Research On Extreme High Speed Laser Cladding Process And Performance Of Surface Coating Of Hydraulic Support Column

As the hydraulic support column is often used in the well which is filled with acidic and salt environment for a long time,there will be a series of failure problems caused by corrosion and abrasion.At present,electroplating is mainly used in advance to protect the columns in the industry,but the heavy pollution and high energy consumption induced by electroplating do not meet the requirements of green development in China.Therefore,based on 27 Si Mn steel substrate,this paper applied latest extreme-high-speed laser cladding technology to prepare a series of highperformance coatings that meet the requirements of actual working conditions,aiming at the repairing and protection of hydraulic support columns.A lot of work and experiments has been done and specific research contents and conclusions are as follows.(1)According to the characteristics and requirements of extreme-high-speed laser cladding technology,a specific experiment platform was built.This platform adopts fiber laser as the energy source,coaxial ring powder feeding method,horizontal machine tool as carrier,PLC and numerical control system.It has realized the predetermined goals of digital visualization of laser parameter control,stable powder feeding with a distance of 5 m,high-speed cladding and fast response.The technological requirements are guaranteed for cladding rotating workpieces with processing size less than 3000 mm and the processing diameter less than 630 mm.(2)According to the shape characteristics of the target workpiece and the technical characteristics of extreme-high-speed laser cladding,the program flow of workpiece cladding was formulated,and the processing process of extreme-high-speed laser cladding was described.At the same time,this paper also discussed the selection and optimization of process parameters.Through the process parameter exploration based on three-factor four-level orthogonal experiment on the steel pipe specimen,this paper researched the influence of three main process parameters(including laser power P,scanning speed v and powder feeding rate G)on the hardness,the surface quality,the geometric width and the geometric height of the coating.The optimal parameters obtained are as follows: the laser power,powder feeding rate,and scanning speed are2400 W,1.5 r/min,20 m/min or 40 m/min,respectively.(3)Relevant single-layer and multi-layer high-performance coatings were prepared according to the explored experiments,and the microstructure,hardness,wear resistance and corrosion resistance of the coatings were systematicly characterized and explored.The research revealed that the microstructure of the single-layer coating shows obvious rapid solidification characteristics.During the multi-layer cladding process,the grain size in the interior region became significantly larger,and the number of coarse columnar crystals increases in the interlayer area due to the influence of heat accumulation.At the same time,the influence of scanning speed on the microstructure and mechanical properties of the coating prepared by extreme-high-speed laser cladding was explored.The results showed that the maximum hardness of the coating is up to 540 HV,which is 2-3 times compared to that of substrate,therefore the wear resistance of the coating is also enhanced.In addition,the grains are refined and more uniform,contributing to the improvement of hardness and wear resistance of the coating when the scanning speed is increased.Finally,the 20-day salt spray test results showed that the high-performance coating prepared by extreme-high-speed laser cladding can fully meet the actual requirement of the enterprise.This paper focuses on the protective coating by extreme-high-speed laser cladding technology based on hydraulic support column surface.Aiming at the inherent defects of traditional repair methods,based on the common cladding technology,a new feasible scheme is provided for the repair of damaged columns or the protection of new columns.The research results are meaningful to protection and restoration of hydraulic support column based on the actual requirement of the enterprise.