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# Selective laser melting of nickel superalloys for high temperature applications

Carter, Luke Nelson (2013)
Ph.D. thesis, University of Birmingham.

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## Abstract

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

Type of Work: Ph.D. thesis. Wu, Xinhua and Attallah, Moataz Colleges (2008 onwards) > College of Engineering & Physical Sciences School of Metallurgy and Materials TJ Mechanical engineering and machinery University of Birmingham 4410
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