Selective Laser Melting Fabrication of the Nickel Base Superalloy CMSX486: Optimisation of Process Parameters using Image Analysis and Statistical Methods

Research output: Contribution to journalArticlepeer-review

Colleges, School and Institutes

Abstract

Purpose
Selective Laser Melting (SLM) of high temperature nickel base superalloys has had limited success due to the susceptibly of the material to solidification and reheat cracking. The aim of this study is to optimise the SLM process parameters for CMSX486 in order to produce a ‘void free’ (fully consolidated) material, whilst reducing the cracking density to a minimum providing the best possible as fabricated material for further post processing.

Design/methodology/approach
Samples of CMSX486 were fabricated by SLM. Statistical DOE (Design of Experiments) using the response surface method was used to generate an experimental design and investigate the influence of the key process parameters (laser power, scan speed, scan spacing and island size). A stereological technique was used to quantify the internal defects within the material, providing two measured responses: cracking density and void percent.

Findings
The analysis of variance (ANOVA) was used to determine the most significant process parameters and showed that laser power, scan speed and the interaction between the two are significant parameters when considering the cracking density. Laser power, scan speed, scan spacing and the interaction between power and speed, and, speed and spacing were the significant factors when considering void percent. The optimum setting of the process parameters that lead to minimum cracking density and void percent was obtained. It was shown that the nominal energy density can be used to identify a threshold for the elimination of large voids; however it does not correlate well to the formation of cracks within the material. To validate the statistical approach, samples were produced using the predicted optimum parameters in an attempt to validate the response surface model. The model showed good prediction of the void percent; however the cracking results showed a greater deviation from the predicted value.

Originality/value
This is the first ever study on SLM of CMSX486. The paper shows that provided that the process parameters are optimised, SLM has the potential to provide a low cost route for the small batch production of high temperature aerospace components.

Details

Original languageEnglish
JournalRapid Prototyping Journal
Volume21
Issue number4
Publication statusPublished - 2015