Determination of Extreme Pressure and Anti-wear Properties of Lubricating Oil

Determination of Extreme Pressure and Anti-wear Properties of Lubricating Oil

Overview
  As essential lubricating media for mechanical equipment, lubricating oil forms protective oil films on friction pairs to reduce metallic wear and prevent oxidative corrosion. Classified into industrial oil, automotive oil and lubricating grease per service conditions, its extreme pressure and anti-wear performance directly impacts equipment service life. Under heavy-load conditions, broken oil film may cause metal sintering and mechanical seizure, hence national standards mandate regular physical and chemical testing of lubricants.

Test Purpose
  Determine four core indicators including last non-seizure load (PB), weld load (PD), mean Hertz load (ZMZ) and friction coefficient to evaluate load-bearing and anti-wear capacity for heavy-duty application. Tests comply with GB/T12583-98, GB3142-82, SH/T0189-92 and ASTM D5183-2005, using SH120 automatic four-ball friction and wear tester.

Test Samples & Instruments

Sample: Industrial lubricating oil / grease
Equipment: SH120 automatic four-ball tester, Φ12.7mm standard steel balls, high/normal-temperature oil cups and cleaning accessories.

Test Procedures
1. Fix three standard steel balls inside the oil cup and clamp one single ball onto the spindle taper hole; submerge contact points with test oil.
2. Power on tester and connected computer, launch control software, select corresponding standard test mode (PB/PD/friction coefficient), set load, spindle speed, test duration and temperature parameters.
3. Preheat equipment for 15 minutes, lift loading piston to reset readings of friction force, test load and timing; adjust temperature to preset value via temperature control module.
4. Start test; the spindle drives the upper ball to rotate for point-contact sliding friction. The system collects real-time friction and temperature data and plots relevant variation curves automatically.
5. Auto-stop upon test completion, unload piston, take out oil cup and measure wear scar diameter under microscope for parameter calculation.

Data Analysis & Conclusion
  Step-load testing is conducted in accordance with standard specifications. For qualified oil specimens, intact lubricating film and stable friction coefficient are maintained during graded loading, with PB=1220N and PD=2450N. After 60min test under 392N load and 1450r/min, average wear scar diameter is 0.39mm and ZMZ reaches 35.0N, meeting technical requirements for heavy machinery lubrication. In contrast, inferior lubricants feature poor load resistance, low PB & PD values, oversized wear scars and fluctuating friction, which will significantly accelerate component abrasion in practical operation.