The Industrial Application of Laser Cladding Technology

Centrifugal pumps are widely used in industries such as power, metallurgy, coal, and building materials to transport slurry containing solid particles, while valves control the flow of fluids such as air, water, steam, corrosive media, slurry, oil, liquid metal, and radioactive substances. The importance of pumps and valves cannot be overstated in modern industrial applications, as these products are constantly exposed to abrasive and corrosive media, requiring surfaces that are both hard, wear-resistant, and corrosion-resistant. Traditional surface hardening processes have limitations, which is where laser cladding technology steps in as a game changer for high-end pump and valve products.

Laser Cladding has gradually become the “secret weapon” in the development and production of high-end pump and valve products, such as centrifugal pump liners, balance sleeves, balance discs, ball valves, gate valves, and control valves. By harnessing the precision of laser technology, laser cladding is opening new doors for high-end pump and valve applications.

1. Advantages of Laser Cladding Over Traditional Methods

Traditionally, pump and valve sealing surfaces have been enhanced using the following methods:

Hard Chrome Plating: Coating thickness <0.1mm, primarily used for soft seals, prone to cracking and peeling;

Thermal Spray Welding: The mainstream method for hard seals, with coating thickness ranging from 1-1.5mm, prone to high thermal deformation and coating wear at thinner layers;

Arc Welding: Including MIG, TIG, PTA, with coating thickness ranging from 3-5mm, leading to high material wastage, high dilution rates, and uneven hardness distribution.

In contrast, laser cladding offers the following key advantages:

High Toughness: Fine-grained cladding structure ensures better wear resistance and some impact resistance at the same hardness level;

Strong Metallurgical Bond: With tensile strength >500 MPa, higher than the base material strength;

Low Dilution Rate: The dilution rate of laser cladding is ≤3%, making it 3-5 HRC harder than plasma cladding;

Fine Grained Structure: The cladding layer is dense, free from porosity, and exhibits isotropy;

Uniform Hardness: No soft spots, with a hardness variance of ≤3 HRC, ensuring excellent consistency within the effective depth.

2. Current Status and Advancements in Pump and Valve Laser Cladding Applications

In the 1990s, experts like Wang Aihua from Huazhong University of Science and Technology and Shi Shihong from Soochow University began researching laser cladding technology and materials for pumps and valves, achieving significant results. However, due to several constraints, the industrial application of laser cladding on pump valve hard sealing surfaces did not break through for many years.

Since 2010, the pump and valve industry has faced serious issues with low-level competition, over-supply of low-end products, and difficulty entering high-end markets. This has prompted many pump and valve companies to increase their investments in technological innovation and move towards producing high-end products for applications such as ultra-low temperature, nuclear power, and chemical industries.

In 2012, Wenzhou became home to a national-level laser and optoelectronics industrial cluster. Supported by local government initiatives, Wenzhou University, Zhejiang Gongshang University, and Zhejiang University of Technology began collaborating on several major laser projects for the pump and valve industry.

For instance, the team from Zhejiang University of Technology, led by Professor Yao Jianhua, developed laser cladding technology for Fe-C-Cr-Si-Mo alloys to manufacture valves. This process resulted in a metallurgically bonded cladding layer with an average hardness of 640 HV0.2, significantly outperforming the base material’s hardness of 170 HV0.2. This laser cladding method tripled the wear resistance compared to traditional processes.

3. Laser Cladding Process and Materials for Pump and Valve Products

In laser cladding, different base materials are used depending on the operating conditions. Common base materials include carbon steel castings, low-alloy steels, ferritic steels, austenitic stainless steels, martensitic stainless steels, nickel, and nickel alloys.

Pump and valve products are specialized items, and many applications involve safety concerns. The laser cladding process for pump valve sealing surfaces must adhere to strict standards to ensure the weld’s quality. Laser cladding should take into account factors like material, structure shape, and heat treatment properties. To standardize the process for pump and valve products, Jiuheng Optoelectronics has developed a set of “Laser Cladding Technical Requirements for Pump and Valve Sealing Surfaces” based on years of experience. These standards specify pre-weld temperature, heat treatment procedures, dilution rate controls, and dimensions for the cladding layer and transition layers.

4. Three Typical Applications of Laser Cladding in Pump and Valve Products

1. Laser Cladding on Polycrystalline Silicon Wear-Resistant Ball Valves

In the polycrystalline silicon industry, polycrystalline silicon wear-resistant ball valves with DN80 diameter are used in flue gas recovery devices to replace imported valves. The media consists of silicon powder and chlorosilane, with silicon powder hardness around HRC63-65, and the media temperature reaches 450°C. The valve is subject to strong erosion. The laser cladding of a metal-ceramic super-wear-resistant composite coating on the ball valve’s sealing surface replaces the original supersonic spray WC coating. This cladding structure exhibits excellent wear resistance and erosion resistance, significantly outlasting the imported valves.

2. Laser Cladding on High-Temperature Feedwater Pumps for Coal Chemical Industry

For high-temperature feedwater pumps in energy chemical companies, used to convey grey water with up to 0.5% solids content at 120°C, laser cladding on components such as impeller liners, pump body liners, balance sleeves, and balance discs enhances the hardness and wear resistance of the sealing surfaces. After 18 months of testing in high-particle-content coal chemical environments, the laser cladding-treated components showed up to 6 times better erosion resistance compared to traditional welding methods.

3. Laser Cladding on 2500BL High-Pressure Ball Valves

In industries like coal chemical, coal-to-oil, polycrystalline silicon, and petroleum, high-pressure special wear-resistant ball valves are widely used. Jiuheng Optoelectronics and Wallcolmonoy Corporation pioneered the use of laser cladding with Colmonoy 88 nickel-based alloys on 2500BL high-pressure ball valves. This technology improves valve performance, with a higher hardness and lower dilution rate compared to PTA processes, significantly enhancing the overall performance of the valves.

5. Conclusion

As modern science and technology advance, the working environments for components have become increasingly complex, requiring high surface performance. Pumps and valves, which are exposed to abrasive and corrosive media, must possess high hardness, wear resistance, and corrosion resistance. Laser cladding technology for high-pressure valve sealing surfaces enhances these properties. Compared to traditional methods, laser cladding significantly improves surface quality, wear resistance, and heat distortion, with precise layer control and excellent metallurgical bonding between the cladding and the base material. This process greatly extends the service life of pump and valve products, improving their technological content and added value. Laser cladding contributes to the domestic production of high-end valves, gradually replacing imported valves and enhancing industrial upgrading and regional innovation capabilities, significantly boosting China’s competitiveness in the global pump and valve market.