A Single Crystal Process Window for Electron Beam Powder Bed Fusion Additive Manufacturing of a CMSX-4 Type Ni-Based Superalloy.

Julian Pistor,Christoph Breuning,Carolin Körner

doi:10.3390/ma14143785

Julian Pistor, Christoph Breuning + Show 1 more

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https://doi.org/10.3390/ma14143785

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Journal: Materials	Publication Date: Jul 6, 2021
Citations: 19	License type: CC BY 4.0

Affiliation: University of Erlangen-Nuremberg

Abstract

Using suitable scanning strategies, even single crystals can emerge from powder during additive manufacturing. In this paper, a full microstructure map for additive manufacturing of technical single crystals is presented using the conventional single crystal Ni-based superalloy CMSX-4. The correlation between process parameters, melt pool size and shape, as well as single crystal fraction, is investigated through a high number of experiments supported by numerical simulations. Based on these results, a strategy for the fabrication of high fraction single crystals in powder bed fusion additive manufacturing is deduced.

Highlights

Window for Electron Beam PowderSingle crystal Ni-based superalloys are state-of-the-art materials for high-temperature applications in turbine blades at both high temperatures and high mechanical loads
Typical single crystal alloys, such as CMSX-4 developed by Cannon Muskegon, are optimized for casting processes according to the Bridgman process [2,3]
Starting with an fine columnar (FC) microstructure for 5.5 J/mm2 the center of the sample begins to coarsen with increasing energy input

Summary

Introduction

Window for Electron Beam PowderSingle crystal Ni-based superalloys are state-of-the-art materials for high-temperature applications in turbine blades at both high temperatures and high mechanical loads. A so-called grain selector helix is introduced in the shell mold to select only one well-oriented grain of the initial columnar grain structure [6] This production route incorporates some major drawbacks like the lack of part complexity and the high amount of residual elemental segregation, leading to expensive and time-consuming post-processing [7]. Several groups already have investigated this type of nonweldable casting alloys by powder-based additive manufacturing [8,9,10,11,12,13,14], where elemental segregation is much smaller due to high solidification rates [15] Since these alloys are not optimized for additive manufacturing, processing is challenging. Recent studies have shown that apart from alloy modifications [20,21,22], either a high amount of high angle grain boundaries or no high angle grain boundaries at all (single crystalline, SX) are necessary to process these alloys without cracks [8,23]

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