An Investigation On The Applying Fundamentals Of Powder Feeding Laser Cladding

In this paper. research reports relevant to the theory and application of surface laser cladding were retrieved in the recent years. According to the existing achievements on laser cladding, the state of art is reviewed and analyzed comprehensively. Some frontier problems related to fundamentals and applications of laser, cladding were put forward . Some developments in the application and experimental research have been made. The main content of the dissertation are as follow: ? Application research (1). The covering rate formulated by Pelliter was calculated in the first time. The relationship between the processing parameters and geometrical features of the powder feeding laser cladding were explained based on the covering rate. (2). To facilitate the present work .some basic concepts including the per unit time dilution. interaction time dilution, per unit length dilution and the different effective utilization of powder coefficient are formulated .On the basis of energy equilibrium, the equations of dilution and the effective utilization of powder coefficient expressing the relationship between the processing parameters and the processing results are proposed ,wffich coincide well with the experimental data. (3). The concepts of the specific energy input and the specific heat energy were formulated based on the experimental measuring method which have been proved be successful. The relationship between the processing parameters and the dilution and the effective utilization of powder coefficient were explained theoretically In the meantime, the theoretical method to analyze the variation of the microstructure and the properties of the cladded layer were formulated. (4) The physic model to express the movement of powder particles in the laser beam is formulated .On the basis of physic model, the equations expressing the interaction efficiency between the laser beam and powder particles and matrix are proposed. (5). On the basis of an analysis on the feeding pattern of the coating material, its behavior in the laser beam and the attenuation of laser beam by particle抯 cloud during the process of laser coating with automatic powder feeding , the methods to calculate the interaction efficiency of laser and particle抯 speed are presented . Analytical model of the cross-section of the cladded coating, the delth of the melt pool and the dilution were establised and expressions relating the parameters in the processes were obtained These analytical models were calculated by theoretical methods and determined by means of 3 metallography .The theoretical and experimental results coincide well with each other quantitatively and are consistent in reflecting the objective realty of the process.This model is helpful to find optimum process parameters. understand the major relationship between the process parameters and the results and desbtn on-time control system. (6). The concepts of heat and cold overlapping are formulated. In the meantime the theoretical and experimental methods to decide the overlapping rate are given. Under given assumptions . the methods to calculate the dilution. the effective utilization of powder coefficient and the effective utilization of laser during the broad-beam overlapping are formulated on the metallography measurement. The main mechanism of powder lose is caused by overheat.