This study deals with the evaluation of antiwear performance of the vegetable oils [soybean oil, corn oil, rapeseed oil, and sunflower oil] and their blends, containing varying amounts of acetone, and organic acids [oxalic acid, succinic acid, and adipic acid]. Four-ball tribometer was employed as the wear tester. Extensive optimization with respect to the test oil composition was performed in order to explore the conditions under which the test oil demonstrated superior antiwear performance. In all cases, the desired conditions were obtained under a narrow range of test oil composition. It was observed that under the constant applied load of 78 N, test duration of 1 h, and given oil viscosity, succinic acid was found to be the most effective antiwear additive, i.e., resulted in smaller wear scar diameter [WSD] among the employed acids in all the test oils. For example, at 0.02 wt % of the succinic acid loading, the relative wear [WSD_{acid-loaded oil} / WSD_{acid-free oil}] was found to be 0.53, 0.62, 0.65, and 0.67 for the soybean oil [vis., 35 cSt], corn oil [vis., 33 cSt], rapeseed oil [vis., 47 cSt], and sunflower oil [vis., 36 cSt], respectively. The values of of the relative wear obtained under similar conditions with the same oils in the presence of oxalic acid and adipic acid were on the higher side of those obtained with the succinic acid. Further work is in progress in order to formulate energy saving and high performance environmental friendly lubricants for a wide range of practical applications.

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Numerical analysis for mixed lubrication has been performed in order to investigate the lubrication characteristics of the sliding surface of the vane in a rotary compressor. The modified Reynolds equation and the elastic contact equation, considering the surface roughness, are solved as a coupled problem. Using this analysis, the lubrication characteristics of the sliding surface of the vane are investigated by parameter survey on the design parameters such as the vane-slot length and the clearance between the vane and vane-slot. It is found that the influences of the vane-slot length on the friction loss were larger than that of the clearance.

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The friction and wear properties of gray cast iron (FC250) specimens sliding against AISI 52100 steel ball were evaluated under the lubrication of PAO (poly-alpha-olefin), PAO+ZnDTP (1.5 mass% ZnDTP) and PAO+PN (amine salt of alkoxyl phosphate, 1.5 mass% PN) oils. The tests were conducted using an Optimol SRV reciprocating friction and wear tester at a normal load of 50 N, and sliding frequencies of 10, 20, 30, 40 and 50 Hz. The morphologies of the worn surfaces of the FC250 specimens were observed using a scanning electron microscope (SEM) with energy dispersion X-ray spectroscopy (EDS). In addition, the elemental compositions and chemical states of several typical elements on the worn surfaces of the FC250 specimens were examined by means of X-ray photoelectron spectroscopy (XPS). The results indicated that the PAO+PN lubricant exhibited higher wear-resistance and lower friction coefficients than pure PAO and the PAO+ZnDTP lubricants, and this was partly attributed to the tribo-chemical reaction between the lubricant and the sliding surfaces.

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In the present work, an offset-halves journal bearing with ID=65 mm, OD=85 mm, L=65 mm, Cm=200 μm and C=500 μm has been tested to access temperature rise while operating with oils namely, Mak 2T, Hydrol 68 and Mak Multigrade at loads varying from 100-600 N and speeds from 3000-4000 rpm at constant supply pressure. Flow rates for different conditions were measured directly and the temperature information on three circumferential planes across the width of bearing was collected. The results indicate that with increase in load at constant speed and with increase in speed at constant load, the circumferential temperature of bearing increases in both the lobes for all the oils. For lower lobe, maximum temperature rise in central plane of the bearing is observed as 31.4ºC for Mak Multigrade oil at 4000 rpm and 600 N and minimum temperature rise is observed as 20.9ºC for Mak 2T oil at 3000 rpm and 100 N. For upper lobe, maximum temperature rise in central plane of the bearing is found to be 16.8ºC for Mak Multigrade oil at 4000 rpm and 600 N and minimum temperature rise is found to be 9ºC for Mak 2T oil at 3000 rpm and 100 N. Across the width of bearing, temperature rise is highest for Mak Multigrade oil (17.9ºC at 4000 rpm, 600 N) and is lowest for Mak 2T oil (8.3ºC at 3000 rpm, 100 N). Hence under the chosen operating conditions (load up to 600 N and speed up to 4000 rpm) and the oils, it is appropriate to use Mak 2T oil so as to make the bearing run cool.

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Under conditions of boundary lubrication, there is direct contact and surface films such as metal oxides and organic contaminants are mechanically removed by mechanical contacts. This causes to form a chemically active nascent surface. It is essential to understand the reaction between lubricant additives and the nascent metal surface. In this research, the well known organic sulfides were selected as the model compounds of extreme pressure additives (EP additives). The catalytic effect of a nascent metal surface without thermal effect was studied using cutting method with a ceramic tip and the reaction was monitored with a quadrupole mass spectrometer. The main result is that the type of alkyl group and the number of sulfur atoms in the central chain (for instance, mono-sulfide or disulfide) have a strong influence on the adsorption and reaction of the sulfide compounds.

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