Laser rapid forming (LRF) is a new manufacturing technology, which has been
developed on the basis of multi-layer laser cladding. In the LRF process, the microstructure has
important effects on the mechanical properties of the partsbut the control of microstructure is a
problem. In this study, the influences of crystallography orientations of substrate and profile of
solid/liquid interface on microstructure were discussed. Further, with the combining of the
columnar to equiaxed transition (CET) model during alloy solidification, the growth law of
microstructure of Rene88DT alloy was established. It has been found that the temperature gradient
was lowest and the solidification velocity was greatest at the solid/liquid interface of the tail of
molten pool, and hence the CET occurs easily at this position. The temperature measurement
system of molten pool was developed by using a two-color infrared thermometer in this study. With
the measurement of temperature gradient of the tail of molten pool by using a two-color infrared
thermometer, the process parameters of laser multi-layer cladding were optimized. Finally,
directional solidification even single crystal was achieved in laser multi-layer cladding.
Impact of measuring distance and exposure to cold outdoor environment on the temperature measurement using a non-contact infrared thermometer
