That big block of metal is inconel, an extremely tough "austenitic nickel-chromium-based superalloy," one of the strongest metals known to humans, used in "in extreme environments subjected to pressure and heat" like nuclear plants. How do you cut such a hard thing? Let's watch a video.
That's a ceramic head rotating at very high speed. There are other ways—like water cutters—but only ceramic cutters can machine inconel at high speed.
When heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack. Inconel retains strength over a wide temperature range, attractive for high temperature applications where aluminum and steel would succumb to creep as a result of thermally-induced crystal vacancies..