Thanks for the file, TAK.
Lots of stuff inside and some combinations I have never used, like Specular metal with over 900% and MIX with Specular plastic. Just to name something I just would not even think to set up in that way, so no experience with such. In combination with 300% Bump, not done in 18 years. So, there is only one way: Support. I don’t want to explore that even deeper, it feels like anything lower in value/parameters is not to your liking. Support.
What I would do is pretty simple, you did already the preparation for that. Thanks :o) Setting up the projection in the extra Bump material is the key here. I would just do what a welding would really look like, a change in surface. (After all, bump is just an fake, and doesn’t change the silhouette at all!)
So, I took your welding “texture” and placed the “Gradient” over it in an Layer channel. Can be done anywhere for the time being. So the outside of the texture is black.
Then I go into the Displacement channel, and use the “Projector” I open this material-channel in an extra editor and lock it. (right upper corner of the editor) I copy the channel that has the “Layer Shader” and go to the Projector in the open Editor. I paste it into the Texture, via fly out menu, the little triangle left sided from the Texture field. Then I select the Texture Tag from the “alfa based material (again Texture tag—not the Material Tag!), and go back to the Projector and click the button “Paste Tag”. The tile is off! The Displacement needs to be set to all the values as in the example, especially the intensity from center to just intensity.
You can see in the example scene that I have worked with one material only, which I would prefer, to keep it simple.
With the displacement now changing the geometry, the previous Alfa material can now Mix some color over this, just the Color channel, all black for no color.
All the best
Sassi