1 mm cladding layer achieves high-strength metallurgical bonding, significantly improving wear resistance.

Recently, our company has made significant progress in the application of laser cladding technology to the surface modification of wear-resistant parts. We have successfully clad a high-performance wear-resistant coating on a QT500-7 ductile iron substrate. The thickness of a single cladding layer is precisely controlled at 1.0 mm. The coating has a uniform and dense structure and achieves good metallurgical bonding with the substrate.

QT500-7 ductile iron, as an engineering material combining high strength and good plasticity, possesses excellent fatigue resistance and wear resistance. Its tensile strength is ≥500 MPa, yield strength ≥320 MPa, elongation ≥7%, and hardness ranges from 170 to 230 HB. Its strength is close to that of cast steel, while retaining the good vibration damping and machinability of cast iron. This material is widely used in the manufacture of wear-resistant components in machinery manufacturing, energy equipment, and rail transportation, such as gears for internal combustion engine oil pumps, drive shafts, turbine cylinder diaphragms, turbine valve bodies, wear-resistant bushings, and heavy-duty friction components like machine tool guideways. However, ductile iron faces surface wear and oxidation problems under long-term harsh working conditions, directly affecting the service life of components.

Laser cladding technology, as an advanced material surface modification and additive manufacturing technology, boasts significant advantages such as low dilution, strong adhesion, small heat-affected zone, and low surface roughness. The dilution rate, phase composition, thickness, grain size, and mechanical properties of the cladding layer can be precisely controlled, effectively meeting the specific environmental requirements of various industries. This technology can form a high-performance alloy coating on the substrate surface through a high-temperature, rapid melting process, effectively improving the wear resistance, corrosion resistance, and service life of components.

In this technological breakthrough, our company's technical team systematically optimized the cladding process parameters to address the industry challenge of high carbon content in ductile iron leading to the formation of hard and brittle phases and cracks at the interface. By rationally controlling key parameters such as laser power, scanning speed, and powder feeding rate, we successfully prepared a 1.0 mm thick cladding layer with uniform, dense, and defect-free microstructure. Experimental results show that the hardness of the cladding layer is significantly improved compared to the substrate, with an average hardness of 632.3 HV0.2, approximately 2.75 times that of the substrate (approximately 230 HV). For coatings clad with iron-based alloy powders, under the condition of a nominal vanadium carbide content of 30%, the average hardness reaches an even higher 920 HV0.2, with wear resistance 48.8 times that of the substrate and friction corrosion resistance 4.23 times that of the substrate.

The microstructure of ductile iron is typically a mixture of ferrite and pearlite, with fine and uniform spheroidal graphite distributed throughout the matrix. This ensures good vibration damping properties and provides a stable metallurgical foundation for subsequent cladding processes. During laser cladding, a high-energy laser beam rapidly melts and solidifies the alloy powder and the substrate surface, forming a metallurgical bonding layer. Studies have shown that optimizing cladding process parameters can effectively prevent crack and porosity formation. Cobalt-based alloy powder exhibits good crack resistance, and by appropriately matching laser power and scanning speed, a high-quality cladding layer can be obtained. Furthermore, research indicates that a preheating followed by postheating heat treatment process can effectively eliminate cracking problems in laser cladding, obtain a good cladding layer, restore the original dimensions of the workpiece, and improve overall surface performance.

The determination of the 1.0 mm cladding layer thickness is the result of achieving an optimal balance between process quality, metallurgical performance, and production efficiency. On the one hand, an excessively thin cladding layer (<1.0 mm) has too low a heat input, which may lead to poor bonding between the powder and the substrate, posing a risk of peeling. On the other hand, an excessively thick cladding layer (>1.5 mm) will drastically increase internal stress, potentially exceeding the material's strength limit and causing cracking. Therefore, a single-layer thickness of 1.0 mm has been verified as the most ideal process window under current conditions, effectively ensuring the metallurgical quality and service reliability of the cladding layer.

Based on this technology, our company can provide high-performance laser cladding services for wear-resistant parts in the fields of mining machinery, construction machinery, energy equipment, and rail transportation. Whether it's strengthening the surface of new parts for wear resistance or repairing and remanufacturing worn areas of old parts, this process can significantly extend the service life of components and reduce customer maintenance costs. Laser cladding technology repairs worn or corroded parts, effectively reducing equipment downtime and improving production efficiency. Especially for critical wear-resistant parts that operate under high wear and impact conditions for extended periods, laser cladding technology, by applying wear-resistant alloys to high-risk surfaces, enables the coating to adhere tightly to the substrate, forming a bonding strength 2-3 times stronger than traditional thermal spraying.

In the future, our company will continue to increase its R&D investment in laser cladding technology, continuously optimize process parameters and coating material systems, expand a wider range of application scenarios, provide customers with more efficient and reliable surface engineering solutions, and help the manufacturing industry achieve green and high-end transformation and upgrading.