Research On Fiber Laser Additive Manufacturing Tecnology Of IN718Superalloy

Laser additive manufacturing(LAM) or three-dimensional printing based ondifferential geometry thought which allow to directly fabricate solid elements from3D CAD models in a layer-by-layer manner by laser. The main advantages of thistechnique are with no abrasive, high versatility, high flexible, short processing cycle,any complex shaped components with compact property and high performance canbe produced, and it has also advantages of low cost, excellent physical and chemicalproperties for manufacturing, especially for small runs. Currently, this technique istypically applied for aerospace, energy sources, automotive and biomedicalindustrial sectors.IN718alloys with excellent elevated temperature property iswidely used in important parts of aviation fields. To produce IN718superalloy,traditional processing methods with high cost not only can’t produce complexcomponents, but also makes the tool worn. However IN718superalloy deposited bylaser additive manufacturing with low cost is unlimited, and this method can also beapplied to repair and rebuild worn or damaged components. According to theparticularity of LAM, the quality of material, the parameters of laser beam, thestability of the process and technics standard must suit higher request. Therefore, inthis work a study on process, structure and properties of a Ni-based IN718alloyas-deposited by LAM, is presented.The basic intent of this article is to avoid oxide layer on the welding materialwith the protection of argon during depositing IN718alloy by LAM. Study foundthat powder feed rate is main factor of monolayer deposition height and monolayerdeposition width is mainly affected by the laser power. In addition, the height andwidth of multilayer deposition are strongly governed by Z that is the increment inthe Z direction and heat input.This paper is concentrated on the structure of IN718alloys as-deposited byLAM.With a thin layer of equiaxed grains on the top, as-deposited LAMcomponents make the micro-tissue well-distributed and compact, and Longcolumnar crystal throughout the as-deposited layers appears. The study found thatthe tensile property of as-deposited LAM components is closely related to the sizeof columnar crystal and the forced direction. Hence properly adjusting processingparameters (increasing power, preheating temperature and scanning speed) isconductive to epitaxial growth of columnar crystal. In addition, changing thescanning speed can also control the growth angles of the columnar crystal. Therefore,we can achieve excellent properties of forming parts through controlling the growth of columnar crystal.In order to obtain a fine dispersion of γ″precipitates (besides the commonsuperalloy γ′precipitates) in the face centered cubic Ni matrix γ instead of Lavesphase, heat treatment is necessary. By optimizing heat treatment process(homogenization treatment, solid solution treatment, double aging treatment), asignificant increase in mechanical properties was noted in the test result: tensilestrength was44%higher (from900MP to approximately1300MP) and yieldstrength was100%higher(from500MP to about1000MP) that is close to the levelof casting components was obtained disappointedly. Meanwhile, the averagehardness after heat treatment was significantly higher than as-deposited one.