ASTM D2625-20 Standard Test Method for Durability (Wear) Life and Load-Carrying Capacity of Solid Film Lubricants (Falex Pin and V Method)

The standard “ASTM D2625-20 Standard test method for durability (wear) life and load carrying capacity of solid film lubricants (Falex Pin and V method)” published by the American Society for Testing and Materials (ASTM) describes a test method for determining the durability (wear) life and load carrying capacity of dry solid film lubricants in steel-to-steel sliding applications.

This standard is based on the Coordinating Research Council, Inc. Report No. 419 “Development of a research technique for measuring the wear life of bonded solid lubricant coatings for airframes using the Falex tester.” Additionally, an SAE aviation standard, “AS 5272F Lubricant, solid film, heat-hardened, corrosion inhibitor, supply specification,” applies.

For the purposes of this standard, the following terms and definitions apply:

Dry solid film lubricants are dry coatings consisting of lubricating powders in a solid matrix bonded to one or both surfaces to be lubricated. expresses.
Direct load refers to the linearly applied load corrected to the 3550 N gauge reference or 13 300 N gauge reference bisecting the angle of the V block. This load is equivalent to the actual load times cos 42 degrees.
Durability (wear) life expresses the length of the test period (in minutes) before failure under a constant load condition, during which the applied test lubricant performs its function.
The gauge load refers to the value obtained from the gauge during the test run after correction to the standard curve using the calibration procedure for the reference gauge of 20 000 N. The gauge reading is independent of the particular gauge used and corrections are made by comparison with the Brinell ball impression diameters on a standard reference copper test coupon having a Rockwell hardness range of HB 37 to HB 39. An electronic calibration device is available to replace the copper coupon.
Load carrying capacity refers to the highest specified load sustained for at least 1 minute.

The endurance test (Procedure A) consists of running two stationary steel V-block specimens loaded to a predetermined value against a rotating steel pin specimen. Endurance (wear) life is determined when the torque increases by 1,13 N m.

The load-carrying capacity test (Procedure B) consists of running two stationary steel V-block specimens onto a rotating steel pin, increasing the load on the pin until a sharp increase in steady-state torque (1,13 N m) or pin fracture is experienced. Before both tests, a solid film lubricant is deposited on the surfaces of the test specimens.

This test method distinguishes between bonded solid film lubricants in terms of their wear life and load carrying capacity. If the test conditions are changed, the wear life may vary and the relative ratings of bonded solid film lubricants may differ.

Before starting the tests, the jaw supports for the V-blocks and test pins are thoroughly cleaned with a solvent that complies with this standard to remove any residue or oil from previous test runs. It is necessary to avoid contact with the mating surfaces of the V-blocks and test pins with fingers. Atmospheric contamination such as cigarette smoke should be avoided as this may adversely affect the test results.

The Falex Pin and V block testing machine to be used in the tests is shown in the figures given in the standard.

The load gauge is a device that measures in a 20.000 N range or a 13.300 N direct reading. A 3550 N direct reading load gauge can be used for Procedure A, but it does not have a sufficiently high load range for Procedure B. The primary figures for loads are shown for the 20.000 N gauge. Equivalent readings from the 3550 N or 13.300 N direct reading gauges can be obtained from the curve in the figure. An automatic cut-off, torque recorder, and timer can be used instead of the standard torque gauge (optional).

The equipment required for load cell calibration includes:

Standard test coupon: soft annealed copper HB 37/39
Allen screw: with 10 mm Brinell ball attached
Spare plug
Brinell microscope or equivalent
Ruler: steel, 150 mm long
Timer: graduated in minutes and seconds

Equipment required to apply dry solid film lubricants includes:

Desiccant for storing test pieces (the bottom of the desiccant should be filled with desiccant to maintain approximately 50 percent relative humidity, not necessary if the pieces can be stored in a smoke-free room at 50 percent plus/minus 5 percent relative humidity)
Forced circulation oven that can maintain a temperature of 149 degrees plus/minus 5 degrees
Single ball anvil micrometer reading 0 mm to 25 mm plus/minus 0,0025 mm
Appropriate equipment for preparation and application of solid film lubricant

Briefly, with this test method, the durability (wear) life and load carrying capacity of dry solid film lubricants in steel-to-steel sliding applications are determined.

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