Is this what stress fractures look like?

S

syvmn

Joined
Apr 5, 2009
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Messing around with my new forge I heat treated a piece of W2 in water. I normalized at 1500 and 1475 before quenching at 1425 into 115F water. Things seemed to have gone decently well when I noticed these hairline "scratches". Looks to me like faint cracking. They only show up on one side of the knife though so it makes me wonder what they are? Anyone have experience with this?

IMG_1045_zps08e5e921.jpg
 
Looks like it. One way to find cracks is sand the blade down pretty good then do an etch (decent strong one). If you dont see them right away then do a quick sanding and clean up the blade then let it sit around for a while. The etchant will leak out of the cracks and show up. Sometimes it will take a while.
 
I would still be leary even if you sand them out. I have sanded a blade that looked perfect. Couldnt see any cracks at all. Etched the hamon and finished sanding and polishing. Went to take some photos of the finished product about an hour or two later after the sanding. Taking the photo was when I noticed the etchant was causing the crack to show up from leaching out.

Kind of the same theory as dye penetrant testing which I am suprised more guys dont use. Guess its cost and not always really needed. I was thinking of it after that fiasco of handsanding all day just to end up tossing the blade.
 
I hear Busse uses penetrant after that issue with flaws in the S7 used in their Scrapyard line. Those look like either cracks or cold laps/fins from rolling/forging the bar/plate. The effect is the same for a knife, ie they really aught to be removed. We had some cold laps show up in some bridge girders years ago, but they weren't deep enough to require repair. They were 1/32" deep on girder webs nearly 3/4" thick in MUCH tougher steel than used in knives.
 
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