Recommendation? Weird streaks on W-2 blade - carbide separation?

[Dmitry5]

W2 blade with hamon. Ground after heat treat. 1475 F, 10-15 min, Parks 50.
What are these light, hard (?) steaks I see? I did the same blade in the same batch with a thinner, pre-ground blade and do not see them. This is sanded to 1500-2000 so not finishing artifact. Carbide separation? Why cant I see it on the other blade from the same steel and finish?
Any ideas?
Thank you!

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[Joshua Fisher]

Did you alternate sanding direction while hand sanding through the grits? So you are saying this blade was full thickness before quenching? What were your grinding steps?

 

[Dmitry5]

Did you alternate sanding direction while hand sanding through the grits? So you are saying this blade was full thickness before quenching? What were your grinding steps?

Yes alternated directions, this came out after etch so I do not think its related to sanding. The bevels were not ground prior to heat treating if I recall correctly. Grinding with 36, 80, 120, 220 structured, then hand send.

 

[Keith Nix]

Looks like hamon

 

[Stacy E. Apelt - Bladesmith]

Those could be several things.

One is blade surface contamination caused in the grinding. Metal from the belt gets pressed and literally welded to the blade surface. This happens with stainless and carbon steels when a blade of one of those metals is ground prior to the other type. You can try re-sanding with brand new 120 and 220 belts and lighter pressure. If it goes away, the culprit was contamination of one of the original belts.

Another possibility is alloy banding caused by the carbides or alloys separating in the HT.

Another is that the metal had the alloy banding from the factory.