Abstract
The proposed Generation IV nuclear energy systems are aimed at making revolutionary improvements in economics, safety and reliability and sustainability. Because the materials will be used under high pressure and temperatures, the requirements for cladding materials are: good mechanical properties, corrosion resistance, resistance to neutron irradiation, low susceptibility to stress corrosion cracking and micro structural stability. Of the candidate alloy systems that could be considered for high temperature applications, nickel-based alloys were selected as promising material based on experimental results. This paper shows the changes of grain size nickel based alloys suck as: Incoloy 800HT, Inconel 617, 230 and 718 that appear after a thermal treatment like thermal cycling. One sample of each alloy was meekly at a thermal cycling of 25 cycles. The parameters which were choose for this treatment was: the maxim temperature of a cycle 700°C and the minim temperature of a cycle 400°C. In the as received Incoloy 800 HT has the biggest grain size, fallowed by Inconel 230 and Inconel 617. Inconel 718 has the smaller grain size, even 4 time smaller then Incoloy 800HT and 3 times smaller then Inconel 230. It could be observe a big decrease of the grain sizes of all the alloys after the thermal cycling treatment of 25 cycles. For the first tree alloys Incoloy 800HT, Inconel 617 and Inconel 230 it’s detected a decrease ten time higher compared to the values of the grain size of the alloys on the as received. For Inconel 718 appear a smaller decrease of the grain size after thermal treatment compared with the as received appear. During the thermal cycling process, materials are alternately cooled and (sometimes) heated until they experience molecular reorganization. That’s way after the thermal cycling of 25 cycles it could be observed that the hardness of the alloys increase and the grain sizes decreased. This reorganization "tightens" or optimizes the particulate structure of the material throughout, relieving stresses and making the metal denser and more uniform (thereby minimizing flaws or imperfections).
Keywords: Nickel Alloy, Incoloy 800HT, Inconel 617, Inconel 230, Inconel 718