The lubricant performance capability for aero propulsion drive systems is derived from the physical properties of the oil and the chemical attributes associated with the oil formulation. All properties, such as viscosity, pressure-viscosity coefficient and full-film traction coefficient are inherent properties of the lubricating fluid. Chemical attributes are critical for the formation of protective boundary lubricating films on the surfaces to prevent wear and scuffing. To assure performance and to provide needed information for engineering design, test methodologies for at least five oil properties or attributes are being addressed: (1) pressure-viscosity coefficient, (2) full-film traction coefficient, (3) scuffing resistance, (4) wear resistance, and (5) micropitting propensity. While viscosity versus temperature data are readily available, the above five properties or attributes must be measured under relevant conditions for aero propulsion hardware systems. This document (ARP6156) describes the test method for scuffing and wear resistance. It should be noted that the test method results are limited to the selected test conditions, which may not be representative of the broad scope of conditions encountered in service.
Rationale: ARP6156 serves to document the conditions and procedures required for the user of a WAM ball-on-disc test machine to run a standard protocol scuffing load capacity test. The continuous measurement of the traction coefficient provides insight into the anti-wear and extreme pressure properties of the lubricant. The WAM scuffing load stage is a report item in AS5780 and the measurement method is currently described in the appendix to determine if limits can be assigned for aviation turbine oil qualification. The SAE E-34 committee has made a recommendation for the test method to be documented as recommended practice.