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Forged bearing steels and powder forged steels (e.g. AISI 52100, SAE 5160 and MPIF FL-4680) have been used to make cam lobes for assembled camshafts operating with roller followers. Application of powder metal (pressed and sintered) alloys to this and other components that operate under high rolling contact stress has been limited by relatively poor rolling contact fatigue (RCF) properties. This paper introduces developmental sintered steel alloys with high RCF strength. The density of these alloys is 7.4-7.6 Mg/m3 and the macrohardness is 500-800 HV. Endurance limits are in the range 1,700-2,280 MPa. The RCF endurance limit at 200 million stress cycles was determined using a testing rig. Camshafts for a 4.6 L V8 engine and a 4.0 L V6 engine have been assembled. These engines have a single overhead camshaft with end pivot rocker with roller follower (type 2 valve-train).

Power transmission components for automotive applications require high static and dynamic mechanical properties to insure long term system reliability. Historically, high quality wrought steel alloys have been the only materials used in the series manufacturing of high torque transmitting components such as one-way clutch races, transmission gears, sprockets and bearing races. Although powder metal technology offers lower cost components, limitations in static and fatigue properties of sintered materials preclude utilization of conventional powder metallurgy in these applications. To address these shortcomings we have developed DensiForm®, a surface densification technology. Specifically, a densification process is utilized with the net result of a full density layer on critical areas up to 1 mm deep into the part and an overall component density above 92% of the theoretical density.