Test And Analysis Of Residual Stress On Nickel Based Single Crystal Superalloy In Different Orientations

There are many possibilities to induce residual stress in Ni-base single crystal superalloy during the manufacture and service procedures. The residual stress combined with the applied stress will affect the microstructure and mechanical performance significantly. Finite Element Method and Convergent Beam Electronic Diffraction have been extensively used to study the stress state in Ni-base single crystal superalloy, but X-ray diffraction (XRD) method and neutron diffraction which have been used wildly for the stress measurement in polycrystal haven’t been applied wildly.The aim of this work is to study the residual stress in Ni-base single-crystal superalloy by XRD.First of all, according to the crystal plane diffraction theory, using the X-ray diffraction to test sample’s [001] azimuthal (Ψ0,Φ0), according to (Ψ0, Φ0), to adjust the position of the sample fixture, seeking to obtain the crystal surface.Again, the different orientations of the three groups (1#,2#,3#) nickel-base single crystal superalloy tensile creep under the condition of220MPa/1000℃. tensile creep deformation microstructure of the sample was observed by SEM, you can see they’phase directional coarsening flat raft of tissue formation. Since all three samples were deviated [001] direction0°,10°,18°, so the raft of tissue growth direction is also different,1#sampley’phase raft of tissue perpendicular to the loading direction, the2#sample and3#sampley’phase raft of tissue deviate to perpendicular to the loading direction of about10°nd18°respectively. Raft of tissue homeostasis in the early development stage of creep deformation, flat-shaped y’phase raft of tissue to effectively improve the ability of nickel-based superalloy single crystals of high temperature deformation resistance. Raft of the tissue is not very stable when carried to the late creep, residual stresses accumulate inside the alloy, lead alloy quick break, flat raft of rules of the tissue has been severely damaged.According to XRD, we analyze that:in the process which from the start of creep to fracture of samples, the three principal stresses of the sample in different orientations have the overall macro-trends which are tensile stress of beginning to creep into pressure tensile stress at break. When stretched to breaking, the of1#sample and2#sample have the similar stress σ11, the stress of3#samples is smaller. The results of the experiment with the length of the sample rupture life coincided,1#and2#specimen samples have the shorter lifetime, respectively35.33h and36.52h, the residual compressive stress is large;3#sample has smaller residual compressive stress,has the longest lifetime and which has the lifetime of39.37h. Under normal circumstances, the <001> direction of the nickel-base single crystal superalloy has the best overall performance, deviate from the <001> direction farther, overall performance is worse. The results of this experiment is just the opposite, the reason may be due to the composition and heat treatment process for preparing a single crystal affects the properties of the material, while XRD analysis showed that stress, creep rupture, the σ22of3#sample remains tensile stress state, and the σ22of1#and2#samples converted to compressive stress, which may be the reason of the three samples about the difference.