Application of near infrared pyrometry for CW Nd:YAG laser welding of stainless steel and laser cladding of stellite

A bi-dimensional monochromatic and a 1-spot multiwavelengths pyrometers were applied for surface temperature monitoring in Nd:YAG continuous laser welding. The experiments were performed for stainless steel and titanium alloy applying variation of laser parameters: power, welding velocity, focalisation distance, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the dissimilar plates. Surface temperature evolution along and perpendicular to the welding seam and full temperature image versus laser action parameters were measured with the help of the bi-dimensional pyrometer. The dynamics of temperature gradients, transient periods and steady-state temperature distributions are analysed. The same approach is applied for Nd:YAG laser cladding of stellite on steel substrate. A new type of CCD based optical diagnostic tool has been applied for monitoring the particle in flight size and velocity.