Laser hardfacing involves using a laser to apply an overlay of hard and wear-resistant material onto functional surfaces. This process enhances the performance and durability of components, making them better equipped to withstand wear and tear. For further information on the process and applications of Laser Cladding, please click on the provided link.
There are various techniques for overlaying metals and hardfacing critical components. The most common techniques include Tungsten Inert Gas (TIG), Plasma Transferred Arc (PTA), High Velocity Oxygen Fuel (HVOF), and the Laser Cladding process. Every industrial process possesses its own distinct characteristics and advantages. In this blog post, we will delve into the advantages of utilizing laser cladding technology for hardfacing with Tungsten Carbides. Additionally, we will provide detailed answers to common queries related to this advanced process.
Benefits of Laser-Based Hardfacing
Lasers have higher power densities compared to other welding techniques. This means much less heat goes into the part to operate, resulting in a minimal Heat Affected Zone (HAZ). The Heat Affected Zone (HAZ) is known for its hardness, which is especially advantageous in critical components such as oil and gas drilling tools and mining equipment. A lower HAZ reduces the potential for base material cracking, significantly enhancing the overall durability of the component.
Hardfacing materials like Tungsten Carbide require a delicate balance of heat. Excessive heat can cause carbides to vaporize, creating porosity. However, hardfacing with lasers under the right conditions can result in minimal to no damage to the carbides. In applications requiring post-grinding of hardfaced surfaces, laser-clad hardfacing typically needs only about 0.020” (0.5 mm) of cleanup per side, significantly less than the 0.040” or more required for PTA and TIG processes. This reduced material removal translates to considerable savings in grinding costs.
FAQs
1. How is the hardfacing applied using lasers?
Tungsten carbide powder is fed into the laser nozzle at a precise rate, while a high-power laser melts both the base material and the tungsten carbide, creating a strong metallurgical bond.
2. What is the composition of Tungsten Carbide overlay?
In the oil and gas industry, the most commonly used tungsten carbide hardfacing material is often referred to as “60-40 WC.” This designation indicates that the hardfacing alloy comprises 60% tungsten carbides (either WC or W2C) by weight, combined with a matrix that has a hardness of 40 HRC. Matrix composition is typically a Nickel (Ni), Chromium (Cr), Boron (B), and Silicon (Si) matrix (NiCrBSi).
Picture 1: Spherical WC/W2C particles in NiCrBSi matrix
The Tungsten Carbide particles are spherical in nature and have a hardness of up to 2200 HV (Vickers Hardness) provide the bulk of wear performance. NiCrBSi matrix bonds with WC/W2C giving the required toughness.
3. Do Tungsten Carbide overlays have cracks?
Tungsten Carbide overlays with Laser cladding process typically exhibit cracks. However, these cracks do not lead to material delamination or chipping under the right process conditions.
4. Why is the buffer layer applied prior to Tungsten Carbide overlay?
The high hardness of tungsten carbide overlays can make them prone to chipping and delamination. To mitigate this risk, a buffer layer is used to create a transition zone between the base material and the hardfacing. This buffer layer helps absorb stress and prevents cracks in the overlay from propagating into the base material, thereby enhancing the overall durability and integrity of the hardfaced component.
Picture 2: 60-40WC cladding over Nickel based buffer layer
5. What is the wear performance of Laser Clad Tungsten Carbide overlays measured in?
Wear performance of Tungsten Carbide overlays are often measured in ASTM G65 abrasion resistance testing procedure. This test measures the wear resistance of the material by measuring the volumetric loss (mm3) after being tested against a rubber wheel and dry sand.
6. What is the maximum thickness of Tungsten Carbide overlays?
Tungsten carbide overlays are generally applied with a thickness between 0.040” and 0.080” (1 to 2 mm). This range allows for a robust, wear-resistant coating that enhances the durability of the underlying material. The specific thickness chosen can be tailored to meet the demands of different applications, balancing protection against abrasion and impact with overall performance requirements.
7. What is grind stock required on Tungsten Carbide overlays?
In applications that require post-grinding of hardfaced surfaces, laser clad hardfacing requires approximately 0.020” (0.5 mm) per side or less cleanup. This material cleanup is substantially lower when compared to 0.040” or higher cleanup required for PTA and TIG processes. This results in substantial savings in grinding costs.
8. What are the limitations of laser cladding with Tungsten Carbide?
Laser clad Tungsten Carbide overlays while being metallurgically bonded, still exhibit cracking. In applications where crack-free Tungsten Carbide coatings are required, HVOF process would be preferred.
Summary
Hardfacing with Tungsten Carbide is a critical process for extending the life and enhancing the performance of industrial components subjected to severe wear and abrasion. This technique involves applying a tungsten carbide overlay to a substrate, creating a durable, wear-resistant surface. Despite their high hardness, the overlays can be prone to chipping and delamination. To address these issues, a buffer layer is often used to transition which helps absorb stress and further cracks when properly executed. Tungsten carbide hardfacing is a valuable solution in industries such as oil and gas, mining, and construction, where components face extreme operating conditions.
Contact us today at info@synergyadditive.com for more information.