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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.
Supervisor(s):Wu, Xinhua and Attallah, Moataz
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Metallurgy and Materials
Subjects:TJ Mechanical engineering and machinery
Institution:University of Birmingham
ID Code:4410
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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