The change of different scanning speeds has a significant impact on the quality of the cladding layer. The suitable scanning speed makes the cladding layer continuous, smooth, smooth and free of pores. Too fast scanning speed will cause the cladding layer to be discontinuous and appear intermittent beads. shape, with voids.Other factors affecting the quality of the exhaust valve laser cladding layer are the pressure of the protective gas. The test found that if the protective gas pressure is too large, the surface roughness will increase, the surface will be uneven and smooth, and wrinkles will occur. If the pressure of the protective gas is too small, first, the surface of the cladding layer cannot achieve the purpose of anti-oxidation, which will cause the oxygen in the air to participate in the action of the laser and the powder, resulting in defects in the cladding layer.
Lens contamination can also play a role. Because the beam and the shielding gas are coaxial, it not only protects the molten pool, but also protects the lens. In the process of laser processing, splash phenomenon is inevitable, and the protective gas can prevent the slag from flying to the focusing lens, so the pressure of the protective gas cannot be ignored.
Tooling fixtures are also an important factor affecting the quality of the cladding layer. During the laser cladding process, the tooling fixture must ensure that the exhaust valve can rotate at a constant speed, so that the scanning speed remains unchanged. The beam irradiation position coincides with the slotting position, otherwise, the cladding layer will deviate, causing the workpiece to be scrapped.
- In the exhaust valve pre-coating process, when the laser power, spot diameter and scanning speed are constant, the coating thickness is 1mm to 2mm, and the blending ratio of alloy powder and adhesive is 2%, an ideal the surface quality of the laser cladding layer.
- The best process parameters for laser cladding of automobile exhaust valves are: laser power 1.8kW ~ 2.1kW, spot diameter 4.5mm ~ 5mm, scanning speed 5mm/s ~ 6mm/s. The cladding layer is continuous, flat and smooth , basically no pores, stable process, can be used for industrial production
Laser cladding is also called laser cladding or laser deposition. It uses high-energy laser as the heat source and metal alloy powder as the welding material. The laser and alloy powder (or wire) act simultaneously on the metal surface to quickly melt to form a molten pool, and then quickly Solidification forms a dense, uniform, and controllable thickness metallurgical bonding layer.
The Characteristics Of Laser Cladding Technology
Compared with many traditional surface treatment technologies, laser cladding technology has the following significant advantages and characteristics:
- High metallurgical bonding strength. Laser cladding uses the extremely concentrated energy of a high-energy laser beam to micro-melt the workpiece surface instantly, and at the same time completely melts the alloy powder preset on the workpiece surface or automatically transported synchronously with the laser beam. After the laser beam is scanned, the substrate rapidly solidifies through self-cooling, resulting in a dense coating alloy layer that is metallurgically bonded to the substrate.
- Optional hardness and thickness. After laser cladding, the hardness of the cladding layer can be selected between HRC20-62, and the cladding thickness can be adjusted as needed.
- Wear resistance and corrosion resistance. Laser cladding can form an alloy layer with corrosion resistance, wear resistance and excellent properties on the surface of ordinary carbon steel workpieces, thereby extending the service life of the workpiece.
- Reduce costs and energy consumption. Laser cladding can produce high-performance alloy functional layers on low-cost substrates by forming alloy coatings with different metallurgical combinations, alloy compositions and properties on the surface of the substrate, thereby saving material costs.
- The cladding is of high quality. It has small deformation, good mechanical repeatability, dense interface structure, fine grains, and no defects such as holes and cracks.
The Main Features Of Laser Cladding Machine
- The cooling rate is fast (up to 106K/s), which is a rapid solidification process. It is easy to obtain fine-grained structures or produce new phases that cannot be obtained in equilibrium, such as unstable phases, amorphous states, etc.
- The coating dilution rate is low (generally less than 5%), and it has a strong metallurgical bond or interface diffusion bond with the substrate. The laser cladding machine can obtain a good coating with a low dilution rate by adjusting the laser process parameters, and the coating Layer composition and dilution are controllable;
- The heat input and distortion of the laser cladding machine is small, especially when high power density and rapid cladding are used, the deformation can be reduced to the assembly tolerance of the part.
- There are almost no restrictions on powder selection, especially for depositing high-melting-point alloys on the surface of low-melting-point metals;
- The thickness range of the cladding layer of the laser cladding machine is wide, and the thickness of the single-pass powder feeding is 0.2-2.0mm.
- It can carry out selective welding, consumes less material, and has excellent performance-price ratio;
- Beam aiming can make inaccessible areas welded;
- The laser cladding machine process is easy to automate.
Common Application Industries Of Laser Cladding Technology
Laser cladding technology is a multi-disciplinary edge discipline involving laser technology, material processing technology, sensing technology and computer technology. It is also an emerging advanced cnc and micro manufacturing technology. Basically, a process in which high-energy-density laser radiation is used to melt it on the surface of a substrate and quickly solidify to form a surface coating that is metallurgically bonded to the surface of the substrate.
After decades of development, laser cladding technology has entered actual industrial applications from the laboratory, and has been widely used in metallurgical industry, coal industry, petrochemical industry, transportation, machinery manufacturing, mold making industry, hardware tools and other industries. Wide range of applications.
1.Metallurgical Industry
According to preliminary estimates, the national steel industry consumes 10 billion yuan every year on only important parts and components on various steel rolling production lines. The traditional method is mainly to replace the parts of these equipment, or even scrap them because the parts cannot be used or replace the whole machine. The damaged, failed and scrapped parts or the whole machine are basically treated as scrap, resulting in a lot of waste of resources. Laser cladding repair equipment can prepare high-performance alloy surfaces on the metal substrates of parts, which can significantly improve its surface wear resistance, corrosion resistance, heat resistance, oxidation resistance and electrical properties. It can not only extend the service life of new parts It can also repair worn parts by cladding and restore their original dimensions, thus reducing the replacement cycle of parts.
2.Mining Machinery Industry
Characteristics of mining machinery and equipment: they are bulky, expensive, difficult to load and unload, and require a large amount of maintenance and repair work. Therefore, when parts stop operating due to wear and damage, huge economic losses will be caused. Laser cladding can remanufacture the surface of new and old parts, such as hydraulic cylinders, columns, etc., thereby effectively improving the wear and corrosion resistance of the parts and extending the service life of the parts.
Generally used are:
- Coal shearer: main frame, rocker arm, gears, gear shafts, various bushings, articulated frames, oil cylinders, oil cylinder seats, guide shoes, sprockets, rail pin wheels, driving wheels, picks, etc.
- Tunnel boring machine: cylinder, bracket, shaft, various bushings, picks, etc.
- Scraper conveyor: middle chute, transition chute, gear box, gears, gear shafts, spiral bevel gears, shaft parts, etc.
- Hydraulic support: hinge holes of oil cylinders, bases and supports, various bushings, etc.
3.Petrochemical Industry
In the petrochemical industry, since equipment works in harsh environments for a long time, products are prone to corrosion and wear. Regular maintenance of equipment parts is particularly important. Laser cladding can repair failed parts by cladding, restore the original dimensions, and effectively restore the use of the equipment.
The modern petrochemical industry basically adopts a continuous mass production model. During the production process, machines work in harsh environments for a long time, resulting in damage, corrosion, and wear of components within the equipment. Parts that often cause problems include valves. , pumps, impellers, journals, wheels, discs, bushings, bearing bushes, etc. of large rotors. Moreover, these components are very expensive. There are many types of parts involved, and most of them are complex in shape, making them difficult to repair. But because of the emergence of laser cladding technology, these problems are no longer a problem.
4.Transportation Industry
The transportation industry includes land, waterway, air transportation, etc. Transportation equipment is characterized by high frequency of use and complex and changeable environments, resulting in the need for regular maintenance of the equipment. Laser cladding can repair various parts and restore them to their original dimensions, thereby effectively extending the service life of the parts.
- The marine environment is harsh, with high humidity and salt content, and marine ship equipment is prone to wear and corrosion. Marine engineering equipment and ship components are technologically complex and valuable, resulting in huge waste when they fail and are scrapped. Domestic shipyards have applied laser cladding technology to carry out high-precision repairs on ship impeller corrosion, engine cylinder liners and diesel engine intake and exhaust valve disc cone surface wear, and achieved good cladding effects, restored functions and improved wear resistance, Corrosion resistance.
- In automotive industry applications, laser technology was first used for cutting and heat treatment. With the development of cladding technology, it gradually developed into flexible additive manufacturing technology. For example, the sealing tapered surface of the engine’s exhaust valve is clad with Stellite alloy and is the first automotive part to adopt this technology. The annular surface of the exhaust valve seat of Italian Fiat automobile engines and the exhaust valve seat of American automobiles are all made of laser cladding heat-resistant alloy. Currently, the Beijing Machinery Science and Technology Guochuang Lightweight Research Institute is cooperating with Guangxi Yuchai to clad the wear-resistant and high-temperature resistant alloy on the annular surface of the engine valve seat, and has also achieved phased results.
- In the aerospace field, another application of laser high-speed cladding technology in the aerospace field is the “mobile parts repair hospital”. The core is to use laser high-speed cladding technology to repair or manufacture key parts on the battlefield. It can even use satellite communications equipment to transmit data about manufactured parts. In the absence of data information, reverse engineering can also be used to obtain the external contour information of the parts to be built, and repair or manufacturing work can be completed after necessary processing. The most distinctive advantage of laser high-speed cladding technology is that through improved powder feeding technology, real-time continuous changes in material composition in parts can be achieved, and high-performance parts with gradient composition materials can be manufactured.
For wear-resistant spare parts of titanium alloy machining equipment used in aviation, the wear of the spare parts after laser cladding is only 4.2% of the original parts, and no wear occurs until the counter-grinding wire rope is worn out.
5.Manufacturing And Remanufacturing Of Electrical Equipment And Parts
Electrical equipment is distributed in large quantities and operates continuously, and its parts have a high probability of damage. Steam turbines are the core equipment of thermal power generation. Due to the special working conditions of high temperature and heat, damaged unit parts such as main shaft diameter, moving blades, etc. need to be repaired regularly every year. Gas turbines often suffer damage due to their operation at high temperatures of up to 1300°C. Laser remanufacturing technology is used to repair all defects and restore its performance at a cost that is only 1/10 of the price of a new unit.
The Advantages Of Laser Cladding
Laser cladding solves the problems that traditional repair methods cannot solve: material selection limitations, process thermal stress, thermal deformation, coarse material grains, and difficulty in ensuring the bonding strength with the matrix. It can even prepare a metal surface that is better than the base material. While restoring the use of the parts, it can also effectively extend the service life of the parts, greatly reducing the production cost of the company.
Be-Cu China Laser cutting shop‘s high-speed laser cladding is not only faster than traditional laser cladding, the surface is smoother and smoother, and the processed parts can be put into production with just finishing processing, saving a lot of machining time and Cost will be a major technical force in laser surface remanufacturing in the future.
The Application Of Laser Cladding Process In Valve Field
Laser cladding technology is a modern surface repair technology that can be applied to various industries, including the valve industry. Valve is an indispensable part of the industrial fluid control system. The sealing performance, wear resistance, corrosion resistance and service life of the valve are directly related to the stability and safety of the system. Laser cladding technology can be used to repair, strengthen, and improve problems such as wear, corrosion, and cracks in valve materials. The following are some products that laser cladding can be used in the valve field:
1.Valve Sealing Surface
The valve sealing surface is one of the important parts of the valve. During use, the valve seat is often affected by factors such as high temperature, high pressure, and corrosion, resulting in a decrease in its sealing performance. The sealing performance is important to the service life and safety of the valve. Influence. Laser cladding technology can be used to repair and strengthen the valve sealing surface to improve the valve’s sealing performance. Using laser cladding technology for repair and reinforcement can make the sealing surface of the valve have higher wear resistance, corrosion resistance and high temperature resistance.
2.Valve Seat
Valve seats are usually made of wear-resistant alloys to enhance the wear resistance of the valve. During use, the valve seat will suffer from wear and corrosion, resulting in a decrease in valve sealing performance. Laser cladding technology can be used to reinforce and repair valve seats, improving the service life and sealing performance of the valve.
3.Valve Valve Body
Valve The valve body is one of the main components of the valve and is responsible for controlling the flow of fluid. Valve The valve body is usually made of steel or cast iron and has certain wear resistance and corrosion resistance. During use, the valve body will also experience wear and corrosion, resulting in a reduction in the service life of the valve. Laser cladding technology can be used to reinforce and repair valve bodies, improving the service life and wear resistance of valves.
4.Valve Stem
The valve stem is one of the key components of the valve. It is responsible for controlling the opening and closing of the valve and regulating the flow. Valve stems are usually made of stainless steel or other alloy materials, which have high wear resistance and strength. During use, the valve stem will also suffer from wear, corrosion, fatigue cracks and other problems, causing the valve to operate inflexibly or completely fail. Laser cladding technology can be used to strengthen and repair the surface of valve stems, improving the service life and operational reliability of the valve.
5.Valve Bonnet
Valve bonnets are usually made of steel or cast iron and are responsible for protecting the valve’s internal components from external contamination. During use, the valve cover will also be affected by corrosion and wear, resulting in a decrease in its sealing performance. Laser cladding technology can be used to repair and reinforce valve bonnets, improving the service life and anti-fouling capabilities of valves.
6.Valve Ball
The valve ball is the main component of the ball valve, which directly affects the service life and operational reliability of the valve. During use, the valve ball is often affected by factors such as high temperature, high pressure, and wear, resulting in cracks, fatigue, deformation and other problems on its surface. Laser cladding technology can be used to strengthen and repair the surface of the valve ball, improving the service life and operational reliability of the valve.
7.Valve Valve Plate
The valve plate is a key component for valve operation and has an important impact on the operating efficiency and safety of the valve. During use, the valve plate will also be affected by factors such as high temperature, high pressure, and wear, leading to problems such as cracks, fatigue, and deformation on its surface. Laser cladding technology can be used to strengthen and repair the surface of valve plates, improving the service life and operational reliability of the valve.
The application of laser cladding technology in the valve field has the following advantages:
High precision: Laser cladding technology uses high-energy-density laser beams for processing, which can achieve high-precision processing on a microscopic scale, with an accuracy of up to several microns, which can meet the high requirements of valve parts processing.
High efficiency: Laser cladding technology adopts a non-contact processing method, which will not cause deformation and damage to parts, and can achieve fast and efficient processing, saving production time and costs.
Excellent material properties: Laser cladding technology can control the structure and performance of the material during the processing process, and can improve the hardness, wear resistance, corrosion resistance and other performance indicators of the material, giving valve parts a better service life and durability. .
Environmental protection and energy saving: Laser cladding technology adopts a non-contact processing method, which does not require the use of large amounts of chemicals required in traditional processing methods such as cutting fluids and coolants. It can reduce environmental pollution and energy consumption, and meets the requirements of environmental protection and energy saving.
In short, laser cladding technology has broad application prospects in the field of valves and can solve problems such as wear, corrosion, fatigue cracks and other problems that occur in valve materials during use. In the valve industry, laser cladding technology has become an important technical means for valve repair and reinforcement, providing guarantee for the reliable operation of valves.