CLADDING TECHNOLOGY SHANXI CO., LTDEffect of Tempering Temperature on Wear Resistance of Clad Dies
Literature Overview
This 2013 study from Chongqing University, authored by Xu Wujiao, Ding Yongfeng, and Wang Pengcheng, investigates how tempering temperature influences the wear resistance of clad dies used in metal forming applications. Published in the journal "Metal Heat Treatment," the work addresses a practical problem encountered in die manufacturing: the balance between hardness retention and residual stress relief during post-weld heat treatment of clad surfaces. The research is particularly relevant to engineers working on tool and die applications where surface hardness must be maintained while ensuring the substrate retains adequate toughness.
Core Technical Findings
The study examines clad dies fabricated by welding overlay processes onto carbon steel substrates, with various tempering temperatures applied after welding. The key findings revolve around the relationship between tempering temperature, microstructural evolution, and resulting tribological performance.
At lower tempering temperatures (below 500°C), the clad layer retains high hardness due to the preservation of martensitic and carbide structures, but the substrate may suffer from excessive residual stress. At higher tempering temperatures (above 650°C), while residual stresses are effectively relieved, significant softening of the overlay layer occurs due to carbide coarsening and tempering softening effects.
| Tempering Temperature | Overlay Hardness (HRC) | Substrate Toughness | Wear Resistance | Residual Stress Level |
|---|---|---|---|---|
| 450°C | High (>55) | Moderate | Excellent | High |
| 550°C | Moderate-High (50-55) | Good | Good | Moderate |
| 600°C | Moderate (45-50) | Good | Moderate | Low |
| 650°C | Low-Moderate (<45) | Excellent | Poor | Very Low |
The optimal tempering window identified in the study falls between 500°C and 550°C, where a good compromise between overlay hardness retention and substrate stress relief is achieved.
Microstructural Analysis and Wear Mechanisms
The wear mechanisms observed in the study include adhesive wear at high hardness conditions, abrasive wear at moderate hardness, and severe plastic deformation at low hardness conditions. Metallographic examination revealed that carbide distribution and size are critical factors governing wear performance. At 550°C tempering, fine dispersed carbides remain stable, providing effective resistance to abrasive wear without excessive brittleness.
The study also highlights the importance of the bond line microstructure. Excessive tempering temperatures can lead to intergranular carbide precipitation at the weld interface, creating preferential wear paths and reducing the effective life of the clad die.
Engineering Practice Implications
For production environments, this research provides clear guidance on post-weld heat treatment parameters for clad dies. Engineers should consider:
- Process selection: For dies requiring maximum surface hardness, lower tempering temperatures (450-500°C) with controlled cooling rates are recommended, supplemented by stress-relief annealing of the substrate separately if possible.
- Inspection protocols: Hardness profiles across the full thickness should be measured after tempering to verify that the overlay layer maintains adequate hardness while the substrate achieves acceptable toughness.
- Service life prediction: Wear testing at the selected tempering temperature provides baseline data for estimating die life in specific forming applications.
Key Reflections and Study Insights
This study reinforces a fundamental principle in cladding technology: the heat treatment of clad components requires careful consideration of the thermal sensitivity of both the overlay and substrate materials. Unlike homogeneous components, clad dies present a thermal mismatch challenge where the overlay material and base material may have different optimal tempering temperatures. The engineering solution often involves selecting overlay alloys with lower thermal sensitivity, or implementing multi-stage heat treatment schedules that address each material zone separately.
The practical significance of this work extends beyond die manufacturing to any application where clad surfaces must undergo post-weld heat treatment, including pressure vessels with overlay cladding that require stress relief after fabrication. The tempering temperature window identified here serves as a useful reference point for process development in similar material systems.