CLADDING TECHNOLOGY SHANXI CO., LTDApplication of Cladding Technology in Cutting Teeth
Introduction and Technical Challenges
Cutting teeth, used extensively in mining, quarrying, and earthmoving equipment, are subjected to some of the most severe wear conditions encountered in industrial applications. These teeth experience a combination of abrasive wear from rock and soil, impact loading from penetration into hard material, and adhesive wear from friction against the working medium. The service life of cutting teeth directly impacts equipment productivity and operating costs, with each tooth replacement causing significant downtime. Weld cladding technology offers a proven solution to extend cutting tooth life by depositing wear-resistant overlay materials on critical surfaces. This study note examines the cladding approaches, material selection, and process optimization for cutting teeth applications.
Types of Cutting Teeth and Cladding Requirements
Different types of cutting teeth have different geometric configurations and loading conditions, which influence the cladding strategy:
| Tooth Type | Application | Primary Wear Mode | Cladding Area | Target Hardness |
|---|---|---|---|---|
| Single point tooth | Excavator buckets | Abrasion + Impact | Cutting edge, tip | 55–62 HRC |
| Trencher tooth | Pipeline trenching | Abrasion + Abrasion | Full cutting surface | 50–58 HRC |
| Ripper tooth | Dozer rippers | Impact + Abrasion | Cutting edge, sides | 50–55 HRC |
| Dragline tooth | Surface mining | Abrasion + Impact | Cutting edge | 55–60 HRC |
| Reclaimer tooth | Stockpile reclaiming | Abrasion | Full working surface | 45–55 HRC |
The key challenge in cutting tooth cladding is achieving high hardness on the cutting edge while maintaining sufficient toughness in the body to resist impact fracture. This requires a graded approach where the hardness transitions from the body material (typically 25–35 HRC) through a transition zone to the hard overlay (55–62 HRC).
Cladding Processes for Cutting Teeth
Submerged Arc Welding (SAW) Overlay
SAW is the most widely used process for cutting tooth cladding due to its high deposition rate, deep penetration, and excellent productivity. The process is typically performed in automated or semi-automated configurations.
| SAW Parameter | Typical Value | Effect on Performance |
|---|---|---|
| Flux type | Rutilic or basic | Basic flux for lower hydrogen |
| Wire composition | Cr-W or Cr-V hardfacing wire | Determines overlay hardness |
| Current | 350–500 A | Higher current → deeper penetration |
| Voltage | 28–35 V | Controls bead width |
| Travel speed | 200–400 mm/min | Higher speed → lower heat input |
| Heat input | 2.0–4.0 kJ/mm | Must be controlled for hardness |
| Number of passes | 2–4 | Multi-pass for thickness and hardness |
Gas Metal Arc Welding (GMAW) Overlay
GMAW is used for smaller teeth or for field repair applications where portability is required. The process offers good positional flexibility and moderate deposition rates.
| GMAW Parameter | Typical Value |
|---|---|
| Wire diameter | 1.2–1.6 mm |
| Shielding gas | CO₂ or Ar/CO₂ (80/20) |
| Current | 180–280 A |
| Voltage | 22–28 V |
| Travel speed | 150–300 mm/min |
| Wire feed speed | 4–8 m/min |
Hot-Wire TIG Overlay
Hot-wire TIG (also known as hot-wire plasma transfer arc or hot-wire arc welding) is increasingly used for high-quality cladding of cutting teeth, particularly for precision components. The process provides excellent control over heat input and dilution.
| Hot-Wire TIG Parameter | Typical Value |
|---|---|
| Base current (TIG) | 80–150 A |
| Hot wire current | 150–250 A |
| Wire feed speed | 3–8 m/min |
| Shielding gas | Argon or Ar/CO₂ |
| Travel speed | 100–300 mm/min |
| Heat input | 1.0–2.5 kJ/mm |
Material Selection for Cutting Tooth Cladding
The selection of cladding material depends on the specific wear conditions and the required balance of hardness and toughness:
| Cladding Material Type | Composition | Hardness (HRC) | Toughness | Application |
|---|---|---|---|---|
| Cr-Mn martensitic | Cr 12%, Mn 10%, C 1.0% | 50–55 | High | General purpose teeth |
| Cr-W martensitic | Cr 18%, W 8%, C 1.2% | 55–60 | Medium | High abrasion teeth |
| Cr-V martensitic | Cr 15%, V 3%, C 1.5% | 58–62 | Medium | Hard rock teeth |
| Ni-based (Stellite) | Co 60%, Cr 25%, W 7% | 40–48 | High | High-temperature teeth |
| Ni-Cr alloy | Ni 60%, Cr 20%, C 3.0% | 55–60 | Medium | Abrasive + impact |
Process Optimization and Defect Prevention
Dilution Control
Dilution from the base metal is the primary factor limiting the hardness of the top overlay layer. For cutting teeth made from carbon steel (typically 0.2–0.4% C), dilution reduces the effective carbon and alloy content of the overlay. The following strategies are employed to manage dilution:
- Multi-pass welding: The first pass accepts high dilution (30–50%), while subsequent passes achieve lower dilution (10–20%) as the previous layer provides a compatible substrate.
- Groove preparation: Machining V-grooves or U-grooves on the tooth surface increases the effective weld volume and reduces the proportion of base metal in the final weld.
- Wire feeding in SAW: Using a separate hardfacing wire fed into the arc (in addition to the consumable electrode) allows independent control of dilution.
Defect Prevention
| Defect | Cause | Prevention |
|---|---|---|
| Cracking | High carbon, excessive restraint, hydrogen | Preheat 150–250°C, control interpass <150°C |
| Spalling | Excessive hardness, poor bonding | Multi-pass, controlled heat input |
| Lack of fusion | Poor surface preparation, low heat input | Clean surface, increase heat input |
| Porosity | Moisture in flux/electrode | Bake electrodes, use dry flux |
| Hardness below spec | Excessive dilution, slow cooling | Increase passes, control heat input |
Engineering Practice: Case Study of Excavator Bucket Teeth
In a coal mining operation, excavator bucket teeth were experiencing replacement every 12–15 days due to abrasive wear from coal and rock. The teeth were made from 42CrMo steel with a base hardness of 30 HRC. The cladding solution applied was:
- Process: SAW overlay with flux-cored wire
- Wire composition: Cr 18%, W 6%, C 1.3% (Cr-W martensitic)
- Number of passes: 3 (build-up + 2 overlay passes)
- Total overlay thickness: 5 mm
- Achieved hardness: 58 HRC (after air cooling)
- Service life improvement: From 12 days to 55 days (4.6× improvement)
The key to success was the use of a pre-machined groove (6 mm wide, 3 mm deep) on the cutting edge, which reduced dilution in the final pass to below 15% and ensured the top layer achieved the target hardness. The overlay showed uniform wear with no evidence of spalling or cracking over the extended service period.
Key Reflections and Conclusions
The application of cladding technology to cutting teeth demonstrates that significant service life improvements can be achieved through rational material selection and process optimization. The critical factors are dilution control, heat input management, and the selection of a cladding composition that balances hardness with toughness for the specific loading conditions. The graded approach—where the hardness transitions from the base metal through a transition zone to the hard overlay—is essential for preventing brittle fracture under impact loading. For engineers specifying cladding solutions for mining equipment, the key insight is that the overlay system must be designed as an integrated whole, considering not only the overlay material properties but also the base metal compatibility, the process parameters, and the service environment. The most effective cladding solutions are those that are tailored to the specific application rather than applied as generic solutions.