Detection And Analysis Of Thermal Interaction With Diode Laser During Powder Pre-placed/Side-injection

Diode laser cladding technology has the advantages of low forming dilution rate and less crack defects,and has gradually become one of the effective means of strengthening and repairing components.In engineering application,with the increasingly complex surface morphology and state of metal parts,higher requirements are put forward for the precision and quality of laser cladding forming.At the same time,in order to reduce the difficulty of subsequent machining such as grinding and shorten the processing flow,it is also required to change the cladding process from "near shape" to precise forming control.However,due to the lack of in-depth study on the mechanism of thermal process,it is impossible to analyze the influence mechanism of heat source characteristics on the forming state.At present,the forming control of laser cladding can only rely on a large number of process tests and artificial experience to adjust and optimize the parameters.Therefore,in this paper,aiming at the thermophysical process of cladding forming,the thermophysical model of different characteristic stages is established by using high-speed camera and infrared system to collect and analyze the thermal process of powder,and the influence mechanism of different parameters on Thermophysical behavior is analyzed.The main research work is as follows:(1)In view of the influence of different characteristic stages on the forming state when the powder is pre-placed,combined with the functions of heat absorption,conduction,accumulation,dissipation and radiation,the heat balance state of different stages is studied,and the state equation which can describe the thermal process is established.Meanwhile,the action rule and influence mechanism of different parameters on the thermal physical behavior are qualitatively analyzed,and the laser work is verified by experiments.The effects of the parameters,such as the rate,the amount of defocusing and the particle size of the powder,on the different characteristic stages.(2)When the powder is fed by side-injection,the high-speed camera is firstly used to collect the powder beam behavior without laser.Combined with the designed image processing algorithm,the influence of different powder spot size and the position of the center of the powder beam on the free movement of the powder in space is analyzed,which provides an effective detection method for further analysis of the thermophysical effect of laser on the powder.By analyzing the thermophysical process of the laser interaction with the powder after the paraxial feeding of the powder,combining with the gray value of the image,the thermal process of the laser interaction with the powder under different process parameters is analyzed.At the same time,the temperature rise model of the powder particles under the effect of diode laser radiation is established,and the action behavior of different process parameters on the temperature change of the powder particles is studied.The validity and accuracy of the temperature rise model and its related functions are verified by infrared thermal imaging system.