You mean, certainly, which ceramic has a maximum thermal shock resistance? For a quick heating and cooling in a vacuum oven just such ceramics are necessary.

These are ceramics either with very low thermal expansion coefficients or with a very high thermal conductivity.

BeO and AlN ceramics are good resistant to thermal shock because they have very high thermal conductivities (for BeO: 250-325 W/mK; for AlN: 180-220 W/mK). In addition, AlN also has a low thermal expansion coefficient of 4.63x10-6 K-1.

There is a much more popular and much cheaper material for vacuum furnace: graphite. Graphite is extremely thermoschok resistant, because it has a high thermal conductivity (119-165 W/mK) as well as a very low thermal expansion coefficient ( approximately 2x10-6 K-1).

Even a cheap material such as quartz glass is perfect suitable for applications with thermal shock. Its thermal expansion coefficient is extremely low: approximately 0,5x10-6 K-1.

Thank you for the information.

I am looking for something that can be cast in a mold with metal pieces in it that became hard without going over metal parts melting point.

There are some porcelains used by dentists but I do not know about thermal conductivity and expansion coefficients

Graphite is an interesting material that not fuses but sublimates