Abstract
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.
Highlights
As one of the main frictional pairs in the engine, the piston ring and cylinder liner have direct impacts on the engine’s mechanical efficiency and service life
Blok gave a criterion to judge the initiation of scuffing with the critical temperature, which was the sum of the bulk temperature and the flash temperature generated in the contact area [3]
As the lubricating oil is cut off, it enters into the oil starvation stage (OS) stage, and the balance of the tribological system is broken
Summary
As one of the main frictional pairs in the engine, the piston ring and cylinder liner have direct impacts on the engine’s mechanical efficiency and service life. Blok gave a criterion to judge the initiation of scuffing with the critical temperature, which was the sum of the bulk temperature and the flash temperature generated in the contact area [3]. Ludema proposed that wear debris agglomeration led to scuffing [6]. Enthoven and Spikes suggested that the onset of scuffing was always immediately preceded by the buildup of fine wear debris in the contact inlet [7]. Saeidi proposed that scuffing initiated when the tribo-film iron oxide reduced to iron and metal-metal contact and, adhesion took place [8]. Yagi observed the phase transformation of steel in the scuffing process under dry conditions, and the flattening of the whole contact area and dramatic expansion with changing the conformity seemed to play important roles in scuffing [9,10]. Yagi investigated the overall wear process with a combination of two-dimensional detector synchrotron X-ray diffraction (XRD), a near-infrared charge-coupled
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