Experimental Study On Environmental Mechanical Properties Of Micropillar Of Nickel-base Single Crystal Superalloy

Nickel-base single crystal superalloy has been widely used for aerospace engines and gas turbines for its excellent mechanical properties,and people pay much attention to it due to the serious problems come from its harsh service environment such as hydrogen embrittlement and thermal corrosion.Knowing the mechanism of hydrogen embrittlement and thermal corrosion enables people to make breakthroughs in the development of new materials.In this paper,the micropillar compression experiments were carried out on nickel-base single crystal superalloy which contains three different grain orientations with the help of micro experiment techniques(such as FIB machining,nano-indentation,etc.)to test its mechanical properties,taking hydrogen and elevated temperature environment into account.The main conclusions are as follows:(1)The influence of hydrogen on the plastic deformation of micropillar is mainly manifested in two aspects:for one thing hydrogen can activate more slip system and promote the occurrence of cross slip that makes the plastic deformation more uniform which mainly happens in pillars of(001)and(111)orientations,for another hydrogen makes it emission dislocations more frequently when a dislocation source is activated that makes the plastic deformation concentrated which mainly happens in pillars of(011)orientation.In addition,the slip of dislocation is more frequent while the distance of dislocation movement is reduced and the elastic modulus and yield strength of pillar are both increased with small amount of hydrogen.(2)Within the experimental temperature,it becomes more difficult for dislocation to cut~?phase when the test temperature rises,and that deteriorates the plastic properties of(001)and(011)oriented pillar by reducing activated slip systems so the plastic deformation of slip systems have great difference.For(111)oriented pillar the high test temperature will promote cross slip of octahedral plane so a zig-zagged slip plane can be observed in SEM.Moreover,dislocation motion distance increases at high temperature while the pillar's yield strength decreases,and the influence of temperature on elastic modulus of micropillar depends on its grain orientation.