CLADDING TECHNOLOGY SHANXI CO., LTDWear Resistance Study of Mining Pick Teeth Based on Plasma Cladding Technology
Literature Overview
This study focuses on applying plasma transferred arc (PTA) cladding technology to mining pick teeth, which are critical cutting tools used in coal mining and tunnel boring operations. The literature examines how plasma cladding can significantly improve the surface wear resistance of pick teeth compared to conventional manufacturing methods. Mining pick teeth are subjected to severe abrasive and impact loading conditions, making surface hardening and wear protection essential for extending service life and reducing operational costs.
Core Technical Content
The research investigates the plasma cladding process parameters, including arc current, travel speed, powder feed rate, and gas flow rate, and their influence on the cladding layer composition, microstructure, and wear resistance. The study typically employs high-chromium cast iron, carbide-containing alloys, or nickel-based alloy powders as cladding materials to achieve high hardness and abrasion resistance.
Key Process Parameters
| Parameter | Typical Range | Effect on Cladding Quality |
|---|---|---|
| Arc Current | 120–220 A | Controls dilution rate and dilution of base material into cladding |
| Travel Speed | 150–400 mm/min | Affects bead width, penetration, and cooling rate |
| Powder Feed Rate | 80–250 g/min | Determines deposition rate and cladding thickness |
| Shielding Gas Flow | 8–15 L/min | Prevents oxidation and porosity formation |
| Preheating Temperature | 150–300 °C | Reduces thermal cracking tendency in base material |
Microstructural Analysis
The cladding layer microstructure typically consists of a matrix of martensite or austenite with dispersed hard carbide particles such as M7C3, M2C, or MC type carbides. The base material, usually a low-carbon or medium-carbon steel, undergoes a heat-affected zone (HAZ) transformation resulting in a tempered martensite or bainite structure at the interface. The dilution rate is a critical factor that determines the final hardness of the cladding layer. When the dilution rate is controlled below 15%, the cladding layer can achieve hardness values exceeding 60 HRC, providing excellent wear resistance.
Wear Test Results
The wear resistance evaluation typically employs a pin-on-disk tribometer or a block-on-ring test simulating the actual working conditions of mining picks. The study demonstrates that plasma-cladded pick teeth exhibit 3–5 times longer service life compared to uncladded or conventionally hardened counterparts. The wear mechanism analysis reveals that the cladded surface transitions from adhesive wear at the beginning to abrasive wear as the hard carbide phase becomes dominant in resisting material removal.
Engineering Practice Integration
From an engineering perspective, several practical considerations emerge from this study. The base material of pick teeth often contains high carbon content, which poses a risk of excessive hardness in the HAZ leading to cold cracking during subsequent operations. Preheating and post-weld heat treatment become essential process steps. Additionally, the geometry of pick teeth presents challenges for automated cladding, requiring careful path planning to ensure uniform coverage on complex three-dimensional surfaces.
The study also highlights the importance of controlling the dilution rate. In practice, multi-pass cladding with varying powder compositions can be employed—a dilution-absorbing first pass followed by high-carbon or carbide-rich subsequent passes—to optimize both bonding strength and surface hardness. This approach aligns with the layered cladding philosophy commonly used in bimetal pressure vessel fabrication, where transition layers are designed to manage the metallurgical compatibility between dissimilar materials.
Key Questions and Reflections
One significant question arising from this study is the long-term performance of plasma-cladded pick teeth under cyclic impact loading, which is characteristic of actual mining conditions. While laboratory wear tests demonstrate excellent abrasion resistance, the resistance to fatigue spalling and chipping under repeated impact deserves further investigation. Another consideration is the economic viability—plasma cladding equipment requires significant capital investment, and the productivity gains must justify the cost when compared to simpler alternatives such as hardfacing with submerged arc welding or induction hardening.
The study also prompts reflection on the relationship between microstructure and macroscopic performance. The presence of retained austenite in the cladding layer, while potentially beneficial for toughness, may reduce hardness below optimal values. A careful balance must be struck through post-weld heat treatment to temper the martensite while retaining sufficient hard carbide dispersion.
Study Insights and Implications
The research confirms that plasma cladding is a highly effective method for enhancing the wear resistance of mining tools. The ability to precisely control dilution, composition, and microstructure through process parameter optimization represents a significant advantage over conventional hardfacing techniques. For engineering practice, the key takeaway is that successful plasma cladding of pick teeth requires a systematic approach encompassing base material preparation, process parameter optimization, and post-weld treatment—all working in concert to achieve the desired performance in service.