PISTON-RING COATINGS FOR HIGH HORSEPOWER DIESEL-ENGINES

Thermal-spray-deposited face coatings were developed for a top compres sion piston ring operating under the high pressures and temperatures o f high horsepower diesel engines. Coatings were deposited by plasma sp ray and high velocity oxygen fuel (HVOF) techniques onto the piston ri ng faces. The coatings were evaluated by wear and engine tests. Three coatings were deposited by a plasma spray technique: molybdenum/chromi um 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 c arbide, plasma-sprayed chromium oxide and plasma-sprayed molybdenum/ch romium carbide were identified to have wear resistances superior to th at 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 chromi um.