Engineering Literature Review: Ultrasonic Vibration-Assisted LENS 718

This literature review investigates the application of Ultrasonic Vibration-Assisted Laser Engineered Net Shaping (UV-A LENS) in the fabrication of Inconel 718 parts. The study focuses on the benefits of UV-A LENS, including the potential to reduce fabrication defects such as porosity, and improve mechanical properties. The review explores the current research on UV-A LENS, including the use of ultrasonic vibration in the solidification processes of melting metal and its effects on the microstructure. It highlights the importance of Inconel 718 in the aerospace and industrial sectors due to its superior properties and discusses the challenges related to fabrication defects and heterogeneous microstructures. The paper emphasizes the need for further research to understand the influence of ultrasonic vibration on the mechanical properties of LENS fabricated Inconel 718 parts. The review synthesizes existing literature to identify a research gap and justify the need for further investigation into the application of UV-A LENS in manufacturing and repairing high-value metal parts.

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Ultrasonic vibration assisted Laser Engineered Net Shaping
Laser additive manufacturing has actually emerged as a competitive direct techniques that are
utilized in fabrication of those structures of metals that have very complex parts. The process
that is involved exploits its benefits that include excellent stability, density of the power is high
as well as being easy to control [1]. Considering these admirable properties, the technique has
been underutilization. The technique of LAM has been basically grouped into power bed fusion
mode and the mode of laser beam deposition. When compared with the powder bed fusion, the
additive manufacturing including the selective laser melting which commonly referred to as
SLML as Engineered net Shaping[3]. The beam deposition by using direct laser has the
advantages of having its application in the part repairing, high part building efficiency and
finally high power utilizing efficiency. This clearly shows that the LENS has been applied as one
of the main technologies in the fabrication and repairing of the functional and high value-added
parts of the metals [4].
The increased volume of the molten pool by the use of which results in porosity is a challenging
process in this particular technique application. In all the processes of the applications of LENS,
there is usually use of the high energy laser beam in the creation of a molten pool with a
particular substrate [12]. In the process, there is continuous delivery of the powder into the pool
which is molten by a beam of flowing inert gas using the coaxial nozzle [7]. This results in an
increased volume of the molten pool. After the molten pool left the radiation of a laser beam, it
begins to solidify. As the head of the deposition moves along the path for tracking, there is
deposition of the first layer on the substrate. It is after this particular process that the head will
improve by one layer thickness to the next position so as to allow for the deposition of the next

layer. Several similar processes will be repeated many times before the goal of three-dimensional
structures is accomplished by the layer by layer building process [6].
A previous investigation was carried out by the researchers in the ultrasonic vibration- assisted
(UV-A) LENS manufacturing of 17-4 PH to produce parts of stainless steel. The results that
were obtained indicated a reduction in the fabrication defects through the use of the ultrasonic
vibration [5]. This actually led to the improved tensile properties as well as microhardness of the
components. Also, there was the achievement of larger microhardness and finer microstructure in
the application of n UV-A laser metal deposition in the treatment of the stainless steel 316L [8].
The other similar studies on the ultrasonic vibration enhanced the bonding strength of the
coating. One of the important applications that have been considered relevant focuses on the
component of the aircraft turbine who’s manufacturing process and repair are done by the use of
nickel-based super alloys [13]. Considering that most of these super alloys are expensive as well
as exhibiting poor machinability, the use of LENS method allows for the reduced material
wastages hence leading to the reduced or decreased cost of manufacturing as well as improved
productivity. There is a type of precipitation nickel-based super alloy that is used for hardening
called Inconel 718[14].
In order to homogenize material dispersion and suppress cracks, the researchers have proposed
the use of several techniques including ultrasonic vibration-assisted LENS. By optimizing the
parameters for the processes, the scholars successfully fabricated the net-shaped and dense
structure of Al2O3 by LENS. This was for the case of the investigation that was being carried
out on the ceramic material of aluminum material [10]. The result indicated that the toughness,
as well as the microhardness of the LENS fabricated parts, could be compared to those made by

the conventional processes of manufacturing. Taking into account the periodical positive-
negative pressures, caustic streaming has been targeted for quite sometimes. This is because it is
known to facilitate the transient cavitation, pulsation, growth formation as well as the collapse of
the micro-sized bubbles. Also, such influences are considered beneficial for the cases of
homogenizing dispersion of the material, thermal gradient smoothing out and finally thermal
stress reducing cracks refining grains [11].
This particular material has been identified as the best material component in the repair of the
turbine as well as its manufacture as a result of its superior properties like being carrion resistant,
perfect oxidation resistance, and high fatigue strength at higher temperatures. There has been an
attraction of the interest in the application of Inconel 718 in both the field of academia and
industrial sectors. There has been several investigation processes carried out to evaluate
mechanically as well as the microstructure properties of the parts with LENS fabricated Inconel
718[15].
It is important to note that the defects of fabrication including cavities, pores, and heterogeneous
microstructure are usually results of the induction process. The induction process is usually
considered detrimental to the qualities of the parts as well as mechanical characteristics of the
parts of LENS fabricated Inconel 718. It is, however, regrettable that there are no reported
investigations that have been carried on the parts of UV-A LENS of Inconel 718. Despite these
shortcomings, the technique has continued to a challenge in the industry due to lack of
information from literature sources on the effects of ultrasonic vibration on the metal parts
during such treatment methods [10]. There has been an effective use of the Ultrasonic Vibration
in the solidification processes of melting metal including arc welding, casting among others.

There are several nonlinear effects that are caused by the direct input of the ultrasonic vibrations
like cavitation and streaming.
Such effects are responsible for the reduction in the porosity as well as homogenizing of the
microstructure of additively manufactured components [12]. There is a need for the study of the
influence of Ultrasonic Vibration on the parts of the metals that are LENS fabricated before the
processes of heat treatment. In this particular paper, there has been the utilization of the UV-A
LENS process in the fabrication of the parts of Inconel 718 with the aim of having a reduction or
the possible elimination of the parts defects.

References
[1] S.H, Alavi and S.P, Harimkar. Melt expulsion during ultrasonic vibration-assisted laser
surface processing of austenitic stainless steel. Ultrasonics,[Nov 2015]
[2] S.H, Alavi and S.P, Harimkar. Ultrasonic vibration-assisted continuous wave laser surface
drilling of materials. Manufacturing Letters, 2015;4, pp.1-5.
[3] S.H. Alavi, C. Cowell,.and , S.P.Harimkar. Experimental and finite element analysis of
ultrasonic vibration− assisted continuous-wave laser surface drilling. Materials and
Manufacturing Processes,[Sep 2017]
[4] W. Cong, and, F. Ning. A fundamental investigation on ultrasonic vibration-assisted laser
engineered net shaping of stainless steel. International Journal of Machine Tools and
Manufacture, [Dec 2017]
[5] M .Eslamian and F. Zabihi. Ultrasonic substrate vibration-assisted drop casting (SADC) for
the fabrication of photovoltaic solar cell arrays and thin-film devices. Nanoscale research
letters, [July 2015]
[6] Y. Hu, F, Ning, W. Cong Y .Li, X. Wang. and H. Wang, Ultrasonic vibration-assisted laser
engineering net shaping of ZrO2-Al2O3 bulk parts: Effects on crack suppression, microstructure,
and mechanical properties. Ceramics International, 44(3), [May 2018]

[7] Y. Jeon, H. Park, and W. Lee. Current research trends in external energy assisted
machining. International Journal of Precision Engineering and Manufacturing,[March 2013]
[8] C. Li; Zhang,F. Meng, B., Liu, L. and X. Rao, X.,. Material removal mechanism and
grinding force modeling of ultrasonic vibration assisted grinding for SiC ceramics. Ceramics
International, [July 2017]
[9] M .Li, B Han, Y Wang, L Song, and L.Guo, . Investigation on laser cladding high-hardness
nano-ceramic coating assisted by ultrasonic vibration processing. Optik, [ July 2016]
[10] F.Ning, and W.Cong. Microstructures and mechanical properties of Fe-Cr stainless steel
parts fabricated by ultrasonic vibration-assisted laser engineered net shaping process. Materials
Letters,[August 2016]
[11] F.Ning,F. Hu, Z; Liu, W. Cong, Y.Li, and X.Wang; Ultrasonic vibration-assisted laser
engineered net shaping of Inconel 718 parts: a feasibility study. ; Procedia Manufacturing, [Nov
2017].
[12] F.Ning,Y. Hu. Z.Liu, X. Wang, Y. Li, and W. Cong,; Ultrasonic vibration-assisted laser
engineered net shaping of Inconel 718 parts: microstructural and mechanical characterization.
Journal of Manufacturing Science and Engineering,[May 2018]
[13] J.Y.Shen, J.Q. Wang, B. Jiang,X. and X.P.Xu, Study on the wear of diamond wheel in
ultrasonic vibration-assisted grinding ceramic. Wear,[Jan 2015].
[14] C. Zhang, P.Feng, and J.Zhang,. Ultrasonic vibration-assisted scratch-induced
characteristics of C-plane sapphire with a spherical indenter. International Journal of Machine
Tools and Manufacture, [June 2013].

[15] S. Zhou, G. Ma, W. Dongjiang, D. Chai, and M. Lei,2018. Ultrasonic vibration assisted
laser welding of nickel-based alloy and Austenite stainless steel. Journal of Manufacturing
Processes, 31, pp[Jan 2018].