Study Of Process And Mechanical Properties Of GH4169 Alloy By Laser Metal Deposition

GH4169 high temperature alloy has excellent properties of heat corrosion resistance,oxidation resistance and fati gue resistance above 600°C,so it is widely used in aerospace and other fields.However,traditional processing and manufacturing methods are difficult to meet the requirements of precision parts,and it is difficult to manufacture components with complex geometry,and processing GH4169 alloy is easy to cause tool wear and increase production costs.Laser Metal Deposition(LMD)is becoming a new manufacturing method for GH4169 high-temperature alloys because of its high forming efficiency,high processing f lexibility,no tooling restrictions,direct forming of required parts,and less post-processing compared to traditional processing methods.In this paper,the effects of two scanning strategies,unidirectional scanning and orthogonal scanning,on the structure and mechanical properties of GH4169 alloy deposited specimens were investigated by using laser melting deposition technology.By sieving and recycling the r esidual powder generated during laser melting deposition,the effect of different cycles of pow der recycling on the structure and properties of GH4169 alloy deposited specimens during laser melting deposition was investigated.The main studies are as follo ws:The effect of LMD scanning strategy on the organization and properties of the prepared GH41 69 alloy was investigated.The study showed that: The deposited layers of GH4169 alloy prepared by laser me tal deposition were organized as columnar crystals,which showed continuous epitaxial growth even through multiple deposited layers under the unidire ctional scanning strategy,and the continuous growth of column ar crystals was suppressed under the orthogonal scanning strategy.SEM revealed that the phase composition of the two scanning paths was basically the same,with the matrix being the γ phase and a large amount of Laves phase precipitated between the dendrites.The average primary dendrite arm spacing(PADS)was reduced from 7.65 μm in the unidirectional scan to 3.88μm in the orthogonal scan,and the orthogonal scan was favorable t o reduce the precipitation of Laves phase.The microhardness was reduced from 337 HV in the unidirectional scan to 316 HV in the orthogonal scan.In addition,the longitudinal porosity of the specimens deposited by the unidirectional scan strategy was 0.1%,which was higher than that of the specimens deposited by the orthogonal scan strategy of 0.07%,and the tensile strength and yield strength of the orthogonal scan were higher than those of the unidirectional scan.A study was conducted to test the effect of recycling GH4169 alloy LMD powder.The test results showed that: With the increase of the number of powder recycling,the average particle size of the powder tends to increase,from 59.861 um of the original powder to 64.144 μm after four cycles,and accompanied by powder burnout and satellite ball phenomenon.The elemental content of the powder changed with the increase of the number of cycles,among which the elemental content of Nb increased significantly from 4.31wt% of the original powder to 7.97wt% after four cycles,the proportion of Laves phase in the deposited state increased,the porosity and pore size increased,the tensile strength of the specimen decreased from1046 MPa of the original powder to 936 MPa,the tensile strength decreased by 10.5%.Powder recycling can lead to powder aging and reduce the mechanical properties of the laser metal deposited formed parts.