Block-on-Ring Wear Tester (ASTM D2714, ASTM G77)
A Block-on-Ring Wear Tester is used to evaluate the friction, wear resistance, and load-carrying capacity of lubricants, coatings, and materials under sliding contact conditions. It is commonly applied in lubricating oil, grease, metal coatings, and additive performance testing.
1. Key Applications
✅ Lubricant Testing: Evaluates the wear protection of engine oils, hydraulic oils, and greases.
✅ Additive Performance Testing: Measures anti-wear (AW) and extreme pressure (EP) properties of lubricants.
✅ Material Wear Analysis: Tests coatings, polymers, and metals for durability.
✅ Friction Testing: Determines the coefficient of friction (COF) under different loads.
2. Test Standards & Methods
| Test Standard | Application |
|---|---|
| ASTM D2714 | Wear and friction behavior of lubricants |
| ASTM G77 | Dry and lubricated wear testing of materials |
| ASTM D3704 | Wear and friction properties of lubricating greases |
| ASTM D4172 | Anti-wear performance of lubricants |
3. Test Principle & Setup
1️⃣ Test Configuration
- A rectangular block is pressed against a rotating steel ring under a fixed load.
- The wear track and friction force are monitored during the test.
2️⃣ Test Conditions
- Load: 50 N to 1000 N (adjustable)
- Speed: 100 to 1000 rpm
- Temperature: Room temperature or heated conditions (optional)
- Duration: 10 to 60 minutes
3️⃣ Measurements
✅ Wear Scar Width (mm): Determines wear rate
✅ Friction Coefficient (μ): Evaluates lubricant performance
✅ Weight Loss (mg): Quantifies material loss
4. Interpretation of Results
| Lubricant Type | Typical Wear Scar (mm) | Typical Coefficient of Friction (μ) |
|---|---|---|
| Engine Oil (SAE 10W-40, 5W-30) | 0.2 – 0.5 mm | 0.08 – 0.12 |
| Hydraulic Oil (ISO VG 46, 68) | 0.3 – 0.6 mm | 0.09 – 0.15 |
| Grease (NLGI 2, NLGI 3) | 0.1 – 0.4 mm | 0.06 – 0.1 |
| Industrial Gear Oil (EP Additives) | 0.2 – 0.5 mm | 0.08 – 0.12 |
🔹 Lower wear scar & lower friction coefficient = Better lubricant protection
🔹 High wear scar & high friction coefficient = Poor lubricant performance
5. Equipment Features to Consider
✔ Automatic Load Control: Adjusts applied force precisely.
✔ Real-Time Friction Monitoring: Graphs COF changes.
✔ Wear Measurement System: Optical or laser measurement.
✔ Variable Speed & Temperature Control: Simulates real-world conditions.
Methods for Determining Extreme Pressure (EP) Performance of Lubricating Fluids
Extreme Pressure (EP) performance testing evaluates a lubricant’s load-carrying capacity, anti-wear (AW) properties, and scuffing resistance under high-stress conditions. The most widely used methods include:
1. Common Test Standards & Methods
| Test Method | Standard | Purpose |
|---|---|---|
| Four-Ball EP Test | ASTM D2783, ASTM D2596 | Determines weld load, load-wear index |
| Timken OK Load Test | ASTM D2782 | Measures lubricant film strength under rolling contact |
| FZG Gear Test | ASTM D5182, DIN 51354 | Evaluates scuffing resistance in gears |
| SRV Friction & Wear Test | ASTM D5706, ASTM D5707 | Simulates high-pressure reciprocating wear |
| Falex Pin & Vee Block Test | ASTM D3233 | Tests lubricant performance under continuous sliding |
| Brugger Test | DIN 51347 | Determines high-pressure lubricity |
2. Four-Ball Extreme Pressure (EP) Test – ASTM D2783 / D2596
Principle
A rotating steel ball is pressed against three stationary balls under an increasing load until welding occurs. The test determines the lubricant’s load-carrying and anti-weld properties.
Test Conditions
- Load: 10 to 800 kg
- Speed: 1760 rpm
- Temperature: Ambient or controlled
- Duration: 10 seconds per load step
Key Parameters Measured
✅ Weld Load (kgf): The maximum load before the balls weld together.
✅ Load-Wear Index (LWI): Measures lubricant’s ability to prevent wear under increasing loads.
✅ Scar Diameter (mm): The wear mark on balls after test.
Typical Results for Different Lubricants
| Lubricant Type | Weld Load (kgf) | Load-Wear Index (LWI) |
|---|---|---|
| Low-EP Industrial Oil | 80 – 160 kgf | 20 – 40 |
| Automotive Gear Oil (GL-4) | 200 – 250 kgf | 30 – 60 |
| High-EP Gear Oil (GL-5) | 250 – 400 kgf | 60 – 100 |
| Heavy-Duty Grease (EP Additives) | 250 – 500 kgf | 80 – 120 |
🔹 Higher weld load & LWI = Better EP protection
🔹 Smaller wear scar = Less wear under pressure
3. Timken OK Load Test – ASTM D2782
Principle
A rotating steel roller is pressed against a stationary block with increasing load until scuffing occurs.
Test Conditions
- Load: 4 – 90 lbs (1.8 – 40 kg)
- Speed: 800 rpm
- Duration: 10 minutes
Key Parameter Measured
✅ OK Load (lbs): Maximum load before scoring occurs.
Example OK Load Values:
- Standard Industrial Oil: 10 – 20 lbs
- EP Gear Oil (GL-4): 30 – 40 lbs
- Heavy-Duty Gear Oil (GL-5): 50 – 70 lbs
- Extreme EP Grease: >70 lbs
🔹 Higher OK Load = Stronger EP Protection
4. FZG Gear Test – ASTM D5182 / DIN 51354
Principle
A geared transmission system is run under increasing loads to evaluate scuffing resistance.
Test Conditions
- Load Stages: 1 – 12
- Speed: 1450 rpm
- Temperature: 90 – 120°C
- Duration: >20 minutes per stage
Key Parameter Measured
✅ Failure Load Stage (FLS): The highest stage before scuffing occurs.
Typical Ratings:
- Low-EP Oil (FLS 4 – 6) → Standard industrial gear oils
- Medium-EP Oil (FLS 8 – 10) → GL-4 automotive gear oils
- High-EP Oil (FLS 10 – 12) → GL-5, synthetic heavy-duty oils
🔹 Higher FLS = Better gear protection
5. SRV Friction & Wear Test – ASTM D5706 / D5707
Principle
A reciprocating pin-on-disc system applies high loads to measure lubricant friction and wear properties.
Key Parameters Measured
✅ Coefficient of Friction (COF) → Lower values indicate better EP lubrication.
✅ Wear Volume (mm³) → Less wear indicates better protection.
Typical COF Values:
- Standard Oil: 0.12 – 0.18
- EP Gear Oil: 0.08 – 0.12
- High-EP Grease: 0.06 – 0.10
🔹 Lower COF & wear = Better EP performance
6. Conclusion: Choosing the Right Test
| Test Method | Best For | Measures |
|---|---|---|
| Four-Ball EP (ASTM D2783) | General EP testing | Weld load, LWI, wear scar |
| Timken OK Load (ASTM D2782) | Rolling contact EP performance | Max load before scoring |
| FZG Gear Test (ASTM D5182) | Gear oils, transmission fluids | Failure load stage (FLS) |
| SRV Friction Test (ASTM D5706) | High-pressure wear & friction | COF, wear volume |
| Falex Pin & Vee Block (ASTM D3233) | Continuous sliding wear | Load-carrying capacity |