We want to friction weld P91 tubes to a WAAM printed nickel alloy tubes.
The deformation of the WAAM tube is much larger than that of the P91 tubes. This results in an expansion of the WAAM tube (see attachment).
The WAAM tube has always the tendency to expand in the radial outward direction, creating an unsymmetrical appearance of the weld.
One the one hand, the flash formation at the WAAM side is very small (you can only see a very small weld flash), but on the other hand, the deformation of the tube is large.
I suppose this has to do with the large ductility of the WAAM material ?
The parameters that I used for welding this :
- pfr = 100 MPa
- pforge = 200 MPa
- I used a first stage friction pressure of about 10 or 15 MPa
- rotation speed : 1200 rpm
- Allowed shortening during the friction phase : 7 mm
- Welding time : +- 20 sec
Can you give some advice how to improve the quality ?
Which welding parameters can be used to improve the results ?
Thanks and regards,
Koen
Material data :
- OD : 44.5 mm
- Wall thickness : 5.5 mm
P91 (based on the standard) :
- Rm < 585 MPa
- Rp0.2 = 415 MPa
- Elongation after fracture A% = 20%
- https://4.imimg.com/data4/BI/KK/MY-4947466/p91-alloy-steel-plate.pdf
WAAM Nickel alloy A82 (based on tests at BWI) :
- Rm = 542 MPa
- Elongation after fracture A% = 64%
You are write that flash formation is due to the large ductility of the WAAM material. To my opinion, some improvement of quality may be obtained by cooling of WAAM tube near welding zone.
The prelimenary profiling of the WAAM tube edge end is seemed another way to improvement.
Dear Serge V. Shil’ko ,
In a first step, I decreased all parameters : the welding time, the friction and forge force and the rotation speed. This had led to a better result, altough some expansion of the WAAM tube was still present.
You are right, providing a weld preparation might help.
Regards,
Koen
Dear Koen,
it will interesting to compare the flash formation during friction welding of another materials of tribopair having low and high ductility in the same regime of this technological process.
All the best,
Serge
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