Influence of microdefect on fatigue properties in weld fine grain heat affected zone on nickel molybdenum alloy steelSmaili, Fidan (Avtor) Vuherer, Tomaž (Mentor) weld jointFine Grain Heat Affected Zonemechanical propertiesfatigue crack growthThis research presents two possibilities to prepare and test the Fine Grain of a Heat Affected Zone, which, practically, could be considered as the weakest part of welded joints in the presence of any microdefect. It is a narrow zone located between the fusion zone and the unaffected base material; therefore, only a few methods are suitable to test its mechanical properties. The 18CrNiMo7-6 steel was used as the base material. As this steel is usually used for the production of dynamically loaded components, testing of its fatigue behaviour and fracture toughness was crucial, but also measurement of its hardness and impact toughness. To investigate the mechanical properties of a Fine-Grain Heat-Affected Zone (FG HAZ), two different methods for simulation of as-welded microstructures were used in this research: A weld thermal cycle simulator (WTCS) and austenitising in a laboratory furnace +[F. Smaili]20232023-03-31 16:32:44Doktorsko delo/naloga84040sl