At present, the main technologies used in the repair of engineering equipment include arc spraying, heat treatment, surfacing welding, etc., but with the continuous development of laser cladding technology, the performance of coating preparation is becoming more and more excellent, and the efficiency is also increasing, providing new methods and new ideas for the repair and remanufacturing of engineering equipment.
Application prospect
Compared with high-end manufacturing fields such as aerospace, automobile remanufacturing and ship remanufacturing, the use of laser cladding for engineering equipment maintenance and remanufacturing has a slower development and a lower level. In order to ensure the integrity rate and reliability of engineering equipment, the advanced results of laser cladding in other fields are used for reference, and the two aspects of surface strengthening and improving corrosion resistance are studied.
Surface strengthening
Engineering equipment structure is complex, a wide variety of parts, some parts are not only required to have enough stiffness and toughness, but also require the surface to have enough hardness and wear resistance, such as gear tooth surface, transmission shaft mating surface, etc., to seek better wear resistance and higher surface hardness.
In terms of improving the wear resistance of the parts, the Fe-based cladding layer is prepared by laser cladding technology on the surface of 45 steel. After optimizing the process parameters, the dense and defection-free cladding layer is obtained, and its hardness is significantly higher than that of the matrix. The problems of excessive wear and cracks in the curved shaft journal are effectively solved. During the task, the camshaft of the tank engine will bear the impact of the valve opening and closing periodically, which will cause the peach-tip wear failure of the CAM. Fe90 Fe-base alloy powder was laser coated on the surface of tank camshaft to obtain the coating without cracks, pores and dense structure, and its wear resistance was greatly improved.
In order to improve the hardness of parts, Fe60 alloy and Ni60 alloy laser cladding coatings were prepared on 45 steel surface, and their properties were compared. Although the Ni60 alloy cladding layer has higher hardness, it has more cracks, while the Fe60 alloy cladding coating not only has higher hardness in the bonding zone, but also has good metallurgical bonding without obvious defects. It is concluded that Fe60 alloy powder is more suitable for laser cladding treatment on 45 steel surface.
Improve corrosion resistance
The vast majority of the parts of the engineering equipment are metal materials, although the parts have a certain anti-rust protection when they just appear, such as electroplating, coating and other surface engineering technology, but the equipment is generally outdoors and the conditions are more harsh open-air environment, the exposed metal is still easy to produce oxidative rust. Therefore, the corrosion resistant coating can be prepared by laser cladding technology to block the direct contact between the metal and the atmosphere and moisture, so as to play the role of anti-rust protection.
It is found that the corrosion resistance of cladding layer can be significantly improved by adding and controlling external field conditions. The surface morphology, cross section size, solidification structure, number of cracks and microhardness of the laser cladding coating were investigated in detail by using pure iron as matrix and Ni60 self-fusible alloy powder as cladding material with the aid of single alternating current, single steady-state magnetic field and electro-magnetic composite field. It has been proved that a high quality laser cladding coating can be obtained by using a small electro-magnetic composite parameter, which improves the corrosion resistance of the coating. This scheme provides technical guidance for strengthening engineering equipment by laser cladding technology. In summary, laser cladding technology provides a certain feasibility for improving the corrosion resistance of engineering equipment.
Since 1974, Gnanamuthu laser cladding a layer of metal on the surface of a metal substrate and obtained the relevant patent, the technology has been studied for nearly half a century, and at present, a lot of experience and experimental data have been accumulated. However, its research and application in the repair and strengthening of engineering equipment are still few, in order to achieve the promotion of laser cladding in the field of engineering equipment maintenance and remanufacturing, the future can be studied from the following directions:
1. Absorb the accumulated results of laser cladding technology in high-end industry research, and use it in engineering equipment, so as to improve the status quo of low maintenance and remanufacturing of engineering equipment and slow development.
2. The application of laser cladding technology in military and civil bridge erecting machines is still less. After analyzing the cracking of the steel plate in the large arm of the bridge erecting machine, WISCO Research Institute found that the equipment has far not reached its service life, and the failure of the steel plate belongs to the fatigue fracture of the slag inclusion part of the weld, and it expands along the path of the weld. At the same time, there are brittle martensitic structures in the weld. The laser cladding technology is used to treat the steel plate of the big arm of the bridge erecting machine, which can not only effectively improve its mechanical properties, but also enhance its corrosion resistance and oxidation resistance, providing new ideas and new methods for the maintenance and remanufacturing technology of military and civil bridge erecting equipment.
3. The stability of metallurgical bonding strength between cladding layer and substrate needs to be improved. Due to the very fast heating and cooling speed of the cladding layer, the thermal expansion coefficient, melting point and wettability of the cladding material and the base material are different, which makes the metallurgical joint prone to crack, so the effect of metallurgical combination needs to be improved.
4. The process parameters of laser cladding were optimized and upgraded. In laser cladding, how to quickly and efficiently find the optimal solution of a set of process parameters has always been a key topic for researchers, and the appropriate process parameters are of great significance for the preparation of high-quality coatings.
Xi'an Guosheng Laser Technology Co., Ltd. is a high-tech enterprise specializing in R&D, manufacturing and sales of automatic laser cladding machine, high-speed laser cladding machine, laser quenching machine, laser welding machine and laser 3D printing equipment. Our products are cost-effective and sold domestically and abroad. If you're interested in our products, please contact us at bob@gshenglaser.com.