PISTON-RING COATINGS FOR HIGH HORSEPOWER DIESEL-ENGINES

Thermal-spray-deposited face coatings were developed for a top compression piston ring operating under the high pressures and temperatures of high horsepower diesel engines. Coatings were deposited by plasma spray and high velocity oxygen fuel (HVOF) techniques onto the piston ring faces. The coatings were evaluated by wear and engine tests. Three coatings were deposited by a plasma spray technique: molybdenum/chromium carbide, molybdenum/molybdenum carbide, and chromium oxide. Nickel chromium/chromium carbide powder was deposited by a HVOF technique. On the basis of wear and engine testing, HVOF nickel chromium/chromium carbide, plasma-sprayed chromium oxide and plasma-sprayed molybdenum/chromium carbide were identified to have wear resistances superior to that of today's electroplated chromium and molybdenum carbide coatings. Cylinder liner wear was found to be generally equivalent or lower for the thermal spray coatings when compared with the electroplated chromium.