@Article{icces.2023.010342,
AUTHOR = {Zhenan Zhao, Weizhu Yang, Lei Li, Shouyi Sun, Yan Zeng},
TITLE = {High-temperature	Fatigue	Performance	of	Laser	Directed	Energy	 Deposited	Ni-Based	Superalloy	Under	Different	Heat	Treatment},
JOURNAL = {The International Conference on Computational \& Experimental Engineering and Sciences},
VOLUME = {25},
YEAR = {2023},
NUMBER = {3},
PAGES = {1--2},
URL = {http://www.techscience.com/icces/v25n3/53855},
ISSN = {1933-2815},
ABSTRACT = {The	hot	section	components	are	usually	in	service	under	cyclic	loading	in	an	extreme	working	environment	with	
high	rotational	speed	at	high	temperatures,	which	is	prone	to	fatigue	failure.	It	is	reported	that	fatigue	related	
failures	have	accounted	for	over	50%	of	all	failures	of	hot	section	components.	Consequently,	fatigue	related	
failure	at	high	 temperature	is	one	of	 the	most	important	 factors	 that	shortens	 the	service	life	of	hot	section	
components.	 Ni-based	 superalloy	 GH4169,	 similar	 as	 Inconel	 718	 (IN718),	 is	 a	 γ′′	 and	 γ′	 precipitation	
strengthened	 alloy.	 For	 decades,	 GH4169	 superalloy	 keeps	 being	 an	 important	 material	 in	 hot	 section	
components	of	gas	turbines.	It	has	been	widely	used	for	producing	the	hot	section	rotating	components	of	aeroengines,	gas	turbines	and	nuclear	power	plants	owing	to	its	high	strength,	creep	resistance	at	high	temperature	
(up	to	650	°C).<br/>
However,	Ni-based	superalloys	are	well	known	for	their	difficulty	in	machining	due	to	its	high	hardness	and	
toughness.	Therefore,	one	of	the	alternative	manufacturing	processes	is	Laser	Directed	Energy	Deposition	(LDED),	being	one	of	additive	manufacturing	(AM)	techniques.	In	this	process,	the	laser	beam	creates	a	melt	
pool	on	a	substrate	material,	into	which	the	metal	powder	is	blown	by	the	inert	gas	flow	from	the	co-axial	
powder	nozzle	at	the	same	time.	Moving	the	laser	beam	together	with	the	powder	nozzle	will	create	a	weld	
track,	and	multiple	overlapping	weld	tracks	leads	to	a	layer	while	multiple	layers	can	build	a	3D	structure.	In	
recent	years,	the	L-DED	process	has	attracted	full	attention	and	been	applied	in	modern	industries	such	as	
fast	prototyping,	coating,	light-weight	optimization	etc.,	due	to	its	ability	to	fabricate	geometrically	complex	
components	in	near-net	shape,	and	to	repair	damaged	parts,	which	is	of	high	interest	for	the	production	and	
maintenance	of	hot	section	components.	In	this	case,	understanding	the	fatigue	properties	of	laser	directed	
energy	 deposited	 (L-DEDed)	 Ni-based	 superalloy	 is	 expected	 to	 be	 a	 major	 concern in	 adaptation	 of	 AM	
technology	into	the	turbine	industry.<br/>
This	study	investigates	the	fatigue	behavior	of	GH4169	Ni-based	superalloy	at	650	°C	fabricated	by	L-DED	
and	 proposes	 an	improved	 high-temperature	 fatigue	 resistance	 by	 regulating	 the	 heat	 treatment.	 To	 this	
purpose,	three	conditions	of	solution	and	aging	heat-treated	fatigue	specimens,	namely	980STA,	980S5hDA,	
and	 1050STA,	 were	 assessed	 by	 advanced	 material	 characterization	 technique	 including	 TEM,	 EBSD	 etc.	
Results	show	 that	 the	 fatigue	resistance of	 the	L-DEDed	GH4169	with	different	heat	 treatments	is	mainly	
determined	by	the	short	crack	propagation	behavior,	which	is	influenced	by	the	combined	effect	of	grain	size	
and	morphology.	Finer	grains	with	less	 texture	strength	of	 the	1050STA	 fatigue	specimen	has	 the	longest	
short	crack	propagation	life,	while	a	cluster	of	large	grains	oriented	to	the	<001>	orientation	of	980S5hDA	
leads	to	the	most	significant	short	crack	propagation	rate.	Besides,	the	long	fatigue	crack	propagation	under	
the	effect	of	strength	and	precipitates	also	minorly	influence	 the	 fatigue	resistance.	The	microstructure	of interconnected	 precipitates	including	 the	 needle-like	 δ	 phase	 and	 slender-stripe	 shaped	 Laves	 phase	in	
980STA	and	1050STA	specimens	has	a	better	hindering	effect	on the	fatigue	crack	propagation	than	that	of	
the	discrete	δ	phase	in	980S5hDA	specimen,	and	the	1050STA	specimen	has	the	best	strength.	As	a	result,	
the	 980S5hDA	 specimen	 has	 the	worst	 fatigue	 performance,	while	 the	 1050STA	 specimen	 has	 the	 best.	
Compared	to	longer	solution	time,	higher	solution	temperature	can	improve	the	fatigue	resistance	of	the	LDEDed	GH4169.},
DOI = {10.32604/icces.2023.010342}
}