MagnaMagicBtu

So I got some precups out of this 7.3 IDI diesel engine I'm rebuilding. These cups to my knowledge are made out of Inconel, a very,very hard abrassion resistant and corrsion resistant alloy. They are hard as hell but also very brittle. I don't understand why they used a brittle metal for a high heat and high pressure application, I think a softer metal like mild-steel would do better as it will expand slightly rather than cracking. It also is left unharmed by hydrochloric acid and Lye. So the question is: Why a very hard brittle metal rather than than a softer metal in a high pressure situation? I think even Titanium would perform better than Inconel as it will not crack when subjected to high stress. They go into this Indirect Injected diesel engine, where air is forced into a pre-chamber (precup) and fuel is injected into the precup and the explosion uses up all the o2 in the precup so it travels down into the main chamber where the rest of the o2 is via the angled passage of the precup. Here are some nice pictures to see what a "Precup" is. They are also very expensive, costing $70-100 a piece. So the question is: Why a very hard brittle metal than a softer metal in a high pressure situation? would expanding slightly be better than cracking?