Effect Of Carbon Content And Solid Solution Temperature On Microstructure And Mechanical Properties Of GH3230 Formed By Selective Laser Melting

Selective laser melting(SLM)technology can directly form components with complex structures without using molds,and has shown strong technical advantages in the field of manufacturing components with complex structures.In recent years,this technology has been used in the aerospace field.Based on the manufacturing of advanced military aero-engine combustion chambers,this paper systematically studied influence of carbon element content and heat treatment process on microstructure and high-temperature mechanical properties of GH3230 nickel-based superalloy formed by selective laser melting technology.The phase diagram's software JMat Pro was used to calculate the precipitation process of carbides.Finally,the strengthening mechanism of carbides on the alloy was discussed,and the alloy composition and heat treatment process was optimized.GH3230 superalloy's component with carbon content of 0.3%,0.15%and 0.08%(named230-1,230-2,230-3,respectively)was designed to investigate the effect of carbon content on the selective laser melting forming of GH3230 nickel-based superalloy's comprehensive influence of high temperature mechanical properties.Three kinds of GH3230 superalloy samples with different carbon content were prepared by the selective laser melting forming technology.Four solid solution heat treatment systems with temperatures of 1180?,1200?,1230?and 1250?were designed.According to four designed temperatures,the three-component laser melting forming GH3230 superalloy sample was solid-solution treated.After comparing and analyzing the microstructure morphology of GH3230 alloy formed by laser melting with three different carbon contents,it is found that with the increase of the solid solution temperature,the carbide size in the 230-1 and 230-2 alloys both increase first,then decrease and then increase.The carbide size is the smallest when the solid solution temperature is 1230?,and the carbide size is the largest at 1250?.While the carbide size in 230-3 alloy decreases with the increase of the solid solution temperature,and its carbide size is the largest when the solid solution temperature is 1180?,and the carbide size is the smallest at 1250?.As the carbon content in the alloy increases,the number of carbides in the alloy increases significantly.As the solid solution temperature increases,the number of carbides in the 230-1alloy does not change significantly,and the number of carbides in the 230-2 and 230-3 alloys is significantly reducing,and the tendency of number's reducing of carbides in 230-3 is more obvious than that in 230-2.The sample of 230-1 is precipitated two kinds of carbides,M₆C and M₂₃C₆,while 230-2 and 230-3 is precipitated only one kind of carbides,M₆C.With the increase of the carbon content in the alloy,the pinning effect of carbides is strengthened,and the grains become finer;with the increase of the solid solution temperature,the grain size of the 230-1alloy does not change significantly,while the 230-2 and 230-3 alloy grains are obviously larger.Among them,the larger becoming's tendency of 230-3 alloy grains is the most obvious.The high temperature tensile test results show that as the carbon content increases,the strength of the sample increases and the plasticity decreases.With the increase of the solution temperature,its strength and plasticity first increase and then decrease,and reach the highest at1230?,and the microhardness also has a consistent law.The results of observation and analysis of high temperature tensile fracture morphology show that the sample in the direction perpendicular to material building direction has the characteristics of"cleavage fracture";while the sample in the direction parallel to material building direction presents the characteristics of"along crystal fracture",and the fracture mode of the sample in the direction parallel to material building direction is ductile fracture.This indicates that the fracture mode of the three-component GH3230 sample at high temperature is mainly intergranular fracture.Based on the above analysis,it can be seen that when the solid solution temperature is1230?,the high temperature tensile mechanical properties of SLM formed GH3230 alloy are the best,the SLM formed GH3230 alloy with a carbon content of 0.3%has highest strength,and the carbon content of 0.08%has highest plasticity.