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Due to several market demands of higher wear and scuffing resistance, Duplex PVD (Physical Vapor Deposition) CrN top ring has been used in Heavy Duty Diesel (HDD) engines. The ring comprises a nitrided high chromium stainless steel with a PVD ceramic CrN coating. For High Speed Diesel (HSD) vehicles with lower demands, MAHLE has developed an alternative PVD coated ring, which balances the cost and performance ratio. This alternative, named High Value PVD (HV-PVD), consists of applying the best resistant coating for wear and scuffing, PVD, onto a less costly ring material, Ductile Cast Iron. The HV-PVD top ring has been tested in HSD engines and shown excellent performance. Additional advantages of the HV-PVD are its lower friction coefficient and better tribological compatibility with the cylinder bore materials when compared to the traditional galvanic chrome based coatings. Such features lead to reduced engine friction and lower cylinder wear.

This work compares the typical manufacturing process of cast iron piston rings with chromium or molybdenum coating with the more recent nitriding steel process. Environmental impact of the processes is estimated by their material losses, consumption of energy and hazardous waste. Despite all technological development, the nowadays production process of a typical piston ring still implies that the finished part has only 30% of the iron initially cast. A more recent design, nitrided steel piston ring, reduces substantially material losses during the part manufacturing. It also substitutes high polluter processes as chromium plating or metal spray for the lower polluter gas nitriding. Production of Nitrided Steel Rings (NSR) uses 40% less energy, needs 78% less raw material and produces almost 10 times less hazardous waste. NSR has significant lower environmental impact in comparison with the traditional Coated Iron Ring (CIR). NSR also has environmental advantages during use.