All About Pocket Knives

I've had this old cast iron looking hatchet for a while now......been listed on ebay with not takers.
I decided to use it the other night. I took a few wacks to make some kindling and the edge began chipping off...
I was using wood, not concrete as my base.

I made maybe a dozen wacks and this.....

Scott, I notice in the enlarged view of the first photo, there appears to be rust all along the big chips. Within the chips. So I would conclude that rust had developed below the surface. Granted that is a guess. But perhaps someone will come along who has some real knowledge of metallurgy.

low quality cast head. cast metal is always more brittle no matter the composition.

I had something like that happen years ago, I borrowed a double bit are from my grandad to use cutting some small fir trees we were falling for fire wood.
I used the axe to chop off some dry limbs about the diameter of a pencil. I had chips about the size of the diameter of a pencil out of the edges.

I bought my grandad a new axe and kept his old one.
I filed the chips out of the edges (both sides chipped) and have used that axe for the last 40 years with never another chip.
I don't know if somehow the edges had work-hardened or just what had happened, but it has never chipped again.