Bench Wear Testing of Common Gasoline Engine Cylinder Bore Surface/Piston Ring Combinations

Abstract

In this study, two bench wear tests, the Cameron-Plint modified lest (C-P) and the Electro-Mechanical test (LS9), have been used to evaluate common internal combustion engine cylinder bore surface/piston ring pairs. Bore, materials tested include cast iron, 390 aluminum, and Nikasil. Piston rings tested include chromium-plated, plasma-sprayed molybdenum, and gas-nitrided stainless steel. Both the C-P and LS9 bench wear tests showed the same general trends. Gas-nitrided stainless steel rings provide the lowest overall ring wear and the lowest cast iron bore wear. 390 bore wear is higher than that of cast iron or Nikasil. Chromium-plated or gas-nitrided stainless steel rings provide the best balance of ring and bore wear against 390 aluminum, while molybdenum rings against 390 produce the worst combined wear. Differences in wear rates for 390 aluminum are related to variations in temperature and lubrication rate between the two testers. Bore wear measurement accuracy is quantified and an improved measurement technique is introduced. An initial study of surface finish effects shows that an increase in roughness increases the friction coefficient.