| dc.description.abstract | Selective laser melting (SLM) manufacturing belongs to additive manufacturing and is one of the important emerging process technologies. Obviously, SLM has processing advantages over traditional manufacturing processes in prototyping of metal parts or manufacturing of complex shaped parts. A study of SLM manufacturing of Inconel 718 was carried out with four parameters namely laser power, scanning speed, hatching space and build orientation. The research is divided into two parts. Firstly, a larger process parameter range was designed for the prestudy test, and a reasonable parameter range was determined based on the formability and mechanical properties. Secondly, Taguchi and principal component analysis were used for single-objective and multiobjective optimizations respectively for optimizing tensile strength, impact energy, elongation, and hardness. The causal relationship among the process condition, metallographic structure, mechanical property and failure mechanism was discussed.
The results show that the optimal tensile strength of product can be obtained by using laser power 140 W, scanning velocity 800 mm/s, scanning spacing 70 m, and build orientation 45º in the single-objective optimization analysis. Tensile strength in the verification experiment was 1190 MPa. The results of multi-objective optimization analysis revealed that tensile strength and impact energy can be reinforced simultaneously. But tensile strength and elongation can’t be reinforced simultaneously. The optimal combination of process parameters with four mechanical properties as the strength index is exactly the same as that with tensile strength alone as the target. In the multi-objective verification experiment, the tensile strength was 1190 MPa, impact energy 82 J, elongation 27%, hardness HRC 33. If the volume energy density of the SLM process was similar, the one with higher power and higher scanning speed over-accumulated energy and form a large amount of dendritic or cellular crystals. Too much dendritic crystallization resulted in a decrease in tensile strength. In addition, the process using too low volume energy density led to porosity arising, so that the impact energy declined. | en_US |