LEFT: High temperature applications such as turbocharger wastegate shaft bushings and EGR valves are currently reliant on Cobalt use to provide wear resistance in high temperature ranges and �i�� �enefit �rom t�e use of new materials.
COBALT
Cobalt is a chemical element with the symbol Co and atomic number 27. Apart from small deposits found in alloys of natural meteoric iron, it is found in the Earth’ s crust only in chemically combined form. The free element that is produced by reductive smelting is a hard, lustrous, silver-grey metal.
Cobalt is primarily used in lithiumion batteries and in electroplating, and in the manufacture of magnetic, wear-resistant and high-strength alloys. Cobalt salts are used to impart blue and green colours in glass and ceramics and radioactive Cobalt is used in the treatment of cancer.
Today, some Cobalt is produced s�ecifically from one of a number of
ores, such as Cobaltite( CoAsS) but it is more usually produced as a by-product of Copper and Nickel mining. Most comes from the Democratic Republic of the Congo( DRC), currently accounting for more than 60 per cent of the global production, although there are also lesser sources in Russia, Australia, Cuba, Philippines, Madagascar, New Guinea, Canada, New Caledonia, South Africa and the USA.
An unfortunate and important consideration is that Cobalt mining has often been associated with child and slave labour, primarily in the mines of the DRC, and contact with Cobalt is associated with cancer, respiratory problems and skin complaints. Technology companies seeking an ethical su��ly chain ha�e conse�uently faced shortages, as well as increasing costs due to its risin� re�uirements�
Images © Tenneco Inc.
Tenneco Inc.’ s Powertrain business group has developed an innovative new material which delivers wear-resistant performance with greatly reduced Cobalt content, helping engine manufacturers mitigate the limited availability and price volatility of Cobalt.
The new material will be of great benefit in the demandin� hi�h temperature applications that typically rely on Cobalt to provide wear resistance in high temperature ranges, such as heavy-duty turbocharger wastegate bushings, EGR valves, and high-performance valve seats. Using an alternative sintered steel formulation, trials have shown that the Cobalt content in Tenneco’ s sintered materials can be reduced si�nificantly, without compromising wear resistance.
Gian Maria Olivetti, Vice President Global Engineering at Tenneco
Powertrain explains:‘ Potential material shortages and controversy around Cobalt mining, coupled with extreme price volatility, mean we must reduce our dependence on Cobalt. While it remains the most effective material to combat wear in dry running valve seat applications and other components subjected to big temperature ranges, we have used our extensive experience in powder metallurgy to develop a low- Cobalt sintered formulation alternative that delivers similar wear properties to the best current materials.’
The application temperatures for bushings in EGR valves, turbocharger wastegate systems or exhaust-gas valves can range from below 0 ° C up to 1000 ° C, and it is this wide variation that makes the tribology challenging, as Jens Wellmann, Tenneco Powertrain product manager for turbocharger
components, explains.‘ Especially in the lower temperature range up to ~ 400 ° C high-Cobalt materials can outperform the typical non-Cobalt materials. The first �uestion we had to answer was�‘ What is the explanation for high- Cobalt material’ s low wear rates?’ And the second �uestion was� ��ow much Cobalt is effectively needed to produce that effect?’
Tenneco’ s research started from two well-proven existing sintered products; FM-8100, an iron-based Cobalt-free sintered material, and FM-T95A, a Cobalt-based( 54 % Cobalt by weight) sintered material comparable to the cast materials used for tribological applications. Between these two e�tremes, a total of fi�e materials with varied Cobalt content were evaluated for wear performance across a range of temperatures. Investigation... P
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