STUDY OF INCONEL 718 ALLOY TESTED BY HEAT-CYCLING

This paper investigated Inconel 718 (UNS N07718) alloy after some heat-cycling tests. The study continues prior tests realized in INR Pitesti concerning utilization of some nickel-based alloys in the heat-exchangers and steam-generators construction of future Nuclear Plants. Technical parameters of thermal cycling: 50 & 200 cycles, 25 C°/minute heating-cooling rate, 450-1000°C temperature range. The analysis consisted in metallographic examination (microstructure), Vickers microhardness (MHV0.1) and traction tests. The samples were investigated by Olympus GX 71 optical microscope, OPL tester in automatic cycle and Walter Bai traction machine. The average grain size (G) was determined by linear interception method (ASTM E-112). The micro hardness was calculated by the relationship of the device technical book. The Strength-Deformation diagrams furnish data of mechanical properties: tensile strength (Rm) and elongation (A). The tested alloy was compared with the "as received" material, and the results showed a good metallographic and mechanical behaviour of the alloy after these thermal-cycling tests.