Study on the Influence of High-Speed Laser Cladding Process Parameters on the Microstructure and Properties of Cladding Layers
Laser cladding technology prepares a metallurgically bonded coating on the substrate surface by adding materials and using laser as the heat source, realizing material surface modification and repair, and is widely used in industrial fields. This paper takes the ultra-high-speed laser cladding technology as the research object to explore the influence of its process parameters on the microstructure and mechanical properties of M2 high-speed steel coating on the surface of 9Cr2Mo steel substrate.
Limitations of Traditional Laser Cladding Technology
Although traditional laser cladding has advantages such as uniform coating structure and low heat input, it has obvious defects: the dilution rate often exceeds 10%, requiring a thicker coating to achieve the protective effect, and the surface roughness is high, requiring subsequent processing, resulting in material waste; the laser energy is concentrated in the substrate molten pool, which is prone to stress and cracks; the efficiency of large-area cladding is low, restricting the promotion of the technology.
Innovative Characteristics of Ultra-High-Speed Laser Cladding Technology
To solve the problems of traditional technology, the Hof Laser Technology Research Institute developed ultra-high-speed laser cladding equipment in 2017. This technology adopts the coaxial powder feeding method, controlling the convergence of powder in the laser beam above the molten pool, so that most of the laser energy directly acts on the powder, making the powder in a molten or semi-molten state before reaching the molten pool, thereby reducing the heat input to the substrate and greatly improving the cladding efficiency and powder utilization rate.
Influence Law of Process Parameters on the Microstructure of Cladding Layers
Studies have shown that process parameters have a significant impact on the grain size of the cladding layer: when the laser power is higher, the grain size increases significantly; the higher the cladding speed, the smaller the grain size; when the cladding pass spacing decreases, the grain size tends to increase. In general, with the increase of energy density, the grain size shows an increasing trend, among which the influence of laser power is more prominent.
Effect of Process Parameters on the Properties of Cladding Layers
Process parameters have a great influence on the microhardness of the cladding layer: when the laser power is higher, the hardness of the cladding layer increases, and the hardness distribution within the layer is uniform with small fluctuations; when the cladding speed decreases, the microhardness increases significantly; when the cladding layer spacing increases, the microhardness decreases; when the energy density increases, the microhardness increases significantly, but when the energy density is low, the forming of the cladding layer is poor, making it difficult to achieve good multi-pass overlapping.
Research Summary and Application Value
In summary, adjusting the process parameters of ultra-high-speed laser cladding and increasing the input energy density of the cladding layer can make the microhardness of the cladding layer more uniform and the average hardness significantly improved. This provides a technical basis for obtaining higher-quality cladding layers and is of great significance for expanding the application range of ultra-high-speed laser deposition technology and promoting its popularization and application.