Numerical Simulation of Wear Resistance in Overlay Mold Considering Tempering Temperature

Literature Overview and Research Context

The 2012 study by Xu Wujiao, Ding Yongfeng, and Wang Pengcheng from Chongqing University, published in Jinshu Rechuli (Metal Heat Treatment), presents a computational approach to analyzing the wear resistance of overlay molds using the Archard wear model combined with finite element analysis in DEFORM-3D software. The research specifically examines how different tempering temperatures influence the wear behavior of overlay layers on intermediate shaft molds. This work is significant because it bridges the gap between metallurgical design and tribological performance prediction, offering engineers a computational tool for optimizing overlay mold design without relying solely on time-consuming and expensive physical wear testing.

Core Technical Approach and Findings

The researchers employed the Archard wear model — a classical empirical model that relates wear volume to applied load, sliding distance, and a material-specific wear coefficient — within the DEFORM-3D finite element framework. The simulation analyzed the wear depth of overlay molds subjected to different tempering temperatures. The key finding is presented in the following table:

The most important finding of this study is that the wear resistance of the overlay mold does not correlate directly with hardness. This is a counterintuitive result that challenges the common engineering assumption that higher hardness always translates to better wear resistance. At a tempering temperature of 500°C, the overlay mold achieved the minimum wear depth of 9.98 × 10⁻⁵ mm, indicating optimal wear performance despite potentially lower hardness compared to lower tempering temperatures.

Mechanism Analysis: Why Hardness Alone Does Not Determine Wear Resistance

The decoupling of wear resistance from hardness can be attributed to several metallurgical and tribological factors:

1. Microstructural evolution during tempering — As tempering temperature increases, the martensitic structure in the overlay layer undergoes progressive decomposition, transforming into tempered martensite, bainite, and eventually spheroidized carbide structures. Each of these microstructures offers different combinations of hardness, toughness, and wear resistance.
2. Residual stress modification — Tempering reduces the high tensile residual stresses present in as-welded overlay layers. Excessive residual stresses can promote crack initiation and propagation during wear, reducing the effective wear life even if hardness is high.
3. Toughness-hardness trade-off — At very high hardness levels (achieved at low tempering temperatures), the material may become brittle, leading to microcracking, chipping, and delamination under wear conditions. Moderate tempering at 500°C may produce an optimal balance where sufficient hardness is retained while toughness is improved, resulting in better overall wear performance.
4. Carbide morphology and distribution — The tempering temperature influences the size, shape, and distribution of carbide particles in the overlay. Optimally tempered conditions may produce fine, uniformly distributed carbides that provide effective wear resistance without the brittleness associated with coarse or clustered carbide structures.

Engineering Practice Implications

For engineers designing and specifying overlay molds — particularly intermediate shaft molds used in rolling mills, forging operations, and extrusion processes — this study provides critical guidance:

• Do not assume that maximum hardness yields maximum wear life. The optimal tempering temperature must be determined through a combination of computational analysis and experimental validation, taking into account the specific loading conditions and wear mechanisms involved.
• 500°C tempering represents a promising condition for overlay molds requiring excellent wear resistance, but this should be validated against the specific service conditions, including contact pressure, sliding speed, temperature, and the nature of the counterface material.
• Numerical simulation offers a valuable screening tool for identifying optimal process parameters before committing to physical testing. The Archard model, while empirical, provides a reasonable approximation of wear behavior for many metallic systems and can significantly reduce the number of physical trials required.

The following decision framework can be applied when optimizing overlay mold tempering:

1. Define service conditions — Determine the primary wear mechanism (abrasive, adhesive, fatigue, or erosive), contact pressures, temperatures, and sliding distances.
2. Select overlay material — Choose an alloy system that provides the necessary combination of hardness, toughness, and thermal stability.
3. Perform computational wear analysis — Use finite element simulation with appropriate wear models to screen tempering temperatures.
4. Validate with physical testing — Conduct bench-scale or full-scale wear tests at the predicted optimal tempering conditions.
5. Implement and monitor — Apply the optimized tempering process and monitor wear performance in service, feeding back data for continuous improvement.

Reflections and Study Insights

This study exemplifies the growing importance of computational methods in welding and materials engineering. The integration of the Archard wear model with DEFORM-3D finite element analysis provides a practical framework for predicting wear behavior without relying exclusively on physical testing. While the Archard model has known limitations — it assumes uniform contact pressure, does not account for work hardening, and is sensitive to the empirical wear coefficient — it remains a widely used and reasonably accurate tool for comparative analysis.

The finding that wear resistance does not correlate with hardness is a reminder that engineering performance is governed by the interplay of multiple material properties, not by any single parameter. Engineers who focus exclusively on maximizing hardness may inadvertently sacrifice toughness, thermal stability, or fatigue resistance, leading to premature failure through mechanisms other than simple material removal. The optimal tempering temperature of 500°C identified in this study represents a balanced condition where the overlay material achieves the best compromise between hardness and toughness for the specific wear conditions modeled.

For engineers involved in overlay mold design and specification, this research underscores the value of a systems-level approach to materials selection and process optimization. The computational methods demonstrated here offer a pathway to more efficient design cycles, reduced development costs, and improved reliability of overlay-welded components in demanding industrial applications.