Fiber Bragg Grating Sensor Embedding and Temperature Monitoring in Die-Casting Molds Using Directed Energy Deposition

Abstract Die casting is a widely used precision casting method. In die casting, the injection and mold temperatures affect the fluidity during casting and cooling. However, because the temperature characterization of die-casting molds is conducted fragmentarily using thermocouples and thermal imaging cameras, a fundamental solution is needed to ensure the reliability of the temperature data. In this study, real-time multipoint temperature measurements were conducted by embedding a seamless tube into an AISI-H13 specimen using Directed Energy Deposition. The interface of the deposited layer and H13 substrate was subsequently observed via Scanning Electron Microscope (SEM). Real-time temperature monitoring according to the embedding depth was conducted by inserting fiber Bragg grating (FBG) sensors into the specimen, followed by mechanical property testing. The temperature sensitivity and stabilization did not significantly differ within the 1-3 mm depth range, thus confirming that the temperatures at multiple points could be measured in real time. The SEM images revealed no porosity at the interface. Compared with that of the original material, the tensile strength of the deposited layer improved. Furthermore, because the interface hardness of H13 exceeds that of 50 HRC, which is commonly used in die casting, FBG sensors could also be applied to industrial die-casting molds.