Search Results

Planetary gears in heavy truck gearboxes are normally manufactured by forging a blank, turning, hobbing, shaving and heat-treatment followed by grinding. Due to the size of the gear the net shape capability of PM methods can be cost effective alternatively to conventional manufacturing. Warm compaction and surface densification are two PM methods to reach high density and thereby high strength and fatigue properties. Typical characteristics for PM gears manufactured by these methods are outlined.

Selectively densified rollers from Distaloy DC-1, Astaloy Mo and Distaloy AE have been rolling contact fatigue (RCF) tested on a ZF-test rig. The rolling contact fatigue endurance limit of the Astaloy Mo based material is approximately 1500 MPa that can be compared to the selected reference material, AISI 5115 (DIN 16MnCr5), 1600 MPa. For the diffusion-alloyed materials, Distaloy DC1 and Distaloy AE, it was not possible to determine the endurance limit due to too few tests. However, the endurance limit seems to be slightly lower than the Astaloy Mo material. The case depth seems to be low for all materials, but the effect appears to be more severe for the Distaloy DC1 material. Surface cracks of different character could be found in all specimens. Small cracks associated with smaller pits are found on the run outs (>50·106 cycles).

Prototypes available for tests at an early development stage make it possible to reduce the lead-time for introduction of new P/M components for the automotive industry. This is of special importance for parts such as connecting rods, cam lobes and transmission gears etc. Pilot series of prototypes, made of high performing materials, have been warm compacted and evaluated with respect to material properties and robustness. Warm compaction is compared to other manufacturing techniques suited for high performing applications. Aspects of manufacturing and its capabilities are given. Material properties, the shaping ability of warm compaction and the specific demands caused by the operation of the component were taken into consideration at the early stage of design of the prototypes. For the most critical applications, the design of the prototypes has been optimised by Finite Element Analysis.