ASTM D6425 Friction and Wear Properties of Extreme Pressure (EP) Lubricating Oils
ASTM D6425 Standard Test Method for Measuring Friction and Wear Properties of Extreme Pressure (EP) Lubricating Oils Using SRV Test Machine
9. Procedure
9.1 Installation of the Test Pieces and Lubricating Oil Specimen in the Test Chamber:
9.1.1 Using solvent resistant gloves, clean the test ball, ball holder, and disk by wiping the surfaces with laboratory tissue soaked with cleaning solvent (a mixture of equal volumes of n-heptane, isopropanol, and toluene. (Warning - This mixture is flammable and a health hazard.) Repeat wiping until no dark residue appears on the tissue. Immerse the ball and disk in a beaker of the cleaning solvent under ultrasonic vibration (if available) for 10 min. Dry the ball holder. Dry the test ball and disk with a clean tissue, ensuring that no streaking occurs on the surface.
9.1.2 Ensure that the machine is unloaded (indicated by a load reading of -13 or -14 N), and install the ball holder (upper specimen holder).
9.1.3 Place 0.03 mL of the lubricating oil to be tested on the cleaned disk. Then install the disk (place on the block). Tighten the fastening screw until resistance just begins.
9.1.4 Place the cleaned ball, using the tweezers, in the disassembled, cleaned, and dried ball holder. Tighten the fastening screw until resistance just begins.
9.1.5 Install the ball holder, and test ball in the test chamber.
9.1.6 Turn on the heater control, and preheat the disk holder to 50°C.
9.1.7 Apply a load of 50 N, loosen the fastening screws on both disk and ball holders, and then immediately tighten them with a torque wrench to 2.2 to 2.5 nm.
9.2 Test Run:
9.2.1 Start of the Test Run:
9.2.1.1 Allow 10 min for the test pieces and reference oil to reach and stabilize at the test temperature of 50°C.
9.2.1.2 When the temperature has stabilized, turn on the chart recorder paper feed (or the computer) and lower the recording pens. Depress the drive start toggle switch until the timer begins to count and then adjust the stroke amplitude knob to 1.00 mm.
9.2.1.3 When the digital timer reaches 30 s, increase the load to 300 N and run at that load for 2 h +/- 15 s.
9.2.2 Terminating the Test Run:
9.2.2.1 The test is automatically terminated by the timer when the preset test time has elapsed. The machine will automatically stop.
NOTE 9 - Power automatically turns off at the end of the test.
NOTE 10 - If, due to seizure, the friction coefficient exceeds the limit f = 0.35, the test should be terminated. If the machine does not automatically shut down at this point, it may have to be switched off manually.
9.2.2.2 At the end of the test, turn off the heater control, turn power back on, and reduce the load to -13 or -14 N for disassembly.
9.2.2.3 Remove and clean the test ball and disk in accordance with 9.1.1.
9.3 Evaluation:
9.3.1 Place the cleaned test ball on a suitable holder, and using a microscope, measure to the nearest 0.01 mm the scar width in the direction of sliding (d1) and again at 90° to the direction of sliding (d2). The mean wear scar diameter (WSD) is the average of these two measurements (WSD = (d1 + d2)/2).
9.3.2 Although not specifically part of the procedure, when additional wear analysis is required, perform a profilometric trace across the wear scar on the test disk in accordance with the profilometer manufacturer's instructions.
9.3.3 Measure the minimum and maximum coefficients of friction (fmin, fmax) and the coefficients at 15, 30, 90, and 120 min (f15, f30, f90, f120) from the chart recorder graph or computer, with a precision of 0.001.
9.3.4 If strong fluctuations (band width not less than 0.005) in the coefficient of friction are indicated on the chart recorder or other output device adjacent to the point at which the coefficient is measured, record the mean value and the magnitude of the fluctuations at that point (see Fig. 5).
