PISTON RING COATING REDUCES GASOLINE ENGINE …

1 DE VELO PMENT friction PISTON ring COATING REDUCES . GASOLINE ENGINE friction . Federal-Mogul has developed a COATING system for PISTON rings under the name of Carboglide which decreases wear in highly charged GASOLINE engines and further REDUCES friction losses which occur between the ring pack and the cylinder running surface. The tailored composition of the specific layer structure of the carbon-based Carboglide COATING in combination with corresponding modified PISTON ring designs yields a potential to improve fuel efficiency by up to %.

2 40. A U T H OR S REQUIREMENTS bochemical reactions. In most tribologi- cal systems these properties result in a Manufacturers of internal combustion lower coefficient of friction under engines continually face the challenge boundary lubricated conditions when to reduce fuel consumption and emis- the COATING is compared to other COATING sions by improving ENGINE efficiency. In systems (such as metallic layers, hard particular this necessitates a substantial coatings and others). DR. MARCUS KENNEDY reduction of mechanical frictional Using carbon-based coatings for pis- is Manager Physical Coatings at losses.

3 The components of the power ton rings necessitated a significant fur- Federal-Mogul in Burscheid cylinder and crankshaft drive are at the ther development of this COATING tech- (Germany). center of these development efforts. The nology to meet the tougher require- PISTON ring pack has a significant poten- ments of surface fatigue resistance and tial for bringing down friction losses COATING fatigue. Based on the develop- due to its fairly high (24 %) share of ment of the GOE245 metal-doped, mechanical frictional losses, 1.

4 At the hydrogenated carbon COATING the first same time measures such as direct series application for highly loaded pas- injection and turbocharging among others, senger car GASOLINE engines succeeded DR. STEFFEN HOPPE. which increase ENGINE performance, in 2006. GOE245 significantly reduced is Director Technology Rings and Liners at Federal-Mogul intensify the requirements for the func- the previously observed cylinder sur- in Burscheid (Germany). tional behaviour of PISTON rings. face scoring which led to scuff-mark When considering measures to opti- formation under the harsh tribological mise the tribological system of PISTON conditions in these AlSi cylinder sur- ring and cylinder surface, PISTON ring face engines.

5 As the damage mecha- coatings play an increasingly important nism is most frequently seen under cold role as they can directly influence the start conditions, this carbon-based wear and friction behaviour and the COATING is typically chosen and used as JOHANNES ESSER resulting scuff resistance. By introduc- a running-in COATING applied onto a is Director Engineering Rings ing Carboglide Federal-Mogul is provid- wear resistant COATING (nitrided layer, and Liners at Federal-Mogul in ing a COATING for PISTON ring applications PVD layer) [2].

6 Burscheid (Germany). which meets the most stringent require- During the subsequent development ments for functional behaviour and work the level of COATING wear was sub- offers a considerable potential to reduce stantially reduced by introducing the frictional losses. GOE247 COATING . This PISTON ring COATING consists of several layers which com- prise an amorphous hydrogenated car- CARBON-BASED PISTON ring . bon top layer which is applied onto a COATINGS. metal-doped and hydrogenated interme- Carbon-based coatings (DLC, Diamond- diate carbon layer.)

7 The PISTON ring coat- like Carbon) have a long track record in ing is applied with a layer thickness of applications for cutting tools and com- 3 to 5 microns and shows a wear resist- ponents that are tailored for the most ance in the ENGINE which is higher by a severe tribological requirements [1]. factor of 4 to 5 when compared to the Diamond-like carbon coatings have only performance of a metal-containing DLC. a low tendency for adhesive wear or tri- PISTON ring COATING . 1 Energy distribution diagram showing friction losses in GASOLINE engines with the proportionate share of the PISTON rings 0 5 I 2 012 Volume 73 41.

8 DE VELO PMENT friction Schematic Scanning electron micrograph of the COATING representation of on a top ring on nitrided chromium steel the Carboglide layer structure on a PISTON ring COATING STRUCTURE AND carbide is embedded in the form of in demonstrate that the scuff resistance PROPERTIES nanocrystals found in a column-shaped is nearly twice that of a PVD coated pis- growth pattern. The top layer is an ton ring running surface. The combination of direct injection and amorphous diamond-like carbon layer turbocharging with very smooth cylinder which is characterised by a specific ratio FUNCTIONAL BEHAVIOUR DURING.

9 Running surfaces, in GASOLINE engines, sig- of sp2 and sp3 bonded carbon. By adjust- ENGINE OPERATION. nificantly increases the demand for PISTON ing the layer thickness ratio of the top rings with excellent scuff resistance and layer to the intermediate layer to a value The beneficial functional behaviour of low cylinder running surface wear. between to while adjusting the the new COATING was extensively tested The necessity to reduce fuel consump- relation between top layer and total coat- under real ENGINE conditions.

10 The first tion and thus CO2 emissions requires an ing thickness to between and the series applications in highly charged increasing contribution of the reduction level of residual COATING stress is modi- GASOLINE engines demonstrated the dura- of frictional losses. fied so that the total COATING thickness is bility under field conditions . The In order to meet these tough require- roughly 10 microns, . Furthermore the development of a new generation of ments which translate into very low high level of COATING hardness, measur- PISTON ring COATING that serves to signi- friction in combination with high wear ing between 1800 and 3100 , in ficantly reduced frictional losses has resistance and superior scuff resistance, combination with a COATING thickness.