Microstructual and mechanical studies of the dissimilar tabular joints of Incoloy alloy 825 and AISI 316 stainless steel

Figures & data

Table 1. Chemical compositions of the base metal and filler materials (wt.%).

	Base metals		Filler metals
Elements	Incoloy 825	Stainless steel 316	Inconel 82	Stainless steel 308	Stainless steel 309	Stainless steel 316
Ni	39.4	2.6	67	10.3	13.4	11.8
Fe	23.6	0.024	2.7	–	–	–
Cr	22	12.5	20.9	21	24.6	18.8
Mo	3.15	1.7	–	–	–	–
Cu	2.54	–	0.43	–	–	–
Ti	1.13	–	0.69	–	–	–
C	0.037	17.3	0.08	0.02	0.016	0.012
Mn	0.76	0.34	3.1	–	–	–
S	0.02	0.01	0.014	0.022	0.024	0.03
Si	0.24	0.014	0.41	0.69	0.74	0.71
Al	0.16	–	–	–	–	–

Table 2. The GTAW welding parameters used in this study; the heat input was taken as 0.7 EI/V, where E is welding voltage, I is current and V is welding speed.

Filler metals	Pass	Current (A)	Voltage (V)	Welding speed (mm/s)	Heat input (kJ/mm)	Total heat input (kJ/mm)
Inconel 82	Root	180	14.2	1.43	1.25	4.98
	Hot	160	15.6	1.17	1.49
	Filling	140	16.8	1.44	1.14
	Cap	140	17.4	1.56	1.09
Stainless steel 308	Root	180	15.3	1.72	1.12	4.95
	Hot	160	16.1	1.36	1.33
	Filling	140	16.9	1.2	1.38
	Cap	140	17.2	1.50	1.12
Stainless steel 309	Root	180	14.8	1.33	1.40	4.92
	Hot	160	15.6	1.26	1.39
	Filling	140	16.5	1.67	0.97
	Cap	140	17	1.43	1.17
Stainless steel 316	Root	180	15	1.65	1.15	5.15
	Hot	160	15.7	1.48	1.19
	Filling	140	16.4	1.12	1.44
	Cap	140	17.5	1.24	1.38

Figure 1. The dissimilar welded Incoloy alloy 825 and stainless steel 316 tubes, prepared specimens for tensile, hardness and metallography tests.

Table 3. Tensile strength and fracture position of dissimilar welded joints with different filler metals.

Filler metal	Tensile strength of dissimilar joint (MPa)	Fracture position
Stainless steel 308	472	Weld metal
Stainless steel 309	566	Weld metal
Stainless steel 316	536	Weld metal
Inconel 82	429	Weld metal

Table 4. The average hardness of weld metal for dissimilar welded joints with different filler metals.

Filler metal	Average hardness of weld metal (HV)
Stainless steel 308	169
Stainless steel 309	192
Stainless steel 316	162
Inconel 82	150

Figure 2. Light optical micrograph of AISI 316 austenitic stainless steel base metal in two different magnifications: (a) 50 µm and (b) 20 µm.

Figure 3. Light optical micrograph of Incoloy 825 base metal in three different magnifications: (a) 200 µm, (b) 100 µm and (c) 50 µm.

Figure 4. Optical micrograph of HAZ microstructure of Incoloy 825 in two different magnifications: (a) 50 µm and (b) 20 µm.

Figure 5. Interface between the filler 82 weld metal and the Incoloy 825 base metal.

Figure 6. Optical micrograph of HAZ microstructure of AISI 316 stainless steel in two different magnifications: (a) 200 µm and (b) 100 µm.

Figure 7. Interfaces between the filler 82 weld metal and the AISI 316 base metal.

Figure 8. Interfaces between the filler 309 weld metal and the AISI 316 base metal (a) and between the filler 309 weld metal and the Incoloy 825 base metal (b).

Figure 9. Optical micrographs of filler 82 welding metal microstructure in two different magnifications: (a) 200 µm and (b) 50 µm.

Figure 10. The microstructure of 309 weld metal near the fusion line in two different magnifications: (a) 100 µm and (b) 50 µm.

Figure 11. The microstructure of 309 weld metal centre in two different magnifications: (a) 100 µm and (b) 50 µm.