CLADDING TECHNOLOGY SHANXI CO., LTDTungsten Carbide Alloy Wear-Resistant Cladding of Single-Tooth Rollers
Literature Overview
This technical report, authored by Ban Jinming, Liu Hongbo, and Xiao Jingjin from Tangshan Xinde Boiler Group Co., Ltd. and published in 2007, addresses the specialized challenge of applying tungsten carbide (WC) alloy overlay to single-tooth rollers used in boiler and material handling equipment. The single-tooth roller is a critical component in rotary kilns, grate systems, and material conveying mechanisms where severe abrasion occurs. The study focuses on selecting appropriate welding consumables, optimizing process parameters, and ensuring long-term wear resistance of the cladding layer under harsh operating conditions.
Core Technical Content
The fundamental challenge in single-tooth roller cladding lies in the geometric complexity of the tooth profile and the extreme tribological demands placed upon it. Unlike flat surfaces or simple cylindrical geometries, single-tooth rollers require cladding to conform to sharp edges, concave grooves, and convex peaks simultaneously. The tungsten carbide alloy overlay must maintain its hardness (typically above 1400 HV) while being adequately bonded to the substrate steel without cracking at the interface.
Material Selection and Consumable Parameters
The selection of WC-based welding consumables is governed by several competing requirements: hardness retention after thermal cycling, resistance to thermal fatigue cracking, and adequate ductility at the dilution boundary. Common consumable types include nickel-matrix hardfacing alloys with 50-70% WC particles (such as Ni60 + WC composites), cobalt-based alloys with WC (Stellite-type), and iron-based alloys with high WC content.
| Parameter | Typical Specification | Rationale |
|---|---|---|
| Overlay hardness | 1400-1800 HV | Abrasion resistance in rotary kiln service |
| Dilution rate | 15-25% | Balance between hardness and toughness |
| Preheat temperature | 250-350°C | Reduce thermal stress and hydrogen cracking risk |
| Interpass temperature | ≤300°C | Control HAZ microstructure and residual stress |
| Post-weld treatment | 600°C × 2h or stress relief | Eliminate residual stresses |
| WC particle size | 5-50 μm | Fine particles for uniform hardness distribution |
Process Route Analysis
The recommended welding sequence for single-tooth roller cladding follows a systematic approach:
- Substrate preparation: The base steel (typically Q235 or Q345) is machined to final dimensions with a 1-2 mm machining allowance on the cladding surface. The tooth profile is ground clean and free of oxide scale.
- Transition layer deposition: A nickel-based or austenitic stainless steel layer (2-3 mm) is applied first to provide a ductile buffer between the brittle WC-containing hardfacing and the carbon steel substrate.
- Hardfacing layer application: The WC-containing alloy is deposited in 2-3 passes, each 2-3 mm thick, with controlled interpass temperatures.
- Post-weld machining: The final surface is machined to the required tooth profile geometry, removing any spatter or irregularities.
Defect Analysis and Countermeasures
The primary defects encountered in WC alloy cladding of geometrically complex components include:
- Cracking at the tooth root: Caused by high constraint and thermal stress concentration at concave angles. Mitigation includes increased preheat, reduced heat input per pass, and strategic weld sequencing to relieve stress progressively.
- Porosity in the overlay: Resulting from inadequate shielding or contamination of the WC particles. Using GTAW or plasma arc with high-purity argon shielding is recommended.
- Spalling of the hardfacing layer: Due to excessive dilution or improper transition layer design. Maintaining dilution below 25% and using a nickel-matrix transition layer are effective countermeasures.
Engineering Practice Implications
In practice, the single-tooth roller cladding process requires careful consideration of the roller's operational environment. In rotary kiln applications, rollers experience temperatures of 200-400°C with continuous abrasive contact from refractory materials. The cladding must therefore resist not only abrasion but also thermal cycling fatigue. The authors' approach of using a multi-layer strategy with a ductile transition layer is consistent with modern best practices and aligns with the principles outlined in AWS D10.9 and ISO 14272 for hardfacing applications.
Study Insights and Reflections
This 2007 publication represents an important practical contribution to the field of hardfacing technology in China's heavy equipment manufacturing sector. The systematic approach to consumable selection, process optimization, and defect prevention reflects a mature engineering methodology. The emphasis on the transition layer between the hardfacing and substrate is particularly noteworthy, as it addresses the fundamental metallurgical incompatibility between brittle carbide-containing overlays and ductile steel substrates. For modern practitioners, this work provides a solid foundation for understanding the principles that still govern WC alloy cladding today, even as advanced techniques such as laser cladding and plasma transferred arc (PTA) have expanded the available process options.