Experience with nickel overlay on stainless steel

[BWmatleng]

Has anyone ever used a nickel alloy on a stainless steel base tube? I am being told by the business folks in my company that "all the utilities" are asking for TP304H tubing with 622 overlay. The reason it is being requested is that the 622 offers erosion protection for the sections, specifically around soot blowers.

I am concerned about fabricating this combination, how the different cladding processes will impact the ductility, and how long this combo will last in service with the difference in thermal expansion. Any thoughts?

 

[metengr]

I have seen the use of 622 weld overlay on reheater and superheater tubes. I doubt all of the utilities are clamoring to use this combination, we have not in the past.

I would consider shields versus overlay for sootblower erosion. Can the overlay be done, yes. However, the 622 was designed to offer increased corrosion resistance in waterwall tube sections (sulfur fireside corrosion) and is not going to buy that much in erosion resistance.

 

[weldstan]

None of our Power clients have as yet specified 622 overlays on 304H or 347H tubes. Have done so on waterwall tubes for corrosion protection as per metengr.
622 overlays on stainless steel have been done many times for corrosion protection so it could readily be done on 304

As metengr states, 622 weld overlay has been used on waterwall tubes many times. None of our Power clients have as yet asked us to weld overlay 304H or 347H tubes.
622 weld overlays on stainless steel have been made in numerous applications for corrosion protection in the past. I foresee little problem with 622 [link undefined]Link[/url]overlay of tubes in your proposed application.






















h

 

[BWmatleng]

I appreciate the quick responses! You both confirmed my thought that 622 wouldn't help in erosion since it is designed for corrosion protection.

My company is currently having trouble bending tubes of this combination TP304H with 622 cladding. Since bends with 622 have been successfully made in the past (although with a different base metal), I have been investigating what is different now. The 2 major differences seem to be the base metal and the overlay process. The purchasing department switched overlay vendors and went to a shop using laser cladding (still don't know if it was hot wire or powder) instead of our usual overlay vendor that performs a TIG wash.

Any thoughts on the impact of a laser process vs. traditional welding being a part of the ductility problem? The dilution seems to be high based upon preliminary PMI results of the overlay.

 

[metengr]

BWmatleng;
First, are the cracks circumferential in orientation and confined to the overlay deposit or are they propagating into the 304H tube material? The 622 in of itself should be very ductile and easily take forming strains.

Have you done a met analysis using your lab at B&W? I know several of the materials folks remaining in Barberton.