Study On The Forming Techniques And Mechanical Properties Of Inconel 625 Nickel-based Superalloys By Selective Laser Melting

Selective Laser Melting(SLM)is one of the most important technology in additive manufacturing.The SLM process can produce full-density metal parts with short production cycles and have a great potential in aerospace field,especially materials that are difficult to form in conventional methods,such as nickel-based superalloys.The technology of SLM with Inconel 625 nickel-based superalloys powder is still immature in foreign countries as well as in domestic.Based on this,Inconel 625 superalloys powder was used in this paper.The SLM bulk forming techniques were studied at forward LM 120 machine.It can provide technology reference for forming of Inconel 625 alloy workpiece by SLM method.In this paper,the Inconel 625 blocks with different process parameters were prepared by SLM method.The effects of laser power,scanning speed,scan interval and powder thickness on the mechanical properties of Inconel 625 superalloys were investigated,including relative density,microhardness and other mechanical properties.Then the process parameters were optimized,and a high density and high hardness nickel-based superalloys sample was obtained.The tensile properties of the optimized four sets of parameters were measured,and the fracture morphology was analyzed.The formation mechanism of defects such as holes,cracks and spatters in SLM forming process was analyzed,and the control measures of defects were put forward.Finally,the microstructure of SLM formed Inconel 625 block was analyzed.The results show that the density and hardness of Inconel 625 sample were increased with the decrease of scanning speed,layer thickness and scanning distance,as well as the increase of laser power.The tensile strength and yield strength both higher than the standard value,but the elongation after fracture is low,there are small and shallow fracture fissures;The dendritic grain reduced and the cellular grain increased with the decrease of the scanning speed,as well as the grain size was finer.The dendrite and cellular sub-grain were mainly formed in the SLM forming samples,and the size of sub-grains was between 0.5 and 1.5 ?m.In the sub-grain structure,the Mo and Ni elements in the cell boundaries were significantly higher than those in the intracellular.