Showing papers on "Tribometer published in 1986"

Tribological properties of MoNx coatings in contact with copper

Abstract: In metal forming processes, coatings can be used to prevent adhesion between the tool and the workpiece in order to increase the lifetime of the tool. A new promising coating material for copper forming tools is MoNx, which has low galling tendency in an unlubricated contact with copper. MoNx coatings were deposited in a magnetron sputtering system. Tribological tests were carried out in a pin‐on‐disk tribometer. Also the adhesion and structure of the coatings were characterized. The lowest coefficient of friction and the lowest wear rate against copper was measured when the nitrogen concentration in the coating was 15 at. %–18 at. % and the Vickers microhardness about 2000 HV at a load of 10 g.

A new chromium carbide‐based tribological coating for use to 900 °C with particular reference to the Stirling engine

Abstract: A new chromium carbide‐based coating (PS 200) is described. This coating is shown to have good friction and wear properties over a wide temperature range. A nickel alloy‐bonded chromium carbide coating was used as a baseline material for comparison with experimental formulated coatings. Coatings were plasma sprayed onto metal disks, then diamond ground to a thickness of 0.025 cm. Friction and wear were determined using a pin on disk tribometer at temperatures from 25 to 900 °C in hydrogen, helium, and air. Pin materials included several metallic alloys and silicon carbide. It was found that appropriate additions of metallic silver and of barium fluoride/calcium fluoride eutectic to the baseline carbide composition significantly reduced friction coefficients while preserving, and in some cases, even enhancing wear resistance. The results of this study demonstrate that PS 200 is a promising coating composition to consider for high‐temperature aerospace and advanced heat engine applications. The excellent re...

Tribological Properties of Selected Polymeric Matrix Composites against Steel Surfaces

Abstract: A unique tri-pin-on-disc tribometer was used to determine the tribological properties of commercial polymeric bearing materials, comprising various nylons, a silica-filled ultra-high molecular weight polyethylene (UHMWPE) and polyurethane elastomers At moderate to heavy loads, coefficients of friction (μ) against dry and paraffin oil-lubricated steel were independent of normal force and are presented as a function of sliding speed Values of μ for all the test materials except UHMWPE were high without lubrication Fatigue (frictional) wear and abrasive (cutting) wear were determined using discs of steel gauze and abrasive paper, respectively Wear relationships are given, enabling comparisons to be made of fatigue wear on rough steel (gauze) in non-transfer film conditions, and of cutting wear on an abrasive counterface in transfer film conditions The wear tests largely endorsed manufacturers' recommendations regarding applications for the test materials Friction test results indicated, however, that some of the polyurethanes would be unsuitable as dry bearing materials The silica-filled UHMWPE proved outstanding, with low friction against unlubricated steel, good fatigue wear resistance and excellent abrasion resistance

Tribological Properties of Graphite-Fiber-Reinforced, Partially Fluorinated Polyimide Composites

Abstract: Graphite-fiber-reinforced polyimide (GFRPI) composites were formulated from three new partially fluorinated polyimides and three types of graphite fiber. Nine composites were molded into pins and evaluated in a pin-on-disk tribometer. Friction coefficients, wear rates, pin wear surface morphology, and transfer film formation were assessed at 25 and 300 C. Also assessed was the effect of sliding speed on friction. Wear was up to two orders of magnitude lower at 25 C and up to one order of magnitude lower at 300 C than with previously formulated NASA GFRPI composites.

How to evaluate solid lubricant films using a pin-on-disk tribometer

Abstract: Over the years, the author has evaluated and compared hundreds of solid lubricant films using a pin-on-disk tribometer. The intent of this paper is to describe to the reader experimental techniques and some of parameters that have been observed to be important for the evaluation and development of new solid lubricant films. Pin-on-disk tribometers will be described and discussed as will experimental methods for evaluating solid lubricant materials. Methods of preparing surfaces for the coating of the thin films and different methods for applying the films will be reviewed. Factors that affect solid lubricant performance will also be discussed. Two different macroscopic mechanisms of solid lubricant film wear exist. These will be characterized schematically, and methods of measuring wear will be examined.