olddog,
Brittleness is HIGHLY dependent on alloy selection. All stainless is NOT the same, just as all steel is not the same. Razor blades are made from 1080 and you can snap them with your fingers (be careful!). Most shims are made from 1010 and you can bend them in 1/2--several times, even.
What alloy did you use on the gear pump? I would bet had it been made from 17-4 and nitrided for wear resistance the gear would have outlive both you and I combined. One of the BIG reasons to use precipitation hardening steels is because they aren't subjected to the violent quench of the heat treating process. The quench sets up tremendous internal stresses and many times causes cracking. Your heat treater has to be GOOD and know what they are doing. Choosing heat treaters is much like choosing a wife...better get it right the first time or it's going to cost you a lot of $$$.
David
