Composition and process analysis of optical fiber laser cladding

Laser cladding equipment composition

   Main structure of laser cladding processing head on inner hole surface is composed of laser optical circuit system, water cooling system, powder feeding system and gas circuit system.Due to the limitation of space, the design of laser cladding on inner hole surface has its particularity and difficulty compared with ordinary surface cladding.However, it is necessary to design and manufacture inner hole cladding, photoconductive tube, gas protection device, fixed adjusting device of powder inlet nozzle, and key short focal length integrating mirror.

(1) Inner hole cladding:
   Cladding head is designed for large diameter inner hole cladding and small diameter inner hole cladding respectively.The cladding head is suitable for wavelength ≤1064nm and has optical fiber interface QBH interface.The maximum depth of the inner hole can be melted to 1500mm, and the feed form is unidirectional axial feed.

(2) Integrating mirror:
Integrating mirror with focal length of 150mm.

(3) Optical waveguide:
   Design modularized the optical waveguide, which can appropriately increase or decrease the number of nodes of the intermediate pipe to meet the technical requirements of cladding of components with different inner hole lengths.

(4) Heat dissipating device:
   Due to the narrow space of inner hole cladding, heat is not easy to be emitted. Excessive heat accumulation will lead to changes in cladding structure, and even deformation.A cold air source is set on the outer surface of the pipeline to be machined. The cold air source is fed synchronously with the laser head, and the pipeline coated with the laser head is cooled.

Development of cladding process

  Inner hole cladding system and cladding parameters were adjusted and improved through a lot of cladding process tests.The cladding molding results show that the inner surface coating layer is uniform, smooth, without sand holes, cracks and defects, and the molding is good.In addition, the heat dissipation system reduces the influence of cladding heat on the treatment pipe, effectively reduces the deformation and machining removal of pipe fitting, which is conducive to reducing the inner cladding surface of pipe fitting, thus greatly reducing the subsequent processing process and reducing energy consumption.

Microstructure of cladding layer

   Microstructure of the cladding layer is fine dendrite without cracks, pores and other defects.The composite interface is clear and smooth with a bright white narrow band, indicating that the combination of cladding layer and matrix is metallurgical.Under high laser power, the effective energy density absorbed by matrix and cladding material is large, the pool residence time is short, the cladding layer structure is small and uniform, and the main structure is martensite and a small amount of residual austenite.

Hardness test of cladding layer

   Inner hole cladding is processed and the effective cladding thickness is maintained at 0.5mm.The hardness of the cladding layer and the matrix is stable, and the hardness of the cladding layer is slightly higher than that of the matrix.This is because Cr, Mo, Nb and other elements are strong carbide forming elements. When the heat input is large enough, more carbides will be produced.Combined with near the interface of micro hardness value is slightly lower than the hardness of cladding layer, this may be a component of cladding layer matrix and dilution effect and coated substrate near appear relatively bulky epitaxial growth of dendrites, effectively improve the wear resistance of the cylinder wall, at the same time, hardness value for subsequent cylinder wall cladding layer, grinding and other mechanical processing operations.

Wear resistance of cladding layer

   After washing and drying, the coated layer and the substrate are respectively taken as the original weight according to needs. The loss weight of the coated layer of the weight is significantly lower than that of the wearing weight of the substrate. For the samples, this technology is adopted to improve the cladding of the cylinder wall, and the wear resistance is better than that of the matrix, which is about 1.5 times of that of the substrate.

   Above is about the laser cladding process, if you want to know more information can visit our laser machine product column, thank you!!!!