CLADDING TECHNOLOGY SHANXI CO., LTDPreparation of Cemented Carbide-Steel Bimetallic Composite Material by Submerged Arc Automatic Cladding
Overview of the Study
The research conducted by Cai Mei, Wang Shuangcheng, Niu Libin, and Xu Yunhua, published in the Journal of Heat Processing in 2008, focuses on the preparation of cemented carbide/steel bimetallic composite materials using submerged arc automatic welding (SAW) cladding. Cemented carbide, typically composed of tungsten carbide (WC) particles in a cobalt (Co) or nickel (Ni) binder, is renowned for its exceptional hardness and wear resistance. However, cemented carbide is brittle and difficult to machine, limiting its application in large components. By cladding cemented carbide onto a steel substrate, the composite material combines the wear resistance of cemented carbide with the toughness and machinability of steel, creating a versatile material for demanding industrial applications.
Process Parameters and Welding Configuration
The authors investigated the effect of welding parameters on the microstructure and properties of the cemented carbide/steel composite. The following table summarizes the typical process parameters used in the study:
| Parameter | Value | Notes |
|---|---|---|
| Welding method | Submerged arc welding (SAW) | Single-wire, single-flux |
| Wire diameter | 2.0–3.0 mm | Flux-cored or solid wire with carbide particles |
| Welding current | 250–350 A | Higher current increases penetration and dilution |
| Travel speed | 20–40 cm/min | Lower speed increases heat input and layer thickness |
| Shielding flux | Rutile-type or basic-type | Provides slag protection and influences microstructure |
| Layer thickness | 2–6 mm | Multi-pass welding for thicker layers |
| Preheat temperature | 100–200 °C | Reduces residual stress and cracking risk |
The welding configuration involved depositing layers of cemented carbide powder or flux-cored wire containing carbide particles onto a steel substrate. The flux provided shielding and slag coverage, protecting the molten weld pool from atmospheric contamination and influencing the solidification microstructure.
Microstructure and Mechanical Properties
The microstructure of the cemented carbide/steel composite was characterized by the distribution and morphology of WC particles within the matrix. The authors observed that the WC particles were distributed relatively uniformly throughout the overlay layer, with some particles located at the fusion zone interface. The matrix microstructure consisted of martensite, retained austenite, and carbides, depending on the cooling rate and composition.
The following table summarizes the mechanical properties of the composite material:
| Property | Value | Comparison with Substrate |
|---|---|---|
| Hardness (HV) | 800–1200 | 3–5 times higher than steel substrate |
| Tensile strength | 800–1000 MPa | Comparable to high-strength steel |
| Impact toughness (J) | 15–30 | Lower than substrate but acceptable for wear applications |
| Wear resistance | 5–10 times higher | Significantly improved abrasion resistance |
| Bond strength (MPa) | 350–500 | Meets ASTM A263 requirements |
The authors noted that the hardness of the composite material was primarily determined by the volume fraction and distribution of WC particles. Higher WC content led to increased hardness but reduced toughness. The optimal balance between hardness and toughness was achieved with a WC content of 40–60 vol%.
Engineering Applications and Quality Control
The cemented carbide/steel composite material is suitable for a wide range of applications, including mining equipment, agricultural machinery, and industrial components subjected to severe abrasive wear. The following considerations should be taken into account during fabrication and quality control:
- Surface preparation: The steel substrate must be thoroughly cleaned and prepared to ensure good bonding between the composite layer and the base metal.
- Welding sequence: Multi-pass welding should be performed with careful control of interpass temperature to prevent cracking and microstructural degradation.
- Non-destructive testing: Magnetic particle inspection (MT) and ultrasonic testing (UT) should be used to detect surface and subsurface defects in the composite layer.
- Mechanical testing: Hardness testing, bond strength testing, and impact testing should be performed on representative samples to verify that the composite material meets the required specifications.
The authors also discussed the importance of post-weld heat treatment (PWHT) in improving the toughness of the composite material. A PWHT cycle at 550–600 °C for 2–4 hours can reduce residual stresses and improve the ductility of the matrix without significantly reducing the hardness of the WC particles.
Study Insights and Concluding Remarks
The research by Cai Mei and colleagues demonstrates the feasibility of producing high-performance cemented carbide/steel bimetallic composite materials using submerged arc automatic welding. The study provides valuable insights into the relationship between welding parameters, microstructure, and mechanical properties, offering practical guidance for engineers involved in the fabrication of wear-resistant components. The ability to combine the exceptional hardness of cemented carbide with the toughness and machinability of steel opens up new possibilities for extending the service life of industrial equipment. For engineers working in the mining, agricultural, and manufacturing industries, this study offers a reliable methodology for producing cost-effective and high-performance composite materials that meet the demanding requirements of abrasive wear applications.