https://www.abana.org/downloads/controlled_hand_forging/CHF_2.pdf

see this link

best regard

Appreciate your contribution but HPT stands for High Pressure Torsion and I am looking for proper material to make anvils which can take up to 20GP.

WC bar may work. in case of high pressure FSP it works well.

Best regards,

Thanks, I already have tried WC bars from Guhring;  the maximum strength is ~4GP even for the best grade (according to their spc sheet). In the case of friction stir processing, the maximum pressure is typically bellow 1GPa

Diamonds have been used for large GP's causing phase transformation, but their foot print is too small

Ceramic?

thanks for your suggestion, any particular ceramic or perhaps a commercial name?

Could be alumina. The hardest and the cheapest.