Key processing technical parameters for high-speed laser cladding

High-speed laser cladding is an advanced rapid green metal surface treatment technology, has been the Ministry of Science and Technology as a replacement for chromium-plated technology. High-speed laser cladding has the characteristics of high processing efficiency, small follow-up processing volume, low cost and fine processing, and is a major technological breakthrough in the field of metal laser surface change technology.
In practice, the main technical parameters involved in high-speed cladding include two aspects: first, the debugging setting parameters of the equipment during the laser cladding process, called processing parameters, and second, the test evaluation parameters for the quality of the cladding effect after the completion of the cladding, called the detection parameters
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processing parameters mainly include laser power, matching rate, cladding speed, powder feed, powder delivery pressure and protection air pressure and other 5 key parameters.
(1) laser power: the energy output per unit of time of the laser. High-speed laser cladding is generally used with kW-class lasers, such as ZKZM-2000W and ZKZM-4000W produced in China and the United States, in the market to promote the application of more, to meet most of the scientific research and production needs.
(2) matching rate: the matching rate on the one hand affects the roughness of the surface of the cladding layer, on the other hand affects the efficiency of the cladding. High-speed cladding has a high tying rate, generally 60%-80% (the tying rate of ordinary cladding is 30%-50%).
(3) cladding speed: both the velocity of the cladding line and the efficiency of the cladding can indicate the size of the cladding speed. The ZKZM-4KW cladding line speed can be 5m/min-100m/min, with a cladding efficiency of 0.5-1.2 m2 per hour at a cladding thickness of 0.2-1.2mm.
(4) powder delivery: high-speed cladding powder delivery is mainly related to powder melting point characteristics, laser power, work piece movement line speed, both to ensure that the powder is fully melted, at the same time the powder can not be over-burned.
(5) powder pressure and protection air pressure, high-speed cladding powder delivery method for pneumatic powder delivery, powder pressure to match the amount of powder sent. The choice of protective air pressure should not only form a protective area around the melting pool, reduce oxidation, but also not be too large, affecting the flight path of the powder.
detection parameters are the measurement parameters for the quality of the cladding layer after the completion of the high-speed cladding, including 6 key parameters such as the thickness of the cladding layer, binding strength, porosity rate, dilution rate, surface roughness, hardness wear resistance, etc.
(1) cladding thickness: the thickness of the cladding layer mainly depends on the cladding power, the amount of powder sent and the speed of the work piece moving line. High-speed cladding can achieve 0.2-1.5mm cladding thickness, in special cases, multi-layer cladding can be carried out to achieve a thicker cladding thickness. However, the thickness of the cladding layer below 0.5mm can take advantage of high-speed cladding.
(2) Binding strength: The most important difference between high-speed laser cladding and thermal spraying is that high-speed cladding, while melting powder, also uses a small amount of energy on the molten chemical base, and the molten powder produces a metallurgical union by diffusing atoms at the interface of the molten substate. High-speed laser cladding and substate binding strength can be up to 360MPa or more.
(3) porosity: the main reasons for the appearance of voids are powder not melted enough, powder excessive oxidation, etc. , choose the appropriate cladding power, powder delivery and work part movement speed, high-speed cladding pore rate can be close to zero.
(4) dilution rate: refers to the extent to which the molten metal is diluted, expressed as a percentage of the substrate in the cladding layer. Dilution rate has a great influence on the performance of cladding. The size of dilution rate is mainly influenced by factors such as metal powder flow, cladding power and cladding rate. A large number of user data from China and the United States show that the dilution rate of high-speed cladding is extremely low and can be reduced to less than 3%.
(5) surface roughness: the surface flatness of the high-speed cladding layer is affected by many factors, such as tying rate, powder feed size, airflow pressure and machine tool motion accuracy. The parameters are matched properly, and the roughness of the high-speed cladding can achieve the effect of thermal spraying.
(6) hardness wear resistance: the hardness wear resistance of high-speed cladding depends mainly on the characteristics of the powder.
actual high-speed laser cladding work, according to the characteristics of powder, substrate and processing needs, set appropriate processing parameters to achieve the requirements of various technical detection indicators.