The tribological properties of a new unique thermo-reversible Gel-Lubricant (TR Gel-Lube) were investigated. TR Gel-Lube which includes 10-40% of amide type gel agent in base fluid, is repeatedly able to change from gel-state to liquid-state at the melting point of its gel agent. TR Gel-Lube can be used as an impregnant for porous-material due to its physical state change. TR Gel-Lube indicated lower frictional and better lubricating properties than that of conventional greases. In particular, when TR Gel-Lube was sintered in a copper-type sintered bearing, a lower friction coefficient compared with oils was observed. In this study, to clarify the mechanisms of TR Gel-Lube, the behavior of gel agent on the EHL region was investigated by ball-on-disk tribometer. It was found that gel agent played a key role in the lubricating properties. Some mechanisms such as adsorbed film formation, smooth surface formation and solid like film formation are proposed.
The authors tested the effects on the tribological characteristics of refrigeration oils under refrigerant atmospheres using a block-on-ring tribometer. Based on the results of a sliding test using the tribometer, it was found that tricresyl phosphate (TCP) in both a polyol ester (POE) and alkylbenzene (AB) oil formed a lubricating film on the sliding surface under R410A atmosphere. Surface analyses revealed that a phosphate film had been formed on the sliding surface. With the POE oil in particular, the anti-wear effect of TCP greatly reduced the width of the wear track. It was also found that R32 interferes with the formation of phosphate films to a greater extent than does R410A. It is thought that the high polarity and the high reactivity of R32 with nascent metal surfaces prevent TCP from adsorbing to the Fe of the sliding surface. These results show that not only refrigeration oils but also refrigerants can have a major effect on the formation of the phosphate film in refrigeration systems. This knowledge could be helpful when designing new refrigeration systems.
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