PowderMet 2013: Innovative solutions to gearing challenges using Powder Metallurgy

October 2, 2013

A session titled “Technologies for PM Growth” took place during a Special Interest Program at PowderMet 2013, Chicago, June 24-27. During the session a presentation by Richard Slattery of Capstan Atlantic looked at how Powder Metallurgy can offer viable solutions in a number of gearing applications. Dr David Whittaker reports on his presentation exclusively for Powder Metallurgy Review and ipmd.net.

 

Capstan Atlantic is prominent among the PM companies who have succeeded in developing a range of PM solutions to gear applications. Although the major target of manual gear-box transmission gears remains elusive, the company has an impressive track record in penetrating other gear markets.

This track record was described in the presentation which was structured around a number of case studies of established applications, some of them past award-winning parts, and the technical solutions that have supported them. The featured case studies included:-

Crankshaft gear for a lawn & garden application

The technical requirements included sufficient elongation to allow a press fit on to a keyless mating shaft, good gear tooth surface finish to satisfy NVH issues, tooth wear resistance and durability and low involute profile lead error to minimise gear whine.

The solution involved the use of copper infiltration and surface rolling densification of a gear shape with customised tooth relief (Fig. 1).

fig-1

Fig. 1 Crankshaft gear for lawn & garden application [1]

Transfer case sun gear for a heavy duty off-road application

The technical requirements were for high density (for strength), high surface hardness (for wear resistance), good core ductility (for impact resistance) and precise tolerance of the involute profile and helix (for NVH performance).

The solution comprised the use of a modified (low core carbon) FLN2-4405 material at a minimum density of 7.5 g/cm³, providing a UTS > 1550 MPa. The parts are carburised (for wear resistance), shot peened (for surface finish improvement) and subjected to 100% NDT (for structural integrity validation) (Fig. 2).

fig-2_1

Fig. 2 Transfer case sun gears [1]

“High dense” transfer case sprockets

These sprockets replaced AISI 8620 forged sprockets and required a high UTS, extreme wear resistance and excellent NVH properties.

The solution involved the use of a low alloy, highly compressible raw material, processed to a high density in single compaction and with a carbonitrided case for wear resistance.

The gear design included a customised involute tooth shape for smooth chain roll-off (Fig. 3).

fig-3

Fig. 3 “High Dense” transfer case sprockets [1]

Bellville cup for a torque compensator in an all-terrain vehicle

The challenge in this application was to provide a wear resistant inner wall with precise spline and strong tabs for load resistance.

The tooling concept for this part included a lower punch action, designed for densification of the three outer tabs to 7.1 g/cm³, and powder transfer to the spline/flange region to achieve high density. The key part characteristics are spline size, counter-bore diameter, flange parallelism and run-out. These are tightly controlled dimensions.

The part is then subjected to a fixtured sintering treatment and a specially designed low distortion heat treatment, to maintain tolerance control.

The part is made from a modified FL-4405 material, through hardened to achieve a minimum UTS of 160,000 psi, a yield strength of 150,000 psi and a particle hardness of HRC 60 (Fig. 4).

fig-4

Fig. 4 Belville cup for torque compensator in all-terrain vehicles [1]

Crowned spur pinion

The challenge here was to modify the crowning on the 15-tooth transfix compound gear to reduce contact stress and increase gear life. System tolerances yield mesh angle errors across the gear flanks that result in high edge contact stresses (point loading) that exceed the 1200 MPa design specification, leading to early fatigue failure (Fig. 5). 

fig-5_copy

Fig. 5 Picture of gear mesh – a 15T spur gear       Fig. 6 Lead crown implemented to reduce edge

meshes with an effective 189T sector gear [1]     contact stress due to gear misalignment [1]

The solution was to implement a lead crown (Fig. 6) to reduce edge contact stress due to gear misalignment. The incorporation of a 0.01 mm crown to compensate for a 0.1 radian misalignment was shown to reduce stress to 922 MPa, well below the 1200 MPa design specification (Fig. 7).

fig-7

Fig. 7 Contact stress distribution with crown to compensate for misalignment [1]

References

[1] R H Slattery, Innovative Solutions to Gearing: Challenges Using Powder Metallurgy, as presented at PowderMet2013, MPIF, USA

Author

Dr David Whittaker is a consultant to the Powder Metallurgy and associated industries. Contact +44 1902 338498 email: [email protected]  

Dr David Whittaker is a consultant to the Powder Metallurgy and associated industries. Contact +44 1902 338498 email: [email protected]  – See more at: http://www.pm-review.com/articles/001587.html#sthash.dUVoZODj.dpuf
Dr David Whittaker is a consultant to the Powder Metallurgy and associated industries. Contact +44 1902 338498 email: [email protected]  – See more at: http://www.pm-review.com/articles/001587.html#sthash.dUVoZODj.dpuf

powdermet-logo

 

PowderMet2013 was organised by the Metal Powder Industries Federation. For more information please visit the MPIF website: www.mpif.org 

 

October 2, 2013

In the latest issue of PM Review…

Download PDF

Extensive Powder Metallurgy industry news coverage, and the following exclusive deep-dive articles and reports:

  • Phoenix Sintered Metals: A story of transformation, growth and community from America’s PM heartland
  • World PM2024 Yokohama: The stage is set for the PM industry to find a path to sustainable growth
  • The state of Europe’s hard magnets industry and the challenge of optimising the mass production of Nd2Fe14B permanent magnets

The latest news from the world of metal powders, delivered to your inbox

Don't miss any new issue of PM Review, and get the latest industry news. Sign up to our weekly newsletter.

Sign up

Join our community

Discover our magazine archive…

The free-to-access PM Review magazine archive offers unparalleled insight into the world of Powder Metallurgy from a commercial and technological perspective through:

  • Reports on visits to leading PM part manufacturers, metal powder manufacturers and industry suppliers
  • Articles on technology and application trends
  • Information on materials developments
  • Reviews of key technical presentations from the international conference circuit
  • International industry news

All past issues are available to download as free PDFs or view in your browser.

 

Browse the archive

 

Looking for PM production equipment, metal powders, R&D support and more?

Discover suppliers of these and more in our
advertisers’ index and buyer’s guide, available in the back of PM Review magazine.

  • Powders & materials
  • Powder process, classification & analysis
  • PM products
  • Atomisers & powder production technology
  • Compaction presses, tooling & ancillaries
  • Sintering equipment & ancillaries
  • Post-processing
  • Consulting & toll sintering
View online
Share via
Copy link