Help/Advice with "pitting"

[Misfire]

Quick background:

I've been making knives recreationally for about a year and a half. Until recently I've only used stainless steel with the majority being finished with a media blast. What I've been doing is wet sanding the bevels down to 400 grit and then sending it off for heat treat. When I get them back I wet sand it again with 400 grit (moderately) to get any residual scale off and then I media blast it. I have never had a problem getting a nice, even media blasted finish with stainless steel.


Recently I started making knives out of O1. I've been using the same method for O1 as I have with stainless. Hand sand the bevels and flats to 400 grit and then send them off to heat treat. The difference is that when I get the O1 back the finish is no longer even and requires a HECK of a lot of hand sanding to get the finish back to where it was prior to sending it off.

The oil quenched steel appears to have A LOT of little pits and imperfections once it comes back from heat treat. So.. I'm a noob and know nothing beyond the theory of heat treat.

From what I remember the heat treater told me that he does a couple cycles of normalizing and two or three heat treat cycles.

Is this common?

Am I doing something wrong prior to sending them off that is causing this "issue?"

Here is a pic of what I'm asking about. Prior to sending them off for heat treat the surface was flat, clean, even and (to my eye) without these pits, voids and imperfections.




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[Ed Tipton]

Misfire...After reading and re-reading your post, it reads as though you do not do any forge work or heating of the steel in your shop, so I'm guessing that the first time your blade sees any heat is at the heat treating facility.
Since I do all of my own forging, hardening, and tempering, I have full control over the entire process. In my shop, if I were to see this type of problem, I would know that my flame would have been slightly oxidizing...and perhaps a little too hot. Without being involved directly in the process, you are at the mercy of your HT facility. I have never sent a blade out for HT, but I would certainly expect a HT provider to be able to do a simple HT on an o1 knifeblade. If you have not already done so, I would take the blade to him and show him what it is doing. I f you have already done that, then perhaps you need another heat treater....or better yet...do it yourself.

[Doug Lester]

I'm with Ed on this, there is not reason that I see that there should be that amount of pitting on a blade. I don't work with O1 but I do forge and heat treat carbon steel blades and I have never seen pitting like that. A flame from a gas forge diredted down on the steel can cause bad pitting but I think that it would be seen in the stainless also if that's how the treater was heating the blades. If there is a blade that you can sacrifice you might break it and see what the grain looks like to see if he is overheating it during austinization.

I would also second Ed's opinion that you either need to send your blades out to another heat treater or learn to heat treat the O1 yourself.

Doug

[Misfire]

Thanks for the input and advice!

You are correct. I do not put any heat on any of my blades. I simply don't have the tools, knowledge or confidence to do so...yet.


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[WBE]

01 requires around a 20 minute soak at quench heat. It has to have decarb and scale protection to not pit. I don't think your heat treater knows how to work with 01.