A Numerical Simulation Of Heat And Mass Transfer For Bioceramic Coating On Condition Of Laser Cladding

In this paper,the physical and mathematic model of heat and mass transfer for the laser cladding bioceramic coating on TC4 have been carefully founded according to the FEM theory and characteristics of laser processing and coating powders. The three-dimension heat and two-dimension mass transfer has been numerically simulated with Matlab,a commercial FEM software.The numerical simulation show that the power density of 12.73- 15.27MW/m2 and scanning velocity of lO.Sm/s are the optimal parameters. The coating,interface and a small parts of the substrate are molten in 0.208 seconds during laser radiating. Depth of the molten pool is 0.5-0.9mm. The highest temperatures of outer coating and interface are 2481K and 2178K respectively. The Ca2+ ions can move into substrate at a depth of 0.193mm,and 0.191mm for P043- ions,furthermore,[Ti] can move into the coating at a distance of 0.145mm. The moving of Ca2+ and PO43- ions in the coating is helpful to the forming of calcium-phosphate bioceramics. The mass transfer of those two ions and [Ti] through interface results in a metallurgically bonding between coating and substrate.On the basis of above results,the mutual relationships among temperature,molten pool depth,mass transfer distance,parameters of the laser and properties of materials were carefully discussed. And the effects of heat and mass transfer on microstructures and properties of the coating were analyzed too. Finally,the experimental results of SEM,XRD,EDS,microhardness test accord with the above analysis,which implies the simulation performed in this paper is sound.