During the WAAM process, changes in the thermal field lead to local changes in layer height and material microstructure. The aim of this development activity is to develop in-process temperature monitoring tools to monitor the deposition process. This requires the development of remote measurement techniques that can be integrated with other sensors in a dynamic harsh environment with high temperatures, liquid metal, plasmas, hot gases and laser radiation. Thermal cameras have been used for this application, but issues with changing material emissivity have complicated measurements. We plan initially to look at dual-wavelength pyrometers as these are potentially less susceptible to emissivity effects.

The goal is to develop a wide range (200-1400 ⁰C) temperature measurement system which uses optical fibres to facilitate installation and allows the remote positioning of heat sensitive components. Two-wavelength pyrometers measure the radiation in two wavelength ranges and determine the temperature from the ratio of the intensity of the radiation in the separate ranges.