T/1T bend radii. The 1500MPa formability of 3G-AHSS is achievable. Flash Bainite offers simultaneous weight and cost savings.