Influence of Filler Metals in the Control of Deleterious Phases During the Multi-pass Welding of Inconel 718 Plates

doi:10.1007/s40195-014-0185-5

Abstract

Abstract:

The present study reported the effect of filler metals on the microstructure and mechanical properties of pulsed current gas tungsten arc-welded Inconel 718 plates. Two different filler metals such as ERNiCr-3 and ERNiCrMo-4 were employed for welding Inconel 718. The primary objective of this study is to suppress or eradicate the deleterious phase such as Laves or δ (delta) which is considered to be detrimental to the weld properties. Microstructure examination corroborated the presence of unmixed zone at the HAZ for both the weldments. Tensile test trials envisaged that ERNiCrMo-4 weldments offered better tensile properties compared to ERNiCr-3 weldments, whereas the impact toughness was found to be better for ERNiCr-3 weldments. Line mapping analysis was carried out to study the elemental migration across the weldments. The structure-property relationships of the weldments were arrived at using the combined techniques of optical and scanning electron microscopy. Optical and SEM/EDAX analysis showed that there is no prominent occurrence of deleterious phases at the weld zone on employing these filler metals.

Key words: Inconel 718, Pulsed current gas tungsten arc welding, Mechanical property, Deleterious phase

K. Devendranath Ramkumar, R. Jagat Sai, G. Sridhar, V. Santhosh Reddy, P. Prabaharan, N. Arivazhagan, N. Sivashanmugham. Influence of Filler Metals in the Control of Deleterious Phases During the Multi-pass Welding of Inconel 718 Plates[J]. Acta Metallurgica Sinica (English Letters), 2015, 28(2): 196-207.

Figures/Tables 14

Table 1 Chemical compositions of the base and filler metals (wt%)

Metal	C	Si	Mn	Cr	Ni	Nb	Mo	Fe	Others
Inconel 718	0.026	0.102	0.085	17.49	Bal.	5.03	2.96	20.3	P 0.009; Cu 0.025; Al 0.572; Ti 0.905; Ta < 0.02; N < 0.005; Co 0.102
ERNiCr-3	0.02	0.1	3.1	20.5	Bal.	2.6	-	1.0	P 0.002; Ti 0.5; S 0.09; Cu -0.5
ERNiCrMo-4	0.02	0.08	1.0	15.5	Bal.	-	16.0	4.5	P 0.04; S 0.03; Cu 0.25; Co 1.1; W 3.5

Table 2 Process parameters employed for PCGTA welding of Inconel 718

Filler	Number of pass	Voltage (V)	Current (A)		Pulse frequency (Hz)	Shielding gas flow rate (L/min)	Filler wire diameter (mm)
Filler	Number of pass	Voltage (V)	Background current	Peak current	Pulse frequency (Hz)	Shielding gas flow rate (L/min)
ERNiCrMo-4	4	12.8-16.1	160	213	7.5	15	2.4
ERNiCr-3	4	11.6-14.5	160	213	7.5	15	2.4

Fig. 1 a Photographs and the macrostructures of the PCGTA welded Inconel 718 plates employing ERNiCr-3 and ERNiCrMo-4 fillers: a, c ERNiCr-3 filler; b, d ERNiCrMo-4 filler

Fig. 2 Microstructures SEM images showing the microstructures of PCGTA weldments emplying ERNiCr-3 a, c, e; ERNiCrMo-4 b, d, f fillers: a, b composite zone; c, d weld zone; e, f HAZ

Fig. 3 Line mapping analysis on the as-welded PCGTA weldments of Inconel 718 employing ERNiCr-3 filler

Fig. 4 SEM images and EDS analysis results on HAZ a, b and weld zones c, d of the Inconel 718 weldments employing ERNiCr-3 filler

Fig. 5 Line mapping analysis on the as-welded PCGTA weldments of Inconel 718 employing ERNiCrMo-4 filler

Fig. 6 SEM images and EDS analysis results on HAZ a, b; weld zones c, d of the Inconel 718 weldments employing ERNiCrMo-4 filler

Fig. 7 Vicker’s micro-hardness curves of the PCGTA welded Inconel 718 samples employing ERNiCr-3 a; ERNiCrMo-4 b fillers, comparison chart of hardness of the weldments c

Table 3 Hardness values of different positions of the Inconel 718 weldments

Filler	Description	Cap	Filler	Root
ERNiCr-3	Average hardness of the weldment	214.7	219.7	227.0
	Average hardness at the weld zone	211.7	229.5	236.4
	Peak hardness at the weld zone	230.2	249.9	281.2
ERNiCrMo-4	Average hardness of the weldment	230.4	229.5	231.4
	Average hardness at the weld zone	237.3	238.6	238.0
	Peak hardness at the weld zone	282.6	265.9	267.8

Table 4 Tensile properties of the Inconel 718 Weldments with different fillers

Property	ERNiCr-3			ERNiCrMo-4
Property	Trial 1	Trial 2	Average	Trial 1	Trial 2	Average
Maximum load (kN)	19.8	20.5	20.2	21.1	21.2	21.2
Maximum tensile strength (MPa)	677	700	688.5	726	724	725
Young’s modulus (GPa)	59.8	57.1	58.5	53.2	50.3	51.8
Tensile strain at break (%)	64.5	68.1	66.3	78.1	76.1	77.1
Fracture zone	Weld region			Parent metal of Inconel 718

Fig. 8 Fractured tensile samples and SEM fractographs of Inconel 718 weldments employing ERNiCr-3 a, b; ERNiCrMo-4 c, d fillers

Table 5 Impact properties of the Inconel 718 weldments with different fillers

Property	ERNiCr-3			ERNiCrMo-4
Property	Trial 1	Trial 2	Average	Trial 1	Trial 2	Average
Impact energy (J)	70	56	63	48	54	51
Fracture mode	Ductile			Ductile

Fig. 9 Impact test samples and corresponding SEM fractographs of Inconel 718 weldments employing ERNiCr-3 a, c; ERNiCrMo-4 b, d fillers

References 25

[1]	J. Gordine, Some Problems in Welding Inconel 718, paper present in AWS Spring Meeting, San Francisco, California, 1971
[2]	W.D. Cao, R. Kennedy, Superalloys 2004 (TMS, Warrendale, 2004), pp. 91-99
[3]	R.G. Thompson, B. Radhakrishnan, D.E. Mayo, in Superalloy 718—Metallurgy and Applications, ed. by E.A. Loria(TMS, Warrendale, 1989), pp. 437-455
[4]	M. Qian, J.C. Lippold,Acta Mater. 51, 3351(2003)
[5]	M. Prager, C.S. Shira, Welding of Precipitation Hardening Nickel Based Alloys (Welding Research Council, Bulletin No. 128, New York, 1968)
[6]	G.D. Janaki Ram, A. Venugopal Reddy, K. Prasad Rao, G. Madhusudhan Reddy, Sci. Technol. Weld. Join. 9, 390(2004)
[7]	S.G.K. Manikandan, D. Sivakumar, K. Prasad Rao, M. Kamaraj, Mater. Sci. Forum 710, 614 (2012)
[8]	W.J. Mills,Weld. Res. Suppl. 76, 113(1987)
[9]	C.H. Radhakrishna, K. Prasad, Rao. J. Mater. Sci. 32, 1977 (1997)
[10]	R.G. Thompson, D.C. Mayo, B. Radhakrishnan, Metall. Trans. A 22, 557 (1991)
[11]	R.G. Thompson, D.C. Mayo, B. Radhakrishnan, Metall. Trans. A 22, 887 (1991)
[12]	L. Nastac, D. Stefanescu,Metall. Mater. Trans. 27, 4075(1996)
[13]	M.J. Cieslak, T.J. Headley, G.A. Knorovsky, A.D. Romig, T. Kollie, Metall. Trans. A 21, 479 (1990)
[14]	J.W. Prybylowski, R.G. Ballinger, Corrosion 43, 111 (1987)
[15]	R.G. Carlson, J.F.Radavich, in Superalloy 718—Metallurgy and Applications, ed. by E.A. Loria(TMS, Warrendale, 1989), pp. 79-95
[16]	W. Zhang, L. Liu, T. Huaung, Z. Yu, F. Fu,Rare Met. 28, 633(2009)
[17]	W. Zhang, L. Liu,Rare Met. 31, 541(2012)
[18]	G.D. Janaki Ram, A. Venugopal Reddy, K. Prasad Rao, G. Madhusudhan Reddy, J. Mater. Sci. 40, 1497(2005)
[19]	G.D. Janaki Ram, A. Venugopal Reddy, K. Prasad Rao, G. Madhusudhan Reddy, J.K.S. Sundar, J. Mater. Process. Technol. 167, 73(2005)
[20]	G.D. Janaki Ram, A. Venugopal Reddy, K. Prasad Rao, G. Madhusudhan Reddy, Pract. Metallogr. 42(10), 481(2005)
[21]	G.D. Janaki Ram, A. Venugopal Reddy, K. Prasad Rao, G. Madhusudhan Reddy, Mater. Sci. Technol. 21, 1132(2005)
[22]	G.D. Janaki Ram, A. Venugopal Reddy, K. Prasad Rao, G. Madhusudhan Reddy, Mater. High Temp. 23, 29(2006)
[23]	G.D. Janaki Ram, A. Venugopal Reddy, K. Prasad Rao, G. Madhusudhan Reddy, Trans. Indian Inst. Met. 59, 87(2006)
[24]	J.N. DuPont, J.C. Lippold, S.D. Kiser, Welding Metallurgy and Weldability of Nickel-Base Alloys (Wiley, New Jersey, 2009)
[25]	J.R. Davis, Tensile Testing, 2nd edn. (ASM International, Ohio, 2004)