Microstructure And Mechanical Properties Of GH3536 Alloy Formed By Laser Solid Forming

In this paper,the GH3536 alloy formed by laser cladding(LSF)was taken as the research object,and its microstructure,tensile properties at room temperature and high temperature,fatigue crack growth properties under different stress ratios,and high temperature and low cycle at 800 °C were investigated.Fatigue performance was studied and the main conclusions were as follows:(1)The interior of LSF-formed GH3536 alloy is columnar crystals growing along the forming direction,and the precipitation phases are mainly M23C6 and M6 C carbides.The anisotropy of the tensile properties of the as-deposited samples at room temperature is mainly due to the difference in the microstructure of the alloy in different directions.,the mechanical properties along the forming direction are higher,and its tensile strength,yield strength and elongation are 855.3 MPa,581.2 MPa,and 19.7%,respectively.Solution treatment can promote the equiaxing of the internal grains of the alloy and eliminate the anisotropy of the alloy structure and tensile properties.At high temperature,the degree of anisotropy of the as-deposited sample decreases,the elongation becomes higher,and the fracture mode is ductile fracture above 500 °C,while the solid solution sample exhibits brittle fracture characteristics at high temperature.(2)The difference in fatigue crack growth resistance of LSF-formed GH3536 alloy as-deposited samples in different directions is mainly caused by the hindering effect of columnar grain boundaries on crack growth,and the fatigue crack growth rate of cracks perpendicular to the forming direction is lower.After solution treatment,the difference in microstructure of GH3536 alloy in different directions disappears,so the anisotropy of crack propagation disappears.The increase of the stress ratio will make the cracks in the alloy sample more inclined to expand inside the grains with smaller orientation difference,the number of deflections during the fatigue crack growth process is reduced,and the crack growth path becomes more straight,which in turn makes the fatigue crack growth.rate rises.(3)Under the condition that the total strain amplitude at 800℃ is±0.25%,the solid solution sample has a higher low cycle fatigue life,which is 3714 times.The increase of the total strain amplitude will significantly reduce the low cycle fatigue life of the alloy sample.The specimens at lower strain amplitudes are mainly characterized by cyclic stability during cycling.As the strain amplitude increases to ±0.8%,the specimens are first cyclically hardened and then cyclically softened.The Halford-Marrow plastic strain energy model at high temperature can accurately predict the low-cycle fatigue life of the GH3536 alloy,and the error between the prediction results and the experimental results is within10%.During the low-cycle fatigue cycle,the cracks of the alloy samples mostly originated from the surface defects and oxides of the samples,and with the increase of the stress amplitude,the number of crack sources also increased,which accelerated the failure rate of the samples.