3. Experimental Methods

Reference: [1] J. W. Elmer and D. D. Kautz, “Fundamentals of Friction Welding,” in ASMHandbook, Vol. 6, Welding, Brazing, and Soldering, Materials Park, OH: ASM International,1993, pp. 150–155.

Friction and Fusion Dissimilar Welding of Stainless Steel to 1018 Steel

Nathan Switzner1, Zhenzhen Yu1, Michael Eff2, Arthur Fonseca1, Stephen Liu1

1. Colorado School of Mines, 1500 Illinois St., Golden, CO 804012. EWI, 1250 Arthur E. Adams Dr., Columbus, OH 43221

2. Objectives Compare properties of welds made by friction and fusionprocesses with the down-selected parameters. Evaluate the heat affected zone (HAZ) microstructure andits impact on mechanical properties.

Friction welds had a narrower HAZ in the1018 than the fusion weld as observed in thehardness map.

Friction welds had fine Widmanstatten ferriteand 2nd phase in the 1018 steel near the bondline.

Fusion welds had fine equiaxed ferrite and2nd phase near the bond line due to the multi-pass process.

5. Discussion

Acknowledgements:The American Welding Society (AWS) isgratefully acknowledged for fellowshipsupport of this research. Dr. T. Lienert fromLANL is thanked for his technical support, Dr.J. Gould, T. Stottler and EWI for frictionwelding, D. Chirichello and Exova Lab forhardness testing, and the CSM Welding Centerstudents and faculty.

1. Problem StatementAs a solid-state process, friction welding avoids solidification and segregationproblems which are typically associated with fusion welding of dissimilar metals. [1] It is essential to identify microstructure-property relationships to compare frictionand fusion welding.

Friction welds:• 304L stainless steel and 1018 steel bars of25 mm diameter & 100 mm length.

• Equipment: MTI 120 Inertia Welder Fusion weld:

• Multi-pass bead-on-plate flux cored arcweld to deposit 309L on 25 mm thick 1018steel plate (welded on end grain forcomparison with friction weld).

• Equipment: Miller Axcess 450 in DCEN,heat input of 1.3 kJ/mm for high deposition.

Digital image correlation (DIC) method wasused to monitor strain during tensile testing.

Hardness mapping was performed using aStruers Durascan Automatic Tester.

4. ResultsMicrostructure

304L stainless bar

flash

partially deformed

zone

deformed zone

fine Widman-statten ferrite & 2nd phase

intercritical austenite

transformed to ferrite & 2nd phase

Fusion Weld

309L

Tensile Tests

interface

reheated fine grain HAZ

intercritical HAZ

intercritical austenite

transformed to ferrite & 2nd phase

ferrite & pearlitede-carburized zone, then fine

ferrite & 2nd

phase in 1018

Vic

kers

Har

dnes

s

304L Stainless

1018 Steel

StrainBond LineFracture

in 1018

1018 steel bar (2% nital etch)

subcritical HAZ

309L weld deposit (Kallings #2 etch)

1018 steel plate

5 mmfusion line HAZ

bond lineHAZ

Microhardness

5 mm

304L 10181018

For all dissimilar welds, necking andfinal fracture was in the 1018 steel.

304L bar

R 6 mm

10 m

m

x2 6 mm

3 mm

bond line

1018 bar

25 m

m g

age

leng

th

flash

2 mmtensile bars

metallographic sample5 mm

6. Conclusions Friction welds had higher tensile strength

than fusion welds. Tensile fracture occurred in the soft HAZ of

the 1018 for both dissimilar welds. The fusion weld resulted in a de-carburized

zone in the 1018, not found in friction welds.

5 mm 5 mm

1018 1018

309L

ferrite & pearlite

1018base metal

Friction Weld

Digital image correlation (DIC) example for friction weld tensile test

tensile bars

Fusion Weld Approx. 5 mm wide

soft zone in 1018

Friction Weld Approx. 2.5 mm wide soft zone in 1018 Work-hardening in 304L near interface

309L