The Study Of Laser Rapid Forming 316L/Inconel718 Functionally Gradient Materials

As an advanced coating method,laser cladding has been widely applied in the area of metal parts strengthening and remedy,which will enhance the wear and corrosion resistance of the parts.However the coatings directly deposited on the base material will result in stress concentration,which will limit the performance of coatings.Combining the technology of laser cladding with the concept of functionally gradient material(FGM) are proposed,this will not only make sure the excellent performance of cladding alloys,but also can release the stress concentration between base materials and cladding layers.In this paper,single element experiment,orthogonal experiment and Functionally Gradient Materials(FGM) experiment will be conducted using Laser Rapid Forming(LRF) technology.Then the microstructure,element distribution,microhardness distribution,friction coefficient and wear resistance will be tested by the means of optical microscope,electron microprobe,microhardness tester and microtribometer.In the end,the corrosion resistance is investigated.The research contents are as follows:(1) The single element experiment of laser rapid forming 316L stainless steel powders will be conducted,and the effects of main parameters such as laser power,scanning velocity,powder feeding rate on the shape of cladding layers'cross-sections will be discussed.(2) The orthogonal experiment will be carried out,in which the cladding layers width and height are taken as the dependent variables.And laser power,scanning velocity,powder feeding rate are regarded as arguments.The influence level of each arguments to dependent variables will be discussed by range analysis,and the regression model between arguments and dependent variables can be established by regression analysis.(3) Stainless Steel 316L/Inconel718 superalloy functionally gradient materials will be prepared and tested.It is indicated that the microstructure are very fine and fully dense,presenting a type of directional columnar dendritic growth.Meanwhile,the element and microhardness distribution show a linear function along the gradient direction.What is more,wear and corrosion resistance from stainless steel side to nickel alloy side strengthen gradually.The stainless steel base material and superalloy strengthening gradient coating is directly fabricated using laser rapid forming technology.This not only release the stress concentration between heterogeneous materials,but also realize the brilliant performances of reinforcing phase.