PWHT after hard facing

[chok7]

Query around effect of PWHT on hard facing weld overlays. For context, have some standard carbon steel piping where PWHT is completed after hard facing (typically HF is done after PWHT, but due to geometry these ones have to be HF first, built in segments and then whole thing PWHT).

Hard facing is a chromium carbide weld overlay to AS2576/2560-B7, and PWHT is at 600 deg C for 30 min hold time with 100deg/hr max heat up / cool down rate.

Has anyone got any info or experiences around chromium carbide overlays softening, microstructure changes, cracking further, etc. after PWHT?

 

[dtimberlake]

I bet the overlay OEM will have something to say.
I think some weld overlay materials are meant to be used in the as-welded condition.

 

[EdStainless]

Some will and some won't.
Ask for data and if they don't have it you will need to generate it.
You may need to play with the preheat temp for the overlay in order to control the results.

 

[DVWE]

You’re going to have to give us the whole picture here. Why are you PWHT carbon steel pipe, and then hard facing? What is driving the PWHT requirement?

 

[Dhurjati Sen]

You need to carry out localised PWHT of the CS after duly protecting the hard facing.
You would not get data on this as this is not a standard practice.
The contractor/ vendor needs to take a deviation from the client before going ahead with this.
The client may agree based on difficulty of carrying out the job and urgency in getting the project completed.