CLADDING TECHNOLOGY SHANXI CO., LTDAnalysis of Factors Affecting the Wear Resistance of Overlay Weld Metal
Literature Overview and Research Context
This paper by Hu Yawei and Yin Yousheng from the School of Materials Science and Engineering at Shenyang University of Technology (2002), published in the Journal of Shenyang University of Technology, systematically examines the factors governing the wear resistance of weld overlay deposits. Wear-resistant overlay welding is one of the most widely applied surface engineering techniques in heavy industry, particularly in mining, cement, power generation, and construction machinery sectors. The overlay layer is designed to provide enhanced resistance against abrasive, adhesive, and erosive wear mechanisms while maintaining metallurgical bond strength with the base material. Understanding the multi-factorial nature of wear resistance is essential for optimizing overlay welding consumables, process parameters, and application-specific design.
Core Technical Findings
The study identifies and analyzes several key factors that influence the wear resistance of overlay weld metal, categorizing them into material-related factors, process-related factors, and service-related factors.
Material-Related Factors
The chemical composition of the overlay weld metal is the primary determinant of its wear resistance. The study emphasizes the following composition-related aspects:
- Carbon content: Higher carbon content promotes the formation of hard carbides (Cr₇C₃, Cr₃C, Cr₅C₃, WC, TiC, Mo₂C), which are the primary wear-resistant phases. However, excessive carbon (>2.5 wt%) can lead to the formation of brittle cementite (Fe₃C) networks, reducing toughness and increasing susceptibility to spalling.
- Chromium content: Chromium enhances the formation of stable chromium carbides and improves oxidation resistance. The optimal range for hardfacing applications is typically 8–20 wt% Cr, depending on the specific wear mechanism.
- Tungsten, Vanadium, and Molybdenum: These elements form extremely hard secondary carbides (WC, VC, Mo₂C) that significantly enhance abrasive wear resistance. Their combined effect is synergistic when properly balanced.
- Microstructure: The distribution, morphology, and volume fraction of carbides are critical. A uniform dispersion of fine carbides in a tough austenitic or martensitic matrix provides the best combination of wear resistance and fracture toughness.
Process-Related Factors
| Process Parameter | Effect on Microstructure | Effect on Wear Resistance |
|---|---|---|
| Welding current (higher) | Coarser grain structure, larger carbides | Moderate — can reduce hardness |
| Welding speed (higher) | Finer grain, reduced heat input | Generally improves wear resistance |
| Travel speed | Controls dilution rate | Lower dilution preserves overlay composition |
| Number of passes | Each pass partially re-melts the previous | Multi-pass improves homogeneity |
| Shielding gas composition | Affects oxidation and nitridation | Ar + 2% O₂ can promote controlled carbide formation |
| Preheating temperature | Reduces cracking tendency | Indirect effect on wear properties |
The study highlights that the dilution rate between the overlay layer and the base metal is a critical process-controlled parameter. For nickel-based and cobalt-based hardfacing alloys, dilution should be kept below 10–15% to maintain the designed carbide chemistry. For iron-based hardfacing alloys, dilution up to 20–25% is generally acceptable due to the broader composition window.
Service-Related Factors
The wear resistance of the overlay layer in actual service is influenced by:
- Wear mechanism: Abrasive (two-body or three-body), adhesive, erosive, or impact-abrasive — each mechanism requires a different microstructural design.
- Temperature: Elevated operating temperatures can soften the matrix, promote carbide coarsening, and accelerate oxidation, all of which reduce effective wear resistance.
- Impact loading: High impact stresses can cause plastic deformation of the matrix, leading to carbide pull-out and accelerated material removal.
Process Optimization Recommendations
Based on the analysis, the following process optimization guidelines are recommended for achieving maximum wear resistance in overlay weld deposits:
- Consumable selection: Match the hardfacing alloy system (iron-based, nickel-based, cobalt-based, or tungsten-carbide-filled) to the dominant wear mechanism and operating environment.
- Multi-pass welding: Apply at least 2–3 passes to achieve a homogeneous microstructure and minimize the influence of the base metal dilution.
- Heat input control: Use moderate to low heat input to promote fine carbide precipitation and a refined matrix structure.
- Post-weld heat treatment: For martensitic iron-based alloys, a tempering treatment at 400–550 °C can relieve residual stresses while maintaining adequate hardness (HRC 45–55). For austenitic alloys, no PWHT is typically required.
- Surface finishing: Machining or grinding the overlay surface to the specified profile ensures proper fit-up and reduces stress concentration at the surface.
Engineering Practice Integration
In practical applications, the wear resistance of overlay weld metal is validated through standardized testing methods including the ASTM G65 pin-on-disk test, ASTM G99 sand rubber wheel test, and the dry sand abrasion test. Typical performance data for common hardfacing alloys are summarized below:
| Alloy Type | Typical Hardness (HRC) | Dry Sand Abrasion Loss (mg) | Application Example |
|---|---|---|---|
| Iron-based (Cr-C) | 55–65 | 80–150 | Coal chutes, hoppers |
| Iron-based (Cr-C-B) | 55–65 | 60–120 | Crusher liners |
| Nickel-based (Ni-Cr) | 35–45 | 200–400 | High-temperature wear parts |
| Cobalt-based (Co-Cr) | 40–50 | 150–300 | Turbine blades, valves |
| WC-filled iron-based | 60–70 | 30–80 | Drill bits, nozzles |
The engineering value of this study lies in its systematic framework for evaluating and optimizing wear resistance, which can be directly applied to the selection and qualification of overlay welding procedures for specific service conditions.
Study Insights and Implications
The comprehensive analysis presented in this study provides a valuable reference for engineers involved in the design and qualification of wear-resistant overlay welding applications. The multi-factorial approach to wear resistance evaluation — considering material composition, microstructure, process parameters, and service conditions in an integrated manner — reflects the complexity of surface engineering problems in practice. Engineers should recognize that maximizing wear resistance alone is insufficient; a proper balance between hardness, toughness, and fatigue resistance must be achieved to ensure reliable in-service performance. The study also underscores the importance of weld procedure qualification and consumable specification control, as even minor deviations in composition or process parameters can significantly affect the final wear performance of the overlay deposit.