All right, a new thing, we shall see if it works and is popular. I am going to try blogging.
Today, re-learning old lessons about part failure as it relates to knives and heat treating, and in this specific instance, corrosion, mainly. Below you will find two pictures of a broken 52100 filet knife which snapped under extreme stress being flexed further than I should have, just to see. In the picture of the broken cross section, the lower pic, you can see that there is a black spot on one flat side of the blade bevel. That black spot is the origin of the crack propagation, and was caused by deep corrosion from the blade forging being repeatedly wet and dry, and never having been properly cleaned of high temperature salt from annealing. I found it whilst cleaning recently, and knew the deep pits were there, but thought I would give it a go anyway. This is what happened. You can see that the grain in the fracture is nice and fine, but even with spot on heat treating and high quality materials, surface defects with depth can cause failure under stress.
