Standard Test Method for Wear Preventive (AW) Characteristics of Lubricating Fluid – Four-Ball Method (ASTM D4172)
The Four-Ball Wear Test (ASTM D4172) is used to evaluate the anti-wear (AW) properties of lubricating fluids, including oils and greases. This test measures the ability of a lubricant to reduce wear under constant load, speed, and temperature conditions.
1️⃣ Relevant Test Standard
| Test Method | Standard | Application |
|---|---|---|
| Four-Ball Wear Test | ASTM D4172 | Evaluates anti-wear (AW) performance of lubricating fluids |
| Four-Ball EP Test | ASTM D2596 | Determines extreme pressure (EP) properties |
| ISO Equivalent | ISO 20623 | International equivalent for EP/AW testing |
📌 ASTM D4172 is specifically for evaluating wear preventive properties, while ASTM D2596 is for extreme pressure (EP) properties.
2️⃣ ASTM D4172 – Test Procedure
🔹 Principle
✔ A rotating steel ball is pressed against three fixed steel balls immersed in the test lubricant.
✔ The balls rotate under a constant load (40 kgf), speed (1200 rpm), and temperature (75°C or 150°C) for 60 minutes.
✔ After the test, the wear scar diameter (WSD) on the three fixed balls is measured in millimeters.
🔹 Required Equipment
✅ Four-Ball Wear Tester (ASTM D4172 compliant)
✅ Steel Test Balls (12.7 mm, AISI 52100, HRC 64-66)
✅ Temperature Control System (for 75°C & 150°C tests)
✅ Microscope or Optical Measurement System
3️⃣ Key Test Parameters & Procedure
1️⃣ Sample Preparation
- The lubricant sample is placed in the test cup, fully submerging the steel balls.
2️⃣ Test Conditions
- Load: 40 kgf (392 N)
- Speed: 1200 rpm
- Temperature: 75°C (Standard) / 150°C (High-Temp Test)
- Test Duration: 60 minutes
3️⃣ Wear Scar Measurement
- The diameter of the wear scar (WSD) on the three lower balls is measured using an optical microscope.
4️⃣ Interpretation of Results
| Wear Scar Diameter (WSD, mm) | Lubricant Performance | Application Suitability |
|---|---|---|
| 0.30 – 0.40 mm | Excellent AW performance | High-quality hydraulic, turbine, and engine oils |
| 0.40 – 0.50 mm | Good AW performance | Industrial gear oils, moderate-duty lubricants |
| 0.50 – 0.60 mm | Moderate AW performance | General-purpose lubricating oils |
| > 0.60 mm | Poor AW protection | May lead to increased wear and component failure |
✔ Lower WSD = Better anti-wear performance
✔ Higher WSD = Poor wear prevention, risk of equipment failure
5️⃣ Applications of the Four-Ball Wear Test
| Industry | Purpose of Testing | Example Lubricant Applications |
|---|---|---|
| Automotive | Ensures minimal engine wear | Engine oils, transmission fluids |
| Industrial | Reduces gear & bearing wear | Hydraulic & gear oils |
| Aerospace | Prevents metal-to-metal wear in extreme conditions | High-performance turbine oils |
| Metalworking | Optimizes cutting & machining lubrication | Metalworking fluids & cutting oils |
📌 This test is widely used for selecting and formulating lubricants with superior anti-wear properties.
6️⃣ Choosing the Right Four-Ball Test Based on Lubricant Function
| Lubricant Type | Test Standard | Purpose |
|---|---|---|
| Engine & Gear Oils | ASTM D4172 | Evaluates anti-wear properties |
| Hydraulic & Turbine Oils | ASTM D4172 | Measures wear prevention |
| Greases & Heavy-Duty EP Oils | ASTM D2596 | Determines extreme pressure capability |
| Cutting & Metalworking Fluids | ASTM D4172 | Checks lubrication efficiency |
📌 ASTM D4172 focuses on wear prevention, while ASTM D2596 evaluates high-load EP protection.
Lubricant Types for Wear Preventive Testing (ASTM D4172 – Four-Ball Method)
Different lubricants have varied anti-wear (AW) performance requirements, depending on their application. The Four-Ball Wear Test (ASTM D4172) is commonly used for oils and fluids, rather than greases, to measure wear-preventive characteristics under moderate loads.
1️⃣ Lubricant Types Suitable for ASTM D4172 Testing
| Lubricant Type | Common Application | AW Testing Purpose |
|---|---|---|
| Engine Oils (SAE 0W-20, 10W-40, etc.) | Automotive, heavy-duty engines | Reduces wear in pistons, bearings & cams |
| Hydraulic Oils (ISO VG 32, 46, 68) | Industrial, mobile hydraulic systems | Prevents pump & valve wear |
| Gear Oils (GL-4, GL-5, ISO 150, 220, 320) | Automotive & industrial gearboxes | Minimizes wear in gears under sliding conditions |
| Compressor Oils | Air & gas compressors | Protects against wear in piston/cylinder contact areas |
| Turbine Oils | Power plants, steam/gas turbines | Ensures long service life by reducing wear |
| Transformer & Insulating Oils | Electrical power systems | Prevents wear in switches & contacts |
| Cutting & Metalworking Fluids | CNC machining, grinding | Enhances lubrication & tool life |
| Circulating Oils | Bearings & rotating machinery | Ensures smooth operation & reduces wear |
| Transmission Fluids (ATF, CVT, DCTF) | Automatic/manual transmissions | Protects clutch packs & planetary gears |
📌 Lower wear scar diameter (WSD) = Better anti-wear performance.
2️⃣ How to Select the Right Lubricant Type for Testing?
1️⃣ Determine the Application:
- Automotive (Engine, Gear, Transmission Oils) → Requires wear & friction testing.
- Industrial (Hydraulic, Turbine, Circulating Oils) → Focuses on long-term wear prevention.
- Metalworking Fluids → Needs lubrication and cooling properties.
2️⃣ Identify the Required Properties:
✔ Low-friction & wear-resistant additives (ZDDP, Boron, Molybdenum) improve AW performance.
✔ Viscosity matters – Higher viscosity lubricants generally provide better wear protection.
3️⃣ Choose the Right ASTM Test Method:
- ASTM D4172 → General anti-wear performance for oils.
- ASTM D5183 → Friction & wear analysis in boundary lubrication.
- ASTM D2266 → Grease wear testing under light loads.