Research On Processes And Properties Of Hard-to-weld IN-738LC Superalloy Manufactured By Selective Laser Melting

Selective laser melting(SLM)is a rapid manufacturing method.Specimens are fabricated using metal powder and built layer by layer.Alloy IN-738 LC has excellent mechanical properties and 850? high work temperature.It belongs to the hard-to-weld superalloy due to the cracking-prone nature of the alloy whose chemical composition contains high amount of(Ti + Al)alloying elements.SLM is similar to the welding,and the alloy IN-738 LC is hard to be processed by SLM.It is a big challenge to form crack-free IN-738 LC samples fabricated by SLM.In this paper,IN-738 LC superalloy was used as the research object,the specimens is fabricated by SLM125 HL.The relative density,crack formation,microstructure and mechanical properties was investigated.A useful method of mitigating defects is studied through systematic investigations on the pre-processing,SLM optimization,and postprocessing of the material.Powder recoating ability was improved through sieving and powder drying,thus good formability was obtained.According to the relationship of the processing parameters and the resultant mechanical properties,the processing map was plotted,and the best processing parameters was determined.The tensile properties and the elongation of the as-printed specimens was 1010 MPa and 1.6% processed by the optimized processing parameters(270W,290mm/s).The appropriate temperature of hot isostatic pressing(HIP)was determined by the relationship of the relative density and mechanical properties of the specimens under different HIP temperature.It suggested that relative higher HIP temperature was better.The tensile properties and the elongation of the HIPed specimens was 1100 MPa and 3.9%.The appropriate heat treatment was determined by the relationship of the microstructure and mechanical properties of the specimens under different heat treatments.It suggested that double aging heat treatment(DAHT)was better than standard heat treatment(SHT).The tensile properties and the elongation of the DAHT specimens was 720 MPa and 14.4% at 850?.The cause of the crack formation was determined by the EDS results.It implies that the cracking may be attributed to the segregation of Ti at the grain boundary,and the results of Thermal-Calc confirmed that.In the end of the paper,a turbine blade part is printed to demonstrate the capability of SLM to form complex-geometry,good-quality IN738 LC superalloy.