V.K. Verma

A study of N, O and S heterocyclic compounds as extreme pressure lubricant additives

Abstract The potential EP activity of certain synthetized 2-arylamino-5-(4′-pyridyl)-1,3,4-oxadiazoles and 2-arylamino-5-(4′-pyridyl)-1,3,4-thiadiazoles has been evaluated using a four-ball lubricant testing machine. All of the additives were found to be effective at higher loads; however, 2-p-methoxyphenylamino-5-(4′-pyridyl)-1,3,4-oxadiazole and 2-p-chlorophenyl-amino-5-(4′-pyridyl)-1,3,4-oxadiazole have shown good activity. The surface topography of the bearing ball wear scars was studies using scanning electron microscopy and electron probe micro-analysis techniques.

The role of certain substituted 2-amino-benzothiazolylbenzoylthiocarbamides as additives in extreme pressure lubrication of steel bearing balls

Abstract Some 2-amino-benzothiazolylbenzoylthiocarbamides have been synthesized and evaluated for their extreme pressure additive activity in a four-ball machine. The test specimens were steel bearing balls and the parameters studied were wear-scar diameter, 2.5 s Seizure delay load, coefficient of friction, flash temperature parameter, mean specific pressure and mean Hertz load. The wear-scar surface was investigated by scanning electron microscopy and electron probe microanalysis techniques.

The load-carrying properties of certain S-alkylisothioamides and their effectiveness as extreme pressure lubricant additives

Abstract Certain S-alkylisothioamides were synthesized and their load-carrying capacities assessed using a Seta Shell four-ball machine. S-benzylisothiobenzamide was found to be potentially attractive.

1,3,4-Thiadiazoles as potential EP additives — a tribological evaluation using a four-ball test

Abstract This paper reports a comparative study of the wear-reducing efficiency and extreme pressure properties of 0.5% ( w v ) admixtures of paraffin oil and 2-amino-5-arylamino-1,3,4-thiadiazole additives and a commercial sulphur-phosphorus additive in a four-ball test. 2-Amino-5-p-Cl-phenylamino-1,3,4-thiadiazole additive shows excellent EP properties as is evident from the surface smoothness of SEM micrographs. The tribochemistry of the wear-scar surface has been investigated by the auger electron spectroscopy (AES) technique.

A study in EP activity evaluation of some new oil-soluble Mo-S complexes

Abstract 0.5% (w/v) solutions of bis(1,5-diaryl-2,4-dithiomalonamido) dioxomolybdenum complexes in paraffin oil were found to reduce significantly wear and friction of the steel balls in a four-ball test. The additive, bis(1,5-di-p-methoxyphenul-2,4-dithiomalonamido) dioxomolybdenum (VI) afforded higher values of initial seizure load (ISL, 112 kgf), 2.5 second seizure delay load (2.5 s SDL, 126 kgf), weld load (WL, >500 kgf), flash temperature parameter (FTP, 296) and mean Hertz load (MHL, 84 kgf) as compared with the plain paraffin oil and a sulphur-phosphorus additive. The tribological end effects were studied by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) techniques respectively.

Mechanism of ep additive-metal interaction: Assessment of certain S-benzylisothiocarbamides

Abstract The synthesis of certain S-benzylisothiocarbamides and the assessment of their extreme pressure (ep) properties are reported. These additives were compared with a commercial additive. The tribological end effects were studied using a scanning electron microscope. m-chlorophenyl and p-tolyl-S-benzylisothiocarbamides were found to be potentially effective. The mechanism of ep activity is discussed and a theory put forward to explain the ep additive-metal interaction.

EP activity evaluation of tris(N-arylthiosemicarbazido)molybdenum(III) on steel balls in a four-ball test

Abstract Admixtures of tris(N-arylthiosemicarbazido)molybdenum(III) in paraffin oil have been evaluated for their EP activity in a “four-ball test”. The additive, tris(N-p-methoxyphenylthiosemicarbazido)molybdenum(III), afforded higher values of ISL (1098 N), WL ( > 4900 N), MHL (745 N), FTP (188) and PWI (17) and lower values of wear-scar diameter and friction coefficient as compared with the paraffin oil and molybdenum disulphide additive. The topography and tribochemistry of the wear-scar surface have been studied by means of scanning electron microscopy and scanning Auger electron spectroscopy techniques, respectively.

The assessment of dithiocarbamates as extreme pressure lubricant additives

Abstract A number of aryl/alkyl-dithiocarbamates have been assessed as extreme pressure additives using a Seta-Shell four-ball lubricant testing machine. p-Tolyl dithiocarbamate and o-tolyl dithiocarbamate were found to be effective.

A study in the tribochemistry of alkyldithiobiurets and their MoS complexes as EP additives

Abstract 0.5% solutions of 1-alkyl-2,4-dithiobiuret ligands and their MoS complexes i.e. μ-hydroxo-μ-(1-alkyl-2,4-dithiobiureto)-bis-[dioxohydroxo molybdenum-(VI)] in paraffin oil were found to significally reduce wear and friction of 12.7 mm diameter steel balls in a four-ball test. In particular, the additive μ-hydroxo-μ-(1,1-dimethyl-2,4-dithiobiureto)-bis[dioxohydroxo-molybdenum-(VI)] was found to exhibit an appreciable increase in the load carrying capacity of the lubricant and a decrease in the values of coefficient of friction. The additive μ-hydroxo-μ-(1,1-dimethyl-2,4-dithiobiureto)-bis[dioxohydroxo-molybdenum(VI)] was also found to be effective at high speeds. The topography and tribochemistry of the used ball specimens were examined by means of scanning electron microscopy and scanning auger electron spectroscopy techniques, respectively.

EP activity evaluation of cyclic disulphides using ball bearings of different compositions

Abstract Employing a four-ball machine and using steel ball bearing specimens of 12.7 mm diameter, the potential EP activity of certain cyclic disulphide additives in liquid paraffin has been evaluated. The additive (3,5-di-p-Cl-phenylimino-1,2,4-dithiazolidine) has a comparatively good ISL value (100 kgf), higher values of weld load (> 500 kgf), mean Hertz load and FTP, and lower values of wear scar diameter and coefficient of friction. It appears to show excellent anti-friction properties and has been found to be effective with ball bearings of different compositions. The topography of the ball bearing surface was studied by using the technique of scanning electron microscopy.