నైరూప్య

Thermodynamic calculations for knowing local very high temperatures in service in refractory nickel alloys

Patrice Berthod

Three alloys based on Ni-30wt.%Cr and containing carbides were cast and heated for several hours at targeted temperatures chosen between 12500C and 13400C. Fractions of carbides or molten areas were measured by image analysis. Comparison between measured carbides fractions and results of thermodynamic calculations were consistent for 1250 and 13000C. For the highest targeted temperatures mismatches were noticed. Thermodynamic calculations performed to reachmeasured values of carbide fraction allowed an accurate determination of the real temperature. Comparison between metallography and calculationswere never so good concerningmolten areas. Thermodynamic calculations are able for determining real temperatures for mushy states but several conditions need to be respected.