Adaptive temperature control during transformation hardening with CO2-laser

Temperature-controlled laser transformation hardening is going to be established in industrial manufacturing of workpieces with complex geometries to ensure and increase the quality of the product as well as to reduce the influence of disturbances. The common structure of every process control is a feed-back loop which is built up here by a pyrometer, a controller and a flexible laser handling system. Specific problems occur in temperature-controlled transformation hardening of coated workpieces as the surface temperature ist not only determined by the process parameters and the thermophysical properties of the base material but also by those of the coating. An adaptive temperature control system (ATC) which estimates and controls the workpiece temperature underneath a coating is presented in this paper. The concept of the process identification and the control algorithm will be explained and experimental results will be reported.