Investigation On Preparation Technology,Microstructure And Properties Of Inconel 939 Nickel-Based Superalloy Processed By L-PBF

Laser additive manufacturing has unique advantages in forming high-complexity parts,realizing topology optimization of complex parts,reducing assembly steps to achieve integrated forming,and has been widely used in various fields,especially in the aerospace field.Inconel939 nickel-based superalloy has high strength,corrosion resistance and oxidation resistance,and is widely used in gas turbine blades.In this paper,laser powder bed fusion technology was used to prepare nickel-based superalloys with Inconel 939 powder.The additive forming process,microstructure and mechanical properties of the alloy were studied.The specific research contents and results are as follows:(1)The effect of laser process parameters on the forming quality of Inconel 939 alloy prepared by laser powder bed fusion was explored.The results show that defects such as holes,unfused and cracks are mainly generated during the forming process.Samples exhibited best forming quality when the laser energy density is in the range of 40 J/mm~3 to 100 J/mm~3 and the relative density is above 96%.(2)The microstructure of the additively manufactured Inconel 939 alloy under different process parameters were studied.High laser power and scanning speed are conducive to the growth of columnar crystals.The growth of dendrites is controlled by the maximum temperature gradient and the preferred orientation mechanism.A<001>//X texture will form when using a scanning strategy of layer-by-layer rotation of 0°,while highly oriented three-dimensional texture of<001>parallel to the X,Y,and Z axes will form when layer-by-layer rotation of 90°is used,and a complex three-dimensional texture will form with rotation of 67°.(3)The tensile properties of the additively manufactured Inconel 939 alloy under different process parameters were studied.With the increase of laser power,scanning speed and scanning distance,the strength and elongation of the alloy increased firstly and then decreased.With the laser power of 95W,the scanning speed of 950 mm/s,and the scanning spacing of 0.07 mm,good tensile properties with a tensile strength of 1146 MPa and an elongation of 14.9%was achieved.(4)The effect of heat treatment on the microstructure and mechanical properties of additively manufactured Inconel 939 alloy was investigated.After heat treatment,recrystallization and grain growth occurred in the alloy,and the dislocation density decreased.The fineγ’phase and carbides precipitated and the volume fraction of the precipitations increased.the tensile strength of the alloy increased but the elongation decreased.The room temperature tensile strengths of the alloys after solution+single-step aging and solution+three-step aging heat treatment are 1332 MPa and 1251 MPa,respectively,which are 16.2%and 9.2%higher than those of the as-deposited alloys,and 26.9%and 19.1%higher than those of the conventional as-cast alloys.The tensile strengths of the heat treated alloys at 750℃is966 MPa and 832 MPa,respectively,which are better than that of cast Inconel 939.After heat treatment,the alloy has excellent high temperature hot corrosion resistance.After 150 h of high temperature hot corrosion,the weight loss of the alloy under the two heat treatment processes is 41.36 mg/cm~2 and 15.73 mg/cm~2.