INFLUENCE OF TEMPERATURE-GRADIENT TO SOLIDIFICATION VELOCITY RATIO ONTHE STRUCTURE TRANSFORMATION IN PULSED-LASER AND CW-LASER SURFACE-TREATMENT

The temperature gradient G, the solidification velocity R, and the G/R ratio are used in solid-liquid interface analysis. The critical G/R v alues characterizing the transitions from a planar front to a cellular structure, and from a cellular to cellular-dendritic structure during solidification are determined. The regularities of the rapid solidifi cation process are shown on the example of the titanium alloy subjecte d to boriding with a CW-laser. The G/R ratio and cooling rate values v ersus molted zone depth are analyzed. The dependence of the relative t ransition depth from cellular to cellular-dendritic structure on laser beam velocity is determined.