Comparison of Heavy-Duty Scuffing Behavior between Chromium-Based Ceramic Composite and Nickel-Chromium-Molybdenum-Coated Ring Sliding against Cast Iron Liner under Starvation

A running-in and starved lubrication experiment is designed to investigate the heavy-duty scuffing behavior of piston ring coatings against cast iron (Fe) cylinder liner using the piston ring reciprocating liner test rig. The scuffing resistance of the piston ring with the chromium-based ceramic composite coating (CKS), and that with the thermally sprayed nickel-chromium-molybdenum coating (NCM) is compared at different nominal pressures (40~100 MPa) and temperatures (180~250 °C). With the failure time as a criterion, the rank order is as follows: NCM/Fe > CKS/Fe. Before the scoring occurs at the interface of the piston ring and cylinder liner (PRCL), the cast iron liner enters into a "polish wear" stage, and iron-based adhesive materials begin to form on the piston ring surface. With the macroscopic adhesion formation, the plastic shearing cycle causes surface damages mainly due to abrasive effects for the CKS/Fe pairs and adhesive effects for the NCM/Fe pairs.