Abstract
Aluminum test pieces with thermally-sprayed surface layers of Si, Fe, Cu and Ni in a thickness range of 30-200, um were remelted by CO2 laser radiation at varying power densities of 3.8×103-4.2×104 w/cm2. The metallurgical structure of the alloyed surface layers was examined by optical microscopy. It was found that the melting and alloying behavior of the surface layers was governed by the relationship between the power density and the thickness and properties of the sprayed materials. Macrosegregation due to power density differences was also observed in the alloyed layers. In view of metallurgical structure, the following hypothesis was made about the alloying process. It is assumed that the aluminum base metal began to melt at the interface with the sprayed layer due to the heat conducted through the latter. The sprayed element still in solid phase then dissolved into the molten pool of Al due to diffusion to produce the alloyed layer. Convection induced by the density difference worked to promote alloying. The alloying process was simulated using ABAQUS version 4.7, a general purpose Finite Element Method (FEM) code for unsteady state thermal diffusivity analysis. Good agreement was seen between the simulation results and experimental data.
