Federal-Mogul Powertrain has upgraded its Goetze Diamond Coating (GDC) for piston rings, a technology used ub heavy-duty diesel engine requirements for over 10 years. The new coating, GDC60, has higher diamond content to further reduce wear and has demonstrated lower friction and greater scuff resistance during testing.
“GDC60 will enable our customers to develop new, more efficient engines with higher cylinder pressures while staying with a familiar, well-proven ring coating technology,” said Gian Maria Olivetti, chief technology officer. “This means they can continue to benefit from design features such as the inlays and Blitzchrom flank protection that are already well established in the market with GDC50, as well as lower validation costs compared to a completely different ring coating technology.”
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The GDC coatings are galvanic, enabling use of the very high coating thicknesses required for heavy-duty engines. As cylinder pressures increase, however, greater scuff resistance is required, especially for the first compression ring. The challenge has been to maintain the high robustness and cost-effective design advantages associated with GDC coatings while meeting the increased demands.
In rig tests, GDC60 reduced the friction coefficient up to 7% and first engine tests have shown the potential for wear reduction of up to 10% compared to GDC50 coatings. This will also benefit the function of the oil rings.
In order to provide GDC60 with greater scuff resistance under high thermal load conditions, the supplier has improved upon the microstructure of GDC50, creating a finer microcrack network containing increased numbers of nanodiamond particles that are also more uniformly distributed.
When conventional fresh oils are used, GDC60 shows a scuff resistance improvement of up to 20% on already high levels of thermal load capacity; the improvement is even higher when operating with aged oil. Confirmation studies carried out with very low viscosity lubricating oils (HTHS2.6) demonstrated that GDC60 can withstand the same thermal load level as PVD (physical vapour deposition) coatings.
For specific applications, increased scuff resistance in combination with the proven high level of robustness under borderline loads makes GDC60 the optimum technical option within conventional piston ring coating families. Initial results from endurance testing in a highly loaded heavy-duty engine have confirmed the results of the rig test investigations.
GDC60 will complement the wide portfolio of piston ring coatings offered by Federal-Mogul Powertrain. Comprising galvanic, PVD and other technologies, the range also includes the premium DuroGlide product, an amorphous carbon-based coating that contains a high percentage of diamond-like-carbon and which set a new benchmark for low friction and wear when introduced in 2014.
