Laser cladding is a thermal spray technology that focuses a laser beam on the surface of the target material to quickly melt and solidify it to form a coating. The determination of cladding quality usually requires consideration of the following aspects:
1. Coating appearance:
Observe the flatness, gloss and uniformity of the coating surface. A high-quality cladding coating should have a flat, smooth surface with no obvious pores, cracks or unevenness.
2. Bonding strength:
The bonding strength between the coating and the substrate is an important indicator for evaluating the quality of cladding. Tensile tests, shear tests, or impact tests can be performed to evaluate the bonding strength between the coating and the substrate.
3. Chemical composition:
Analyze the chemical composition of the coating to ensure it meets specified requirements. Detection of chemical components can be carried out using spectrometers or chemical analysis methods.
4. Microstructure:
Use a metallographic microscope or scanning electron microscope to observe the microstructure of the coating. The cladding coating should have a dense grain structure and no obvious crystalline defects or precipitates.
In addition, in practical applications, it is also necessary to consider the mechanical properties, corrosion resistance and wear resistance of the coating to comprehensively evaluate the cladding quality. Optimum cladding quality should meet specific engineering requirements and usage conditions.
During the laser cladding process, the observation of sparks is very important for evaluating the cladding quality and adjusting the cladding parameters. Observing sparks can provide information about the state of the molten pool during cladding and the heat input to the material. Here are the general methods and related indicators for observing sparks:
- Color of sparks: Observing the color of sparks can provide information about the temperature of the molten pool and the chemical reactions of the material. Different elements or compounds produce different colors of sparks during the cladding process. Typically, bright spark colors represent high temperatures and higher molten pool activity, while dull spark colors may mean cooler temperatures or less material reaction.
- The shape and frequency of sparks: Observing the shape and frequency of sparks can understand the stability of the molten pool and the efficiency of the cladding process. Stable spark shape and frequency indicate that the molten pool is in a good melting state, while unstable or jittering sparks may indicate that the molten pool is unstable or that the cladding parameters need to be adjusted.
- The direction of spark eruption: The direction of spark eruption also provides some key information. Under normal circumstances, sparks should erupt downward along the path of the laser beam and present a relatively uniform eruption, which indicates that the cladding process is proceeding within the expected range. If the spark deviates from the path of the laser beam, or if the eruption direction is uneven, it may indicate abnormal molten pool formation or uneven heating.
It should be noted that observing sparks needs to be carried out under suitable environmental conditions to avoid factors such as light interference from interfering with the observation of sparks. At the same time, sparks are only used as a reference indicator, and the final cladding quality needs to be determined through a comprehensive evaluation of other indicators. Therefore, in the laser cladding process, in addition to observing sparks, it is also necessary to combine other quality judgment methods to accurately evaluate
