This case study focuses on a spur gear made of AISI 5120, a low carbon alloy steel used for a wide range of applications in the automotive industry due to its versatility. In LPC, convex (outer) surfaces and concave (inner) surfaces affect the carbon uptake differently due to local diffusion dynamics. Concave surfaces like the inner radius of the root fillet will often have a shallower case depth and lower carbon than convex surfaces like the flank of the tooth. The selected gear geometry is a spur gear with an outer flank radius of about 6.2 mm and an inner radius of about 0.76 mm. The goal is an effective case depth of 1 mm with 0.35 wt% carbon (~50 HRC) at that depth and a final surface carbon of ~0.8 wt%, producing about 50-60 HRC after quenching.