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FRICTION AND WEAR MEASUREMENTS USING A MODIFIED MTM TRIBOMETER

IP.com Disclosure Number: IPCOM000009117D
Publication Date: 2002-Aug-07
Document File: 32 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database

Related People

E. Yamaguchi: INVENTOR

Abstract

Of the many tribometers that PCS Instruments designs and manufactures, the Mini-Traction Machine (MTM) measurement system is one of the most popular. The instrument was designed to make traction measurements with an optional pin-on-disk friction and wear attachment. According to the manufacturer, use of the optional friction and wear attachment would allow differentiation of the friction and wear performance of various lubricants. By our determination, we have found that this attachment offered by PCS Instruments does not perform as expected. Therefore, over the past year, we successfully made a modification to the MTM that allows us to obtain friction and wear data. The modification involved the use of a ball-on-disk tribocouple in the pin-on-disk mode of the MTM. The data obtained differentiates friction and wear between various lubricants. Results show that alkyl zinc dithiophosphate (ZnDTP) gives better wear performance than alkaryl ZnDTP, which gives better wear performance than base oil. We can differentiate the performance of the alkyl ZnDTP from the base oil at the 95% confidence level. The results of this work corroborate earlier results obtained with the Godfrey tribometer using ZnDTPs in the presence of carbon black. Thus we believe that the modified MTM measurement system described in this publication provides a reliable method for determining friction and wear data of various supplemental wear inhibitors.

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FRICTION AND WEAR MEASUREMENTS USING A MODIFIED MTM TRIBOMETER

SUMMARY

Of the many tribometers that PCS Instruments designs and manufactures, the Mini-Traction Machine (MTM) measurement system is one of the most popular.  The instrument was designed to make traction measurements with an optional pin-on-disk friction and wear attachment.  According to the manufacturer, use of the optional friction and wear attachment would allow differentiation of the friction and wear performance of various lubricants.  By our determination, we have found that this attachment offered by PCS Instruments does not perform as expected.  Therefore, over the past year, we successfully made a modification to the MTM that allows us to obtain friction and wear data.   The modification involved the use of a ball-on-disk tribocouple in the pin-on-disk mode of the MTM. The data obtained differentiates friction and wear between various lubricants.  Results show that alkyl zinc dithiophosphate (ZnDTP) gives better wear performance than alkaryl ZnDTP, which gives better wear performance than base oil.  We can differentiate the performance of the alkyl ZnDTP from the base oil at the 95% confidence level.  The results of this work corroborate earlier results obtained with the Godfrey tribometer using ZnDTPs in the presence of carbon black.  Thus we believe that the modified MTM measurement system described in this publication provides a reliable method for determining friction and wear data of various supplemental wear inhibitors.

INTRODUCTION

Lubricant suppliers are under increasing pressure to provide high quality lubricants with superior oxidation and wear performance.  In recent years, governmental regulations have required exhaust gas catalysts to reduce emissions of hydrocarbon and nitrogen oxides which are key components of smog.

Exhaust gas catalysts are sensitive to the types and levels of additives present in engine oil.  The next generation of motor oils may have significantly lower sulfur, phosphorus, and sulfated ash contents to ensure exhaust gas catalyst performance throughout the life of the engine.  However, phosphorus is a key component in commercial engine oils, used for both antiwear and oxidation inhibition.

Engine testing of new low sulfur, low phosphorus antiwear components is expensive and time consuming so bench testing of potential candidates is highly desirable as a first step evaluation.  First, one should develop a bench test that gives data that correlate to current engine test performance, i.e., GF-3 levels of phosphorus (0.1% P).  Then one can use the bench test to study low phosphorus-containing oils (0.05% P).

Sometime ago, we measured the relative wear performances of commercial ZnDTPs in a pin-on-disk Godfrey tribometer, with oils containing carbon black to simulate engine soot as part of a study on soot-induced wear.  The disk rotated parallel to the floor and the conditions of the test are given in Table 1.  In this publication, we compare the results of...