A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y / F E B R U A R Y 2 0 2 3 3 6 Increasingly restrictive exhaust emissionslawsfordieselengineshavedriven changes in engine design. Higher combustion pressure, higher operating temperatures, and less lubrication than previous designs have been placed on engine components such as engine valvetrain components, which have experienced increased wear rates in many cases. Another emerging trend in diesel and natural gas engine development is the use of exhaust gas recirculation (EGR), a process by which exhaust gas is partially routed back into the intake air stream to reduce nitric oxide (NOx) content in exhaust emissions. The use of EGR in diesel engines can change engine combustion characteristics and consequently the valve and valve seat inset (VSI) working environment. In addition, engine exhaust gas contains compounds of nitrogen, sulfur, chlorine, and other elements that can potentially form acids. Thus, good corrosion resistance is also a basic requirement for VSI alloys. REDUCED COBALT USAGE To meet the challenges placed on new diesel and natural gas engine valve train components, cobalt-based alloys such as J3 and J10 have been widely utilized for VSI production. Alloy J10 contains 60 wt.% cobalt, while J3 contains 50 wt.% cobalt; hence, a significant amount of cobalt is used for diesel and natural gas engine applications. More than 600 metric tons of cobalt was used to make engine VSIs in 2021, as shown in Fig. 1. Therefore, concerns have increased regarding the sustainability of these significant amounts of cobalt usage, as well as the high cobalt costs. LEJalloy J513 isdesigned for higher wear resistance and reduced cobalt use. The primary approach of the alloy design includes: desired solidification TABLE 1 — NOMINAL COMPOSITION OF LEJ PRIMARY COBALT CONTAINING ALLOYS, WT% Alloy C Si Mn Cr W Mo V Nb B Fe Ni Co J3 2.4 0.75 0.2 30.0 12.5 0.4 - - - 3.0 max 3.0 max bal J10 0.04 2.4 - 8.15 - 28.5 - - - Fe + Ni : 3.0 max J100 2.5 0.75 0.35 28.0 15.00 - - - - 5.0 bal 10.0 J160 1.45 0.6 0.30 12.75 4.0 5.5 1.15 1.9 - bal 0.4 J513 2.1 0.5 0.35 15.5 1.5 12.0 - - 0.05 bal 2.1 19.5 Fig. 1 — Cobalt usage for VSI production with LEJ primary cobalt-containing alloys. TECHNICAL SPOTLIGHT SUSTAINABLE ALLOY SOLUTION FOR ENGINE VALVETRAIN APPLICATIONS J513 alloy offers lower costs and higher performance for diesel and natural gas engine applications while also requiring substantially less cobalt usage. Fig. 1 — Cobalt usage for VSI production with LEJ primary cobalt-containing alloys.