Experimental investigation on heat treatments of a MMC processed by LPBF for rocket engine thrust chambers

In recent years, more and more industries have been adopting Additive Manufacturing techniques, driven by the numerous advantages these technologies offer compared to traditional manufacturing methods. The aerospace sector is one of the industries that benefits the most: lead times and costs can be reduced while the performances of components can be enhanced by reducing mass through innovative designs. An interesting application of AM in the aerospace sector is the manufacturing of thrust chambers. These components have extremely complex geometries and need to be produced using high performance materials that can face extreme conditions. The object of this experimental thesis is a new material, Cu17-4PH, designed for the production of liquid rocket engine thrust chambers. Cu17-4PH is a Metal Matrix Composite realized by mixing 80% pure copper powder and 20% 17-4PH steel powder and processed by Laser Powder Bed Fusion. The aim of this work is to identify potential heat treatments that can improve the thermo-mechanical properties of the material, achieving a balance between hardness and thermal conductivity. A bibliographic research on heat treatments of 17-4PH and copper alloys is conducted to determine potential heat treatment temperatures. Additionally, Differential Scanning Calorimetry (DSC) analysis is performed to investigate the thermal behaviour of the material. Combining the results from the literature review and the DSC analysis, Cu17-4PH samples are heat treated at 600, 650 and 700 °C for various time, from 0,5 to 5 hours. Subsequently, Vickers microhardness test is performed to evaluate the hardness of the samples while their thermal conductivity is determined employing Hot Disk analysis and Laser Flash analysis. In addition, their elastic modulus is measured via Impulse Excitation Technique analysis and images of the microstructure, both before and after the heat treatments, are taken through an optical microscope.