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. It wears 40% less, increasing service life. The lower wear of NSR improves control of lubricant oil consumption and blow-by during engine life. Keeping these values low is essential to achieve lower pollutant emissions. The better stiffness of steel allows use of narrower rings with reduction in friction opening potential to improve fuel economy.