Protective finish for Maraging Steel

[gfbotha]

Hallo

We currently use a steam induced spinelling (SHS) process to provide a critical, highly stressed maraging steel welded assembly, with limited corrosion protection and also a nice black surface finish. Most, but not all, of the surfaces get painted after all manufacturing processes are completed. Removing loose oxide from certain areas to be used for subsequent bonding, pose a constant problem.

Keeping hydrogen embrittlement, etc. in mind; is there any other process somebody is actually using with good success for this type of application? Thanks.

Regards

 

[israelkk]

This is exactly what was used in the company I worked for. What I can add is that to completely dry the parts we dipped the parts in a water repelling oil after the steam spinelling to repel any trapped water that may create corrosion.

 

[WKTaylor]

What steel alloy(s)? What welding spec/process? What heat treatment/spec? Shot peened? What environmental extremes?

Regards, Wil Taylor

 

[gfbotha]

Sorry for my late response, WkTaylor - was out of office.

Maraging steel gr. 250, aged for 6 hours @ 480°C.
Laser welding with filler material (butt & fillet).
Not shot peened (only "sand blasted").
Exposed to elements/rain and elevated temperature (80° for 30min, 120°C for 30s) during several flight sorties.

Meanwhile the question came up whether there could be a problem with our steam process parameters, possibly yielding the wrong combination of oxides (magnetite Fe3O4 vs Fe2O3)... Our steam enters at 3bar.

Thanks