CLADDING TECHNOLOGY SHANXI CO., LTDEffects of Different Treatment Processes on Microstructure and Wear Resistance of High-Alloy Weld Overlay Deposits
Literature Overview
This study investigates how various post-weld treatment processes influence the microstructural evolution and tribological performance of high-alloy weld overlay deposits. The research is particularly relevant for engineers working on severe-service components such as mining equipment, cement mill liners, and coal-handling machinery where wear resistance is the primary design criterion. The study compares multiple treatment routes including solution heat treatment, aging, stress relief, and combined treatments on high-alloy Fe-Cr-C-Ni system overlays deposited via submerged arc welding and plasma transferred arc methods.
Core Technical Findings
The study demonstrates that post-deposition thermal treatments significantly alter the carbide morphology, matrix hardness distribution, and overall wear resistance of high-alloy overlay systems. Without treatment, as-deposited overlays typically exhibit a heterogeneous microstructure with coarse primary carbides, retained austenite in Ni-rich systems, and significant residual stresses from the welding thermal cycle.
Key Treatment Routes Evaluated
| Treatment Process | Temperature (°C) | Duration (h) | Cooling Method | Primary Effect |
|---|---|---|---|---|
| As-deposited (no treatment) | — | — | — | Baseline reference |
| Solution heat treatment | 1050–1150 | 1–2 | Air cool | Dissolve secondary carbides, homogenize |
| Aging (precipitation) | 750–850 | 4–8 | Air cool | Precipitate fine M7C3/M23C6 carbides |
| Stress relief | 550–650 | 2–4 | Furnace cool | Reduce residual stress, minimal microstructure change |
| Solution + Aging | 1050 then 800 | 1 then 6 | Air cool | Optimal carbide dispersion and matrix strengthening |
| Multi-step aging | 800 + 650 | 4 then 4 | Air cool | Refine carbide distribution, reduce retained austenite |
Microstructural Evolution
The as-deposited condition typically shows a dendritic or cellular microstructure with primary carbides (M7C3 or M23C6 depending on Cr content) forming at dendrite boundaries. For Fe-Cr-C-Ni systems with 12–16% Cr and 3–5% Ni, retained austenite volumes of 15–30% are common in the as-welded condition, which paradoxically can enhance toughness but reduce hardness and wear resistance.
Solution heat treatment at 1050–1150 °C dissolves most of the secondary carbides and partially dissolves primary carbides, creating a supersaturated solid solution. Subsequent aging at 750–850 °C promotes controlled precipitation of fine, uniformly distributed carbides that provide superior wear resistance compared to the coarse primary carbide network in the as-deposited condition.
Wear Mechanism Analysis
The study identifies three primary wear mechanisms in these overlay systems:
- Adhesive wear — dominant in the as-deposited condition where soft matrix phases between hard carbides undergo plastic deformation and material transfer.
- Abrasive wear — reduced after proper heat treatment due to increased carbide volume fraction and improved carbide-matrix bonding.
- Fatigue wear — controlled by residual stress levels; stress relief treatments significantly reduce subsurface crack initiation.
Dry sliding wear tests against alumina (Al2O3) counterfaces at 10 N normal load, 0.2 m/s sliding velocity, and 1000 m sliding distance showed that the solution-treated plus aged condition achieved a specific wear rate of 2.3 × 10⁻⁶ mm³/N·m, representing a 45–60% reduction compared to the as-deposited condition (5.1 × 10⁻⁶ mm³/N·m).
Engineering Practice Implications
For production environments, the key insight is that post-weld treatment is not optional for high-alloy overlays intended for severe wear service. The minimum recommended treatment for Fe-Cr-C-Ni overlays (12–16% Cr, 3–5% Ni, 2–4% C) is solution heat treatment at 1100 °C for 1.5 hours followed by aging at 800 °C for 6 hours with air cooling. This provides the best balance between wear resistance and process practicality.
However, engineers must be mindful of distortion risks for thin-walled components and the potential for carbide network formation at grain boundaries during slow cooling from solution treatment temperatures. For thick deposits (>6 mm), furnace cooling rates of 50–80 °C/h from the solution temperature are recommended to minimize cracking susceptibility.
Study Insights and Reflections
This research reinforces the principle that weld overlay performance is determined not only by the consumable chemistry but also critically by the post-deposition processing. In my experience with field failures on mining conveyors and crushers, many premature overlay failures can be traced to inadequate or absent post-weld heat treatment. The study provides quantitative justification for implementing controlled thermal treatment protocols in welding procedure specifications (WPS) for high-alloy overlay applications, moving beyond the common industry practice of treating overlay deposits as "as-welded only" components.