Tungsten carbide bushings are known for their high 硬度 and long life. But they can still crack when the working conditions or installation steps are not correct.
Cracks reduce performance and may cause pump or machine failure. This guide explains the main reasons why these bushings crack and what you can do to avoid these problems.
Understanding Why Cracks Happen in Tungsten Carbide
Tungsten carbide is very hard, but also brittle. This means it can resist wear but cannot absorb strong impact or heavy stress.
When a bushing faces force it was not designed for, cracks can form, especially near edges or thin walls.
Key Characteristics That Influence Cracking
| Material Property | Influence on Cracking |
|---|---|
| 高硬度 | Strong wear resistance but low impact tolerance |
| 脆性 | Cracks form under sudden loads or shock |
| Thermal Sensitivity | Rapid temperature change increases stress |
| 粘合剂类型 | WC-Co and WC-Ni respond differently to corrosion and fatigue |
Root Cause: Improper Press-Fit Conditions
Press-fitting is a common installation method, but too much interference or uneven force can create high hoop stress in the bushing. This stress builds up and leads to cracks after installation or during operation.
1). Signs of Press-Fit Cracking
Cracks forming around the outer surface
Bushing becomes tight or distorted
Chipping at the edges
Sudden failure after startup
2). Common Press-Fit Mistakes
| Mistake | Effect |
|---|---|
| Too much interference fit | Excess stress on the bushing |
| Hammering instead of controlled pressing | Shock impact cracks |
| No lubrication during pressing | Uneven loading, scoring, cracking |
| Misalignment during press-fit | Bushing tilts and cracks at edges |
Root Cause: Misalignment Between Shaft and Housing
If the shaft is not centered inside the bushing, the load becomes uneven. One side carries more pressure, leading to bending stress and surface cracks.
1). Symptoms of Misalignment Cracking
Wear marks on only one side
Out-of-round wear pattern
Early vibration
Vertical or angled cracks along the bore
2). Typical Misalignment Sources
Shaft machining errors
Housing bore not perpendicular
Machine frame distortion
Bearing seat damage
Root Cause: Thermal Shock and Temperature Stress
Tungsten carbide does not expand as much as steel or cast iron. If temperature changes quickly, the bushing can crack from thermal shock.
This often happens in pumps running hot fluid or experiencing sudden cooling.
1). Temperature-Related Crack Conditions
Rapid cool-down from cold water during flushing
Running dry, then sudden cooling from fluid
Heating due to friction from poor lubrication
2). Recommended Thermal Limits
| 健康）状况 | Recommendation |
|---|---|
| Temperature rise | Keep steady, avoid fast spikes |
| Cooling | No rapid cold-water exposure |
| Dry-running heat | Stop equipment before temperature rises too high |
Root Cause: Corrosion and Binder Attack
Although tungsten carbide is stable, its binder metal (Co or Ni) is vulnerable in certain fluids.
If the binder corrodes, the structure weakens. Cracks then form under normal load because the material loses toughness.
1). Fluids That Increase Cracking Risk
High-chloride water
Acidic or low-pH fluids
Strong alkaline cleaners
Saltwater with high oxygen content
2). How Binder Attack Leads to Cracking
Corrosion begins at the binder.
Grain boundaries weaken.
Micro-cracks form.
Cracks grow under load.
Root Cause: Impact and Handling Damage
Tungsten carbide chips easily if dropped or hit. Many cracks start before the bushing is even installed due to poor handling during shipping, storage, or unpacking.
1). Common Handling Mistakes
Dropping the bushing on a hard surface
Allowing bushings to collide with each other
Using metal tools that strike the edges
Storing without padding
2). Early Crack Indicators
Small chips around the edge
Hairline cracks visible under magnification
Slight deformation at corners
How to Fix or Prevent Cracking in Tungsten Carbide Bushings
Preventing cracks begins with understanding how stress enters the bushing. Good installation, controlled operating conditions, and correct material selection solve most of the problems before they start.
Fixes and Preventive Actions
| 问题 | 解决方案 |
|---|---|
| Press-fit cracking | Use proper interference values and controlled pressing |
| Misalignment | Check shaft and housing geometry before assembly |
| Thermal shock | Control temperature changes and avoid dry running |
| Binder corrosion | Select WC-Ni or corrosion-resistant grades |
| Impact damage | Improve packaging and handling |
结论
Cracking is preventable when the right installation, handling, and operating controls are followed.
By understanding how stress, temperature, alignment, and corrosion affect tungsten carbide bushings, companies can extend service life and avoid costly failure.
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