Experimental Research On The Molten Pool Image Detection During Laser Cladding Process

Laser cladding technology has its own advantages in manufacturing performance. Whole amount of input heat is small, so is the deformation. Coating is bond with substrate in the form of metallurgy bond. The microstructure of the coating is fine and dense. Coating’s property is fine and barely affected by substrate due to its vary low dilution. These advantages has made its widely use in automobile, aerospace, defense and other industries. There are three main applications for laser cladding which are rapid prototype, renovation and surface properties’ changing.etc. Recent years, development of laser cladding equipment has made its use more widely. However, laser cladding still has its deficiencies, especially in its automation aspect.This topic take improving cladding process automation as starting point, take machine vision technology to measurement the molten pool which is formed by laser irradiation, seeking the regulations of molten pool and cladding bead when cladding parameters changed, lay a solid foundation for next establishing closed loop control system step which is in order to improve the cladding processing automation level. Therefore, this research mainly focuses on the following aspects:Firstly background and significance of the topic were introduced. Ten current situation of research and development of molten pool detection in laser cladding was reviewed. Limitations and deficiency were analyzed. Regulations that parameters of molten pool and cladding bead and layer changes as the cladding parameters changed and the two regulations’ relationship were determined as the main content in this article. Molten pool parameters include its area, length and width. Cladding bead parameters include its height, width, depth of HAZ and dilution.Molten pool hardware system was established according to the characters of molten pool. The hardware system mainly includes camera and lens with appropriate parameters and filters and attenuation filters. According to the characters of molten pool image acquired by the camera, right algorithms were taken into use to process the molten pool image. The image processing program was written in Labview circumstance.Taking advantage of pre-placed laser cladding feature that different kind of metal powder can be easily pre-placed on the same substrate, when cladding processing parameters change, change regulations of molten pool and cladding bead with three different kind of metal powder. The three different kind of powder was Fe327, SF6, and Ni55 which were taken from three common self-fluxing alloyed powder types namely Fe-based, Co- based and Ni- based alloy. And the outcome indicated that different kinds of powder had different regulations.Taking practical application into account, powder injection cladding is mostly widely used. So it’s necessary to do research on powder injection cladding. As for this part, two steps were taken to do the research and both step used Ni55 self-fluxing alloy powder. First step, powder injection single bead laser cladding technology was used to analyze how molten pool properties(area, length, width) and cladding bead quality(cross section area, height, width, HAZ) change when cladding processing parameters(powers, scan speed, powder feeder rate) changed. Based on the single bead research, molten pool and cladding quality when taking multi-bead laser cladding process were also analyzed.