Using optical diagnostics to determine the melt temperature field in layer-by-layer laser alloying of metal powder

The results of application of optical diagnostics in the estimation of the temperature field at the melt surface in layer-by-layer laser alloying of metal powder are presented. It is demonstrated that surface concavity induced by the thermocapillary effect upon nonuniform heating may distort pyrometry data considerably. The use of external illumination provides an opportunity to determine the shape of the melt surface. The obtained minimum estimate of the temperature gradient in the metal region affected by laser radiation is 2.8 × 10⁴ K/cm.