Welcome to the official website of Guangzhou Sanxin Metal Technology Co., Ltd.!
Introduction to Supersonic Flame Spraying Technology
Release time:
2020-12-09 17:31
Source:
Introduction to Supersonic Flame Spraying Technology
Supersonic Flame Spraying is a novel thermal spraying technique invented in 1981 by Browning of the United States. The core component of a supersonic flame spraying (HY0F) system is the spray gun, which consists of three main parts: a combustion chamber (where the spray material particles are thoroughly heated and accelerated), a Laval nozzle (which accelerates the flame jet to supersonic speeds), and a long, constant-cross-section nozzle (which further enhances the heating and acceleration of the spray particles). The working principle is as follows: Liquid fuel, such as kerosene, enters the combustion chamber through a small opening, where it is atomized and mixed with oxygen before being ignited. This triggers a vigorous gas-phase reaction, and the heat released during combustion causes the products to expand dramatically. As this expanding gas flow passes through the Laval nozzle, it is constricted and accelerated, forming a supersonic, high-temperature flame jet. This flame jet heats and accelerates the spray material particles to the substrate surface, thereby producing a high-quality coating.
Schematic diagram of supersonic flame spraying
Characteristics of Supersonic Flame Spraying
1. The flame jet has a high velocity but relatively low temperature, making it suitable for spraying carbide-containing materials.
2. The coating is dense and has low surface roughness.
3. The bonding strength is slightly lower than that of thermal spray, reaching over 70 MPa.
4. High spraying efficiency, but high fuel consumption and relatively high spraying costs.
5. High noise level (>120 dB); soundproofing and protective devices are required.
Common Materials Used in Supersonic Flame Spraying
Common Issues in Supersonic Spraying:
1. Trachoma
Porosity is a common issue in thermal spraying and also one of the most challenging problems to solve in high-end applications. Porosity can severely compromise the quality of both the coating itself and the finished products. Take roller applications as an example: porosity can affect the surface roughness of the product, creating tiny protrusions on its surface. In certain products used under corrosive conditions, porosity may lead to micropitting corrosion, thereby shortening the product's service life. Our company’s technical staff have years of accumulated expertise and employ stringent process controls to ensure that the sprayed coatings are completely free of porosity.
2. Dimples
Pitting is also a common issue in spraying, especially when applying chromium carbide coatings—pitting tends to occur very easily in such cases. The root cause of this problem lies primarily in the control of both the equipment and the powder used. Instability in the equipment and poor powder quality can both easily lead to pitting. Our company selects ultra-high-quality powders and employs the state-of-the-art P8000 supersonic spraying system, ensuring that after grinding and polishing, the coated products achieve a mirror-like finish.
3. Crack
Cracks are a very serious quality issue in spraying, primarily caused by poor process control, incorrect spraying parameters, and substandard spraying equipment. Cracks can severely compromise product quality and significantly reduce service life. Our company can guarantee that 100% of our sprayed coatings will be free of cracks.
4. Uneven coating
The unevenness of coatings is mainly caused by unstable spraying equipment. Some factories don't have robots and rely entirely on manual spraying, making it impossible to control coating thickness. Meanwhile, in some companies, defects in robot programs lead to inconsistent coating thicknesses. Additionally, certain customers are not fully aware of the importance of good uniformity. Products with poor uniformity incur higher grinding and polishing costs, and during the grinding and polishing process, they are prone to developing secondary non-uniformities. The reason is that in areas where the coating is thicker, the surface tends to slip once polished, while in thinner areas, the coating hasn't yet been fully polished. This unevenness in coating thickness ultimately affects the quality of grinding and polishing. Our company has introduced MOTOMAM robots—equipped with a 2.7-meter arm length—which are among the few large-scale robots currently available in the spraying industry. Relying on our engineers' skilled programming techniques, whether we're spraying ball valves or plate valves, or even mirror-finish rolling mill rolls, the uniformity never exceeds 0.03 millimeters. Excellent uniformity significantly reduces grinding and polishing costs.
5. Low coating hardness
This is an issue that many customers currently overlook. For example, when it comes to tungsten carbide coatings, some coating companies apply coatings with low hardness, while others achieve much higher hardness levels. Although it’s not necessarily true that the higher the hardness, the better, for tungsten carbide powders, if the normal hardness of a coating should be 1,200 HV, some coating companies may produce coatings whose hardness doesn’t even reach 100 HV. The main reasons behind this phenomenon are twofold: First, poor quality of coating equipment (a problem that exists in the vast majority of companies in this industry); second, the use of low-quality powder materials. Today, the processing standards in the coating industry vary widely, and many customers blindly opt for lower prices, neglecting the quality of the coating itself. As a result, even when applying identical tungsten carbide coatings, some coatings last extremely long, while others have a very short service life. The primary reason for this significant difference lies precisely in the low hardness of the coatings. Choosing a reliable supplier means selecting high-quality coating equipment and processes.
6. The coating has large pores.
The issue of large coating porosity is something many customers don't understand, because it's invisible to the naked eye and can only be observed under a metallographic microscope. All coatings produced by our company have undergone third-party testing, and their porosity rates are below 1%. The image below shows the metallographic microstructure of a WC-12Co coating.
In applications requiring high-pressure sealing and corrosion resistance, the porosity of a coating can significantly affect its quality. In the widespread use of high-pressure valves, one of the major causes of pressure leakage is the large porosity of the coating.
Supersonic spraying technology is being increasingly widely applied in China. However, achieving high-quality coatings is no easy task. The design of the coating must be closely integrated with the overall product design, and it’s crucial to select appropriate substrate materials as well as suitable machining processes before and after spraying. As surface treatment technicians, we not only need to understand the properties of various spraying materials but also master design solutions that seamlessly combine spraying technologies with product design—only then can we ensure that the coating’s full performance potential is realized.
Relevant Information
The complete set of plasma-sprayed equipment has been shipped to the customer’s site in Thailand.
Core spraying equipment: SX-80 plasma spray main unit, with a 15,000℃ flame suitable for multiple materials including zirconia and silicon carbide; powder feeding accuracy of ±1%, and coating thickness tolerance ≤ ±5 μm. Environmental protection support system: Customized soundproof booth + pulse dust collector—effectively addressing spray noise pollution while achieving highly efficient dust recovery, compliant with Thai environmental standards. Automated equipment: 6-axis industrial robot + intelligent spray cart, enabling precise spraying of complex workpieces and automated loading/unloading, boosting production efficiency by 40%.
On-site engineers provide hands-on training, focusing on the core operations of plasma spraying equipment such as the SX-80. Sanxin has customized a complete solution for its customers, including an automated spraying robotic arm, a soundproof booth, and a dust removal system—ensuring both high spraying efficiency and compliance with environmental standards.
Guangzhou Sanxin Thermal Spraying Turntable Shipment
Guangzhou Sanxin Company manufactures single-station and multi-station thermal spray turntables, which can be paired with plasma equipment, supersonic equipment, and arc equipment. We offer rapid, customized production tailored to customer requirements and product dimensions. A thermal spray turntable is a high-precision rotary worktable specifically designed for thermal spraying processes—including flame spraying, plasma spraying, and arc spraying. By providing controllable rotational speed and exceptional stability, it ensures uniform coating thickness on the workpiece surface, thereby enhancing spraying efficiency and quality.
SX-80 plasma equipment is being used at a customer site in Russia.
SX-80 plasma equipment is being used at a customer site in Russia.
Exclusive customized hotline, 24 hours a day, 7 days a week:
Email:CarrieFeng07@outlook.com
Address: Building 8, Liandong U Valley Guangzhou Nansha International Enterprise Port, Nansha Free Trade Zone, Guangzhou City, Guangdong Province
Copyright © 2023 Guangzhou Sanxin Metal Technology Co., Ltd. All Rights Reserved
Powered by www.300.cn
