Study Of Laser Machining Ceramic Green Bodies

Because of good properties on high strength, high hardness, good high temperature performances, abrasion resistant and low density, ceramics have been used widely in all kinds of industrial fields. However, ceramics are extremely hard to molding and machining because of high hardness, brittleness and poor reliability, which hinders their application and development.In this paper, the laser machining performance of the gelcasting green body of Al₂O₃, ZrO₂, Si₃N₄ and SiC was studied with 3D laser machining. The influence of parameters on the machining quality and efficiency was systematically analyzed, including the laser power, scanning speed, scanning pitch and the solids loading of green body, in order to get optimum parameters.Research found that the machining quality has something to do with the laser power, scanning speed, scanning pitch and the solids loading of green body. For example, both the machining depth and the surface roughness decreased in total with increasing scanning speed. Moreover, with the increase of scanning pitch, the machining depth decreased in total while the surface roughness increased at the same time. The machining depth of Al₂O₃ and ZrO₂ was deeper than Si₃N₄ and SiC, and it reached a maximum for ZrO₂. In addition, nitrogen purging was applied for Si₃N₄ and SiC, which could obtain a good machining surface and also ensured the machining continuity. When the laser energy density was a bit higher, the crystal grain of pure Al₂O₃ powder and green body grew up to an orderly pattern after laser machining, and glomeration effect and serious surface sintering were discovered. For the powder and green body of ZrO₂, phase transformation of zirconia from tetragonal to monoclinic occurred in accord with the grain growth. Nevertheless, there was no obvious change for the particle size of Si₃N₄ and SiC in spite that the surface was gasified.Laser machining parameters matched with these four material systems were chosen, which brought the manufacture of the 3D complex-shape parts of ceramics into reality. It is a highly efficient and short-process way for the laser green machining of ceramics to manufacture complex-shape parts. Therefore, it has great theoretical significance and practical value for the structural ceramics with multi-purposes and small quantities.