Study On Laser Metal Deposition Process And Mechanical Properties Of 304L/IN625 Functionally Gradient Materials

Functionally graded materials are advanced engineering materials whose chemical composition and microstructure change with location,and are widely used in the aerospace,nuclear industry,and biomedical industries.Laser metal deposition is an advanced additive manufacturing technology commonly used in the preparation of functionally graded materials.The complexity of the internal components and structure of functionally graded materials places extremely high demands on the preparation process of laser metal deposition.Inappropriate laser metal deposition process parameters are prone to defects such as cracks,unmelted powder,and shrinkage porosities.Therefore,before using laser metal deposition technology to prepare functionally graded materials,a series of process optimization experiments need to be performed.The reasonable process parameter optimization process can quickly screen out the best process parameters and prepare functionally graded materials that meet the requirements of use.In this paper,304L/IN625 was used as the research object,and the laser metal deposition process of functionally graded materials were systematically studied.A laser metal deposition process parameter screening process was developed based on three types of melt profile features of single pass,horizontal overlap and vertical overlap.The optimal process parameters were determined,and the process parameters were verified by the performance analysis of functionally graded materials.The main research contents are as follows:(1)The phenomenon of powder separation of the premixed powder in the laser metal deposition process was investigated.A method for collecting and distinguishing pre-mixed powder particles was proposed;a pre-mixed powder ratio calculation model was established;the threshold for powder separation was determined;and whether the 304L/IN625 pre-mixed powder had powder separation phenomenon was quantitatively characterized.(2)Develop a screening process for laser metal deposition process parameters.Based on the single lane width,the parameters of the laser metal deposition process without powder separation were determined.Based on the morphological characteristics of the horizontal overlap melt and the vertical overlap melt,the relationship between cracks,melt fluctuations,unmelted powder,melt slope,and laser metal deposition process parameters were explored.Study the effect of laser metal deposition process parameters on the amount of powder used.Based on the evaluation criteria of powder separation,cracks,melt fluctuations,unmelted powder,melt slope and minimum powder consumption in the three types of melt channels:single pass,horizontal overlap and vertical overlap,the laser metal deposition process parameters of 304L/IN625 functionally graded materials are optimized.(3)304L/IN625 functionally graded materials were prepared based on the optimal laser metal deposition process parameters.(4)The performance of 304L/IN625 functionally graded materials were analysed.The microstructure,hardness distribution and tensile properties of 304L/IN625 functionally graded materials were explored.The influence mechanism of microstructural changes on mechanical properties was analyzed.The rationality of laser metal deposition process parameter optimization of 304L/IN625 functionally graded materials was verified.