Hi, i am new here. I got a question.

For the base material, i am using 4130 steel.
For coating, i am using colmonoy 5.
Due to its size L 250 x D 130, the fusing does not look good.
Do i have to do annealing on the steel first before starting to spray?
If not then is there any other way?

Thanks

Dear yapwx,
Its a very tricky job to do spray fuse on the bigger diameters. You have to balance heat input on the job.U may have to practice a lot to perfect this technique.
Best of luck
Vijay Deshpande

Dear Yapwx
Like Vijay says, it is a careful balance of heat input and overheating. 250 x 130 Diameter is not excessive, but I would personally use 3 fusing torches, two for heating, and one for fusing. There are so many little tricks of the trade is spray fuse it would be nearly impossible to cover here, but practice first on sample pieces, repeatedly. Slow cooling in Vermeculite would be good.

Alternative process, Plasma Welding

Thanks for all your help, i will try with more test pieces to see which way is the best. Thanks again.

Hi Yapwx

to the Surface Engineering Forum.

Fusing is a bit of an art. Much practice and gaining experience needed. Good luck

I have tried a few test pieces, and all of them have porosity. The best is the one i keep at a slightly higher temperature and longer fusing time. But it still has porosity. And with heat threatment, it will get worse. Is there anyway you all can think of to get no porosity?

Thanks for all your help, in advance.

Other than improving your fusing procedure and skills, you could try plasma or HVOF spraying of the coating. The coatings are denser and cleaner than normal flamespray and fuse much easier and give better results.