Look for ASTM B408, ASME SB-408 or UNS N08800. The Young's modulus and S Stress values are published with suitable numbers to about 1100 degree F in Various ASME B31.1, B31.3, "Physical and Mechanical Properties". The ASME Boiler and Pressure Vessel Code, Section II Materials, Part D - Properties - S values avalance down from 13000 psi at 1100 deg F to 2000 psi at 1300 deg F. Thus, I would avoid N08800 above 1100 degree F.
John