Another voice heard from, as a mechanical engineer, I know a bit about metals.
First it looks like there are two separate places where the knife edge chipped, perhaps the user might have stopped chopping after it chipped the first time.

A knife is made for cutting, an axe for chopping, two distinct operations which require different edge geometries, heat treats and hardness. To use one for the purpose it is not designed for will give less than optimum results.

My two cents

Peter