THE CUTTING PERFORMANCE AND TRIBOLOGICAL CHARACTERISTICS OF SYNTHETIC ESTER LUBRICANTS SUITABLE FOR MQL MACHINING

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The purpose of this study is to understand the action mechanism of synthetic ester lubricants suitable for MQL machining by investigating their tribological characteristics and cutting performance. The main results and conclusions of this study are as follows.1. Tribological characteristics evaluation of synthetic estersAccording to a survey of suitable esters for MQL machining, this study investigated the lubricating characteristics of those esters by a basic friction test and found that an ester having more ester bonds in one molecule showed the better lubricity and such trend was prominent at higher sliding speed.2. Evaluation of cutting performance by practical MQL machining testsThe practical MQL machining of alloy steels by turning illustrated an ester showing the better lubricity provided the higher cutting performance. The turning tests of some stainless steels categorized as a difficult-to-cut material also demonstrated that MQL machining could improve the tool life and, in the range of low cutting speeds, could decrease the cutting resistance. Further, MQL end-milling of an aluminum alloy presented superior surface finish roughness to that obtained by dry and air blow end-milling operations.3. Influences of adsorption characteristics on the lubricating behavior of estersThe investigation regarding the adsorption behavior of various gases onto nascent metal surfaces verified that the adsorbing action of oxygen is most dominant and, if oxygen and an ester existed together, the lubricating film formed by their adsorption could reveal the action resulted from both the oxide and a part derived from the ester. sing a controlled atmospheres cutting apparatus, In addition, the adsorption of oxygen provided a preferable influence on cutting steel, whereas it caused low performance when cutting aluminum alloy.