Custom Knife Failure

Well that didn't go as I'd planned. I was working at the outer edges of the envelope and I went too far. During the quenching process the edge of the blade cracked, rather uniformly down the edge. Given that the crack spacing follows the initial curvature it appears that the cracks were formed in tension in the martensitic portion of the blade. This is not particularly surprising as martensite has a different volume due to the phase change. I had clayed the blade and left the edge exposed to only transform it while keeping the spine of the knife more ductile. This resulted in a overly large curvature and the subsequent cracks. You can see the cracks in the photo.

Back to the forge, and I'll try again. The interesting thing about this was that it reminds me of some past work. The crack nucleation follows the same sort of nucleation I induced in an expanding ring study I did many years ago. In that case the number of cracks and subsequent fragments could be varied by heat treatment of a steel ring which was then explosively loaded to expand and fracture it.

As with life every failure can be valuable as long as you learn from it. This time around I'll start with a straight blade and keep the variable heat treat and quench.