But... isn't the melting point of the alloy far above the melting point of the constituent pure metals?

I'd ask my metalurgist friend, but I don't want to look like an idiot.

In a common example, the alloy of iron and carbon known as cast iron melts at a lower temperature than pure iron or pure carbon (or low-carbon steel).

But there are other cases where an alloy has higher melting point. Ti(88)Al(12), for example.

Film cooling and coatings are what allow operating temperatures above the melting temperature. That doesn’t mean the metal is above its melting temperature.