STUDIES ON TRIBO-FATIGUE ADDITIVES FOR AUTOMOTIVE GEAR OILS

Tribo-fatigue, an important phenomenon, is influenced by the lubricant base oil and lubricant additives. There are many ~pecifications for automotive hypoid gear oils which specifies different levels of performance. These specifications do not stipulate any requirements with respect to fatigue performance of the lubricant. However, tribo-fatigue is recognised as an important parameter for understanding the better performance of the lubricants. . In view of this, a programme was undertaken to generate data on tribo-fatigue performance of Indian automotive gear oils and search for additives which can enhance the fatigue performance of these lubricants. This paper deals with the studies made, on one such boron additive on a rolling contact four ball fatigue tester and summarises the results obtained and assesses the influence of the additive on tribo-fatigue performance of formulated gear oils. Keywords: Tribo-fatigue, gear oils, additives, rolling contact, four ball machine

A Laboratory screening test for evaluation of load bearing capacity (LBC) OF automotive (API GL-4 TYPE) gear oils

In India and in a few other developing countries, about 80% of total auto-gear oils being used are of API GL-4 level or MIL-L-2105 type. TIlis specification prescribes CRC-L-19, high speed shock load rear axle and CRC-L-20, high torque low speed rear axle tests. The facility for L-19 test does not exist today where as the test facility for L-20 test is limited due to availability of few sets of test gears. The current trend for the use of API GL-4 type oils will continu'e in India. In view of requirement not qnly in India but in some other developing countries, a need is felt to generate this test facilities at low cost and time. The paper describes the test method for evaluation of load bearing capacity of GL-4 type oils and cal) be considered as a substitute for CRC-L-20 test. \ r- Key Words: Gear oil, evaluation, load bearing capacity, test method

A labroratory screening tests for evaluation of load bearing capacity (LBC) of automotive gear API GL-5 type oils

API GL-5 type automotive gear oils are being used all over the world confirming to the specifications MIL-L- 2105 E that prescribes the performance tests like CRC-L -33, CRC-L-37, CRC-L-42 and CRC-L-60. At present, in India both API GL-4 and GL-5 type oils are being used. The CRC-L-37 test determines the load carrying characteristics of gear lubricants in hypoicf'axles under high-speed low torque and low speed high torque conditions. This test, specified for GL-5 oils is only available in U.S.A., which is expensive and time consuming. In view of the difficulty as well as high cost involved, a need is felt to develo

Studies on Rolling Contact Fatigue Lives of EN31 Steel Balls

A study was made on the rolling contact fatigue lives of EN31 steel balls with a mineral oil and containing different types ':)f chemical compounds as additives using a rolling contact four ball tester. Also two commercial gear oils and "'0'0 formulated oils were evaluated in a 4-ball tester for their influence on rolling contact fatigue lives of EN31 ~eei balls. From the fatigue test data ,the mean test time to failure (MTTF) was determined, This paper summarises the results obtained and assesses the relative influence of chemical additives on the rolling fatigue lives Fatigue, lubricants, additives, gear oils, mean time to failure(MTTF), 4-ball machin

EFFECT OF BIOCIDES ON LUBRICITY PERFORMANCE OF METALWORKING FLUIDS (MWF)

It is well known that metalworking fluids (MWF)I coolants are susceptible to growth of wide range of micro-organism including bacteria, fungi, molds and yeast. These micro-organisms can have detrimental effects not only on the performance and life of MWF but also effect the operator's health and the environment. For controlling these organisms, various types of biocides are incorporated in the MWF formulations. They may influence the lubrication characteristics. To examine the. role of biocides in governing the behaviour of lubricants on the lubricity property, a series of biocides were studied for wearscar diameter (WSD) on the 4-ball machine at different time interval. It was observed that the rate at which they act, differ widely to each other with lubricity and the life of fluids. r. KEY WORDS: Metalworking Fluids, Lubricity, Wear, Biocides

DEVELOPMENT OF MULTIPURPOSE ENVIRONMENT FRIENDLY LUBRICATING GREASE

The paper reports the work carried on the development of multipurpose grease using vegetable oil and a by-product (residual oil). This includes formulations and relevant tribological performance parameters. The studies resulted in two potential candidates as multipurpose grease formulations

Tribo-Fatigue Studies On Synthetic Auto-Gear Oil Formulations

The influence of polyol esters, with and with out commercial gear oil additives, on rolling fatigue lives of EN31 steel balls was studied in a rolling contact fatigue tester. The fatigue lives obtained thus were compared with those obtained with Reference gear oil. The study reveals that commercial gear oil additives are synergistic with polyol esters in improving fatigue lives of EN31 steel balls

Tribo-Fatigue studies of Gear oils on a rolling contact 4-BALL machine

This work has evaluated the rolling contact fatigue lives of EN-31 steel balls with several gear oil formulations using a 4-ball tester under accelerated test conditions. From the fatigue data generated Weibull plots are made and rolling fatigue lives L1o, Lso, characteristic life r] are determined for all the gear oils. Theoretical estimation of lubricant film thickness at the contact of surfaces for each gear oils is made. An attempt was made to assess the influence of film thickness on fatigue lives of steel balls. KEYWORDS Rolling fatigue lives, gear oils, 4-ball machine, weibull plot, film thicknes

Friction and Wear Characteristics of Organic Thiophosphoro Derivatives- A Critical Appraisal

The friction- and wear-reducing characteristics of a number of oil soluble sulphurised and phosphosulphurised derivatives for automotive and industrial applications have been reviewed. A critical appraisal of the suggested causes and mechanism of friction reduction and anti wear characteristics has been made. A review of the investigations carried out so far indicates that the creation of in situ films of simple inorganic salts, such as molybdenum disulphide, iron sulphide or phosphates of low shear strength and lamellar structures, does not appear to be the primary cause of low friction and wear. The authors have, therefore, undertaken a programme to synthesise and study the chemistry and tribochemical reactions in relation to friction and wear characteristics of hydrocarbonsoluble thiophosphoro derivatives of alkyl phenol, alcohols and fatty esters, in order to establish relationships between the reactivity, chemical nature and crystal structure of films formed on rubbing surfaces, and antifriction and antiwear characteristics. Molybdenum salts of various phosphorothio derivatives of pentadecylphenol and lauryl oleate of specific structures have been synthesised, and the friction and wear properties of their blends in mineral oil base stock have been studied. It can be clearly inferred from the results that type of bonding between sulphur, phosphorus and molybdenum, and reactivity of these derivatives with rubbing surfaces, determine their frictionreducing and anti wear characteristics. Their reactivity with iron and the nature of films formed are under investigation. friction, wear, molybdenum sulphurised, thiophosphoro derivatives