Real-time detection of cooling rate using pyrometers in tandem in laser material processing and directed energy deposition

•Real-time monitoring of cooling rate using pyrometers in tandem was reported.•Surface temperature and cooling rate variation in laser remelting was studied.•Molten pool size and cooling rate variation in additive manufacturing was studied. A novel method of monitoring cooling rates in real-time using two pyrometers arranged in tandem has been demonstrated. First pyrometer monitors the temperature at the center of the molten pool, second monitors the temperature at its tailing end. The difference in two pyrometer signals provides the temperature gradient at 1 kHz frequency from which cooling rate is determined in real-time using Arduino interface. Effectiveness of this method in real-time monitoring of cooling rate during laser remelting and additive manufacturing by directed energy deposition with varying process parameters and layer number is demonstrated.