Additive Manufacturing Process of Inconel Alloy 718

This article discusses the additive manufacturing process of Inconel alloy 718 and its potential as a viable business case. It covers the research methodology, experimental design, and results. The evaluation and generation of a database for EBWD-718 are also explored. The article delves into the discussion on manufacturability and industry acceptance.

ADVANCE MANUFACTURING
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Abstract
Remarkable contributions have been attained in the recent past as far as the additive
manufacturing technology is concerned. The advancements in the electron-beam based AM and
laser equipment with the use of wire feed, powder injection or powder bed systems have been
have been able to reap from advancement in software programs in converting sophisticated CAD
models into parts that are Digitally Manufactured. This presentation discusses additive
manufacturing process of Inconel alloy 718 and the chances of changing additive manufacturing
into a business case that is viable.

Contents
Abstract.......................................................................................................................................................2
Introduction.................................................................................................................................................4
Research problem statement........................................................................................................................4
Research Methodology and Experimental Design & Results......................................................................5
Evaluation and Generation of Data base for EBWD-718........................................................................6
Discussion.................................................................................................................................................10
Conclusion.................................................................................................................................................13
References.................................................................................................................................................15

ADDITIVE MANUFACTURING PROCESS OF NICKEL BASED SUPERALLOYS SUCH
AS INCONEL 718, INCONEL 625
Introduction
Additive Manufacturing can be described as group terms for the technologies of manufacturing
that in a process that is automated generate 3-D objects either as whole or in part directly from
CAD data of 3D by the successive material addition excluding the use specialized equipment and
tools. Additive manufacturing is quite a new technology that has a history of spanning of about
40 years as such a length of time is not comparable to the amount of time that the formative and
subtractive shaping technologies have taken in the manufacturing industry [1].
Research problem statement
Nevertheless, there have been significant contributions experienced in the recent past as far as
the development of electron beam based equipment of AM with powder injection, wire feed
systems or powder bed are concerned and the associated benefits as a result of advancements in
the software programs that are used in the conversion of sophisticated CAD models into
Digitally Manufactured components
The need to attain such demands as tight costs, quality as well as schedule have seen AM
technology as one of the most widely accepted technologies for use in such industries as the
aeroscope industry [2]. Such business case factors besides the precise requirements of property
and the complexity level of part-family have a strong influence on choice of recommended AM
process. Some of the process of additive manufacturing are idea for small, sophisticated
geometry, Free-Form Fabrication components that have Net shapes that are tight tolerant.
Others, under programming by multi-axis or robotic machines may span the range of part size all
the way to FFF bigger parts or even feature-additions. The finish of the surface from numerous

additive manufacturing processes on the products still remains at Near-Net-Shape. A significant
aim is minimizing from any form of post processing including machine or even surface finishing
in the achievement of the Net-Shape ability within tolerances of surface finish of the design part.
Research Methodology and Experimental Design & Results
There is an avalanche of probable additive machining materials, design property as well as part
quality standard requirements, Thus, the methodology of down-selection chain an additive
manufacturing chances into a profitable business case requires to be discerning in terms of cost
effectiveness and coverage [3]. The metallurgical approach adopted as an aspect of current work
methodology aimed at defining a standard shape that would be made by every additive
manufacturing process that is considered. INCONEL alloy 718 was the material of choice even
though 625 as well as co-based alloys have as well been studied. 3.15 inches which is equivalent
to 80 mm-sided cube was used as the standard shape that allow X, Y, Z as well as Z-interface
orientations to be featured and comparisons made using the recommended specimens of ASTM.
Evaluation was done on the additive manufacturing alloy 718 cubes for such properties as:
 Capability to form shapes
 Quality and microstructure (inclusions and porosity among others)
 Mechanical features (dependent on time and monotonic)
Four processes which were relatively mature were tested so as to down select a process that was
suitable and was as per the shape forming, business case as well as structure or property forming
criteria for a selected part family. The processes of additive manufacturing used were among
them Electron Beam Wire Deposition, Laser Powder Deposition, Direct Metal Laser Sintering as

well as Gas Metal Arc Welding [4]. The Electron Beam Wire Deposition was one such process
that was examined to greater depth and found out:
 A data-base for property by which comparison may be other for other processes
 A methodology which was then picked for the other additive manufacturing processes
Figure 1: (i) B-Ring with deposits of EBWD-718 (ii) C-Ring end-on having deposit of double
flange EBWD-718 (iii) C-Ring laid flat. Source Körner, 2016
Evaluation and Generation of Data base for EBWD-718
Studies were earlier contacted on this AM process as a component of the Materials Affordability
Initiative. EBWD-718 was extensively characterized further in this study using the methodology
of add-on cube in the establishment of a minimum design space data base for a specific part. The
diagram above indicates a basic test assembly of a rolled AMS 5663 using EBWD cubes, flanges
as well as cylinders that simulate a case component that has a generic structure. The thickness of
the rolled ring wall was higher as compared to that of the typical walls since the main concern in
this initially involves the characterization of the mechanical features as well as the structure of
EBWD-718 deposits/se as well as interfaces using wrought AMS 5663 alloy [5].
The progression plan running from the deposit to the test specimen is as shown in the figure
below. Every deposit was heat treated to the specifications of the wrought alloy since the ring

was the main segment. The obtained data of EBWD was compared against the one for a typical
cast for example AMS 5383 as well as a wrought 718 alloy in that order. The database would
thus be at disposal when handling the challenging aspects of manufacturability of generating
these casings that have thinner walls that are typical of the real parts.
Figure 2: (a) Deposited EBWD-718 (b) Machine cube, (c) Orientations of specimen. Source
Körner, 2016
The EBWD database was inclusive of notch-smooth, creep, tensile stress rupture as well as
specifically the matrices of LCF. The general trend noted in all the mentioned features in
comparison with cast and wrought EBWD-718 respectively are shown in figure below. The
means of the properties of EBWD-718 were generally between as compared with cast while
closer to that of wrought alloy 718. The data contained the joint mean of X, Y, Z as well as Z-
interface orientation of the cubes used.

Figure 3: UTS & YS features of EBWD-718 against wrought & cast. Source Körner, 2016
Nevertheless, differences in the microstructure between the various orientations are as result of
the EBWD process directionality as shown in the below figure. Such differences in the
orientation in the structure alongside the possible impacts on porously may have an influence on
the features. In making a summary of such impacts on the current work on EBWD-718 it was
established that the orientations of X as well as Y were of similar monotonic features [6]. The
properties of LCF of the X and Y directions as well were found to be falling within relatively the
same trends with the minor differences between X alongside the relatively lower Z-direction
features did not look significant.
More scatter was noted in Z-interface features even though in general, the probability plots for
each of the LCF data or combined data were in harmony with the log-normal distributions
besides showing the orientations of the AM materials to be of insignificant impacts on the LCF
features as demonstrated in the figure below. Hence, all the data of EBWD as extracted from
both the X as well as Z orientations may be joined for analysis of the performance.
Figure 4: Cube macrostructure of EBWD-718 against deposition mode or test orientation. Source
Körner, 2016

In as much as the conclusion on the effects of orientation was reached for EBWD data, an
assumption cannot be made for the remaining AM processes which have various modes of
additive manufacturing, controls as well as environments. The characterization of the orientation
impacts need to be made in reference to the process of additive manufacturing, the requirement
of the respective property of Design space as well as the component build material.
EBWD-718 material that was used in this test was very clean as anticipated from a process that
is of high vacuum such that any orientation impacts related to inclusion may be assumed [7]. The
differences in the shape as well as size of the microstructure grain between the various
orientations would be of more impacts on the features.
Figure 5: Log-normal Actual/Projected distribution of LCF for (a) X orientation (red squares)
and Z (dark circles) & (b) joined X and Z data. Source Körner, 2016
As the layers undergo deposition, re-melting of the layers beneath take place and weld deposit
root may break through one or more of the layers as determined by heat input levels as released
from the electron beam. Some delineation between the weld layers through the regions of
interface of nucleations as well as re-melting of the fine grains is shown in the figure below. Re-
melting as well as formation of grain boundary through the past deposit is shown in figure (a)
while figure (b) represents a montage demonstrating weld deposit penetration as well as weld-

on-weld deposits into interface using AMS 5663 plate of substrate. Normal boundary of grain as
well as delta needles intra-granular precipitation in deposits upon subsequent STA [8].
Figure 6: Grain boundary formation & re-melting at overland EBWD-718 root pass micrograph.
Source Körner, 2016
Discussion
Even though a limited overview, the screening findings allowed for the comparison as well as
contrasting of additive manufacturing processes alongside noting some of the sections that called
for enhanced development. Following the metallurgical summary, consideration into the other
drivers of technology among them cost, performance, quality as well as schedule are needed in
the process of selecting on the appropriate process or products of additive manufacturing for a
given part of gas turbine.

Figure 7: Variation in apparent density between various AM process products. Source Abe &
Sasahara, 2016
Manufacturability: The advantages of attaining the mentioned drivers of technology may only be
noted when the chosen additive manufacturing process has the desirable manufacturability.
Failing to meet such a criterion is normally the downfall of any new process as has been noticed
from experiences [9]. Some of the guidelines for additive manufacturing which are mostly non-
metallurgical include:
 Component that is of low to medium risk
 Manufacture and/or repair
 Relevant database as well as experience in manufacturing
 Production quantity component that ranges from low to medium
 Monitoring, source approval as well as qualification of supplier
 Lowered Buy-to-Fly ratio
 The process has to be recorded, reproducible and robust
 Initial deferment from thin wall components
 Using work horse alloys initially including alloy 718, 625 as well as Ti-6-4
 Preference of standalone components as compared to components of sub-assembly
The development of feedback, closed loop control during alloy addition of the melt-pool in the
automation of the process of additive manufacturing in real time may offer manufacturing some
degree of fidelity. It forms one of the active areas for experimental research as well as modelling

Figure 8: Porosity variation image analysis between various AM process products. Source Abe &
Sasahara, 2016
Industry acceptance: Generally, there is need for the specifications as well as standards of
AMS/ASTM to be of conformity, risk reduction as well as repeatability features for additive
manufacturing to be widely accepted in the industry within as well as among the various
companies. Committee F24 has been established by ASTM regarding additive manufacturing
technologies that are coming up with standards via numerous sub-committees handling the
specific parts respectively [8].
Company acceptance: Every OEM would require conducting a review of the filed as well as
examining numerous additive manufacturing processes with the aim of determining the
limitations, capabilities as well as building high confidence levels needed for the company to
accept. The introduction of a process that is relatively new for sample additive manufacturing or
even the use of familiar alloys among them 718 needs that the featured be grouped against the
databases of the internal design since the behavior of the product is influenced by the process,
orientation, heat treatment as well as chemistry.

The requirements on the performance as well as quality tend to be relatively stricter for the case
of aeroscope super alloys in comparison with the general applications of alloys in engineering.
The investments must be justified by the cost benefit analyses with the production pull levels as
well as the risks being the major determinants in decisions of any business cases. Internal
specifications on the materials as well as processes of additive manufacturing should be
rationalized and developed to make the content as well as number simpler.
There should be establishment of Engineering Standard Work that is incorporative of design for
additive manufacturing [10]. This method may offer guidance to the designer with capitalization
on the unique characteristics which are offered by additive manufacturing in the production of
parts that have highly short lead-times which are challenging, intensive in terms of labor process
or even not possible in the manufacturing through the use of conventional approaches.
Conclusion
The choice on an appropriate option for additive manufacturing is influenced strongly by the
scale, level as well as cost of part-family sophistication as well as the products or process
metallurgical factors; all of which must be taken into consideration to change an additive
manufacturing chance into a business case that is viable. The Z-orientation features were
generally relatively lower that the X(Y) additive manufacturing processes deposition even
though slightly higher for the case of powder bed sintering. The quality of the EBWD-718
product was specifically higher and almost the same as that of wrought and small significant
effects of orientation on the analyses of performance. The processes of additive manufacturing
are at the moment at various levels with regard to the dimensional control and shape owing to the
operating parameters that are intrinsic and linked to the localized solidification and control of
melt. In this study, the order of the decrease in shape definition was

DMLS>LPD>EMBD>GMAW. The aforementioned rigor as well as unified AMS/ASTM
standards and specifications are need by the company as well as industry for the purposes of risk
reduction, conformity and repeatability for additive manufacturing to be adopted within and
among various companies.
References
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using wire and arc-based additive manufacturing. Precision Engineering. 2016 Jul 1;45:387-95

[2]. Denlinger ER, Heigel JC, Michaleris P, Palmer TA. Effect of inter-layer dwell time on
distortion and residual stress in additive manufacturing of titanium and nickel alloys. Journal of
Materials Processing Technology. 2015 Jan 1;215:123-31
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layer laser additive manufacturing of Ni-based alloy on cast iron. International Journal of Heat
and Mass Transfer. 2017 Aug 1;111:709-22
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Materialia. 2016 Sep 15;117:371-92
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Idell Y, Williams ME. Application of finite element, phase-field, and CALPHAD-based methods
to additive manufacturing of Ni-based superalloys. Acta materialia. 2017 Oct 15;139:244-53
[6]. Kenney PM, Lindley DE, inventors; General Electric Co, assignee. Additive manufacturing
method and apparatus. United States patent application US 10/124,408. 2018 Nov 13
[7]. Körner C. Additive manufacturing of metallic components by selective electron beam
melting—a review. International Materials Reviews. 2016 Jul 3;61(5):361-77
[8]. Shiva S, Palani IA, Mishra SK, Paul CP, Kukreja LM. Investigations on the influence of
composition in the development of Ni–Ti shape memory alloy using laser based additive
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[10]. Wang Z, Denlinger E, Michaleris P, Stoica AD, Ma D, Beese AM. Residual stress mapping
in Inconel 625 fabricated through additive manufacturing: Method for neutron diffraction
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