Selective laser melting of nickel superalloys for high temperature applications

• Main Author: Carter, Luke Nelson
• Published: University of Birmingham 2013
• Subjects: 669; TJ Mechanical engineering and machinery
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.577831

Selective Laser Melting (SLM) as a method of netshape manufacture is of growing interest within the aerospace industry. There is currently a lack of understanding of the influence of process variables on the integrity and properties of the as fabricated material. The research presented investigates the SLM fabrication of three nickel superalloys: Primarily CM247LC and CMSX486/IN625 as secondary alloys. CM247LC is Ni-base superalloy hardenable by the precipitation of the coherent \(\gamma\)'phase. It presents a particular challenge due to weld-crack susceptibility. This research aims to establish a processing route for CM247LC components via SLM: Parametric studies are presented to quantitatively assess the cracking behaviour based on microstructural observations; Hot Isostatic Pressing HIPping) has been investigated as a retro-fix solution to cracking; Electron BackScatter Diffraction (EBSD), MicroCT Tomography and microscopy have been used to characterise the SLM microstructure. The \(\gamma\)' evolution through the manufacturing stages (SLM & Heat Treatment) has been examined. Mechanical testing creep/tensile) was performed for comparison against cast material. Research was extended to two additional alloys: CMSX486 and IN625. Statistical design of experiments methodology was used to rapidly establish process parameters for these two alloys and assess them by mechanical testing. In conclusion a processing route capable of yielding fully dense material with a satisfactory \(\gamma\)' structure is presented; however, it involves significant post-fabrication processing which reduces the attractiveness of SLM. Further research is suggested, specifically into modelling and thermal measurement of SLM