Optimization Parameters of Milling Process of Mould Material for Decreasing Machining Power and Surface Roughness Criteria

Improving milling performances is an effective solution to decrease the costs required. This paper addressed a multi-response optimization to simultaneously decrease the machining power consumed Pm, arithmetical roughness Ra, and ten-spot roughness Rz. The Grey-Response Surface Method-Multi Island Genetic Algorithm (GRMA) consisting of grey relational analysis (GRA), response surface method (RSM), and multi-island genetic algorithm (MA) was proposed to predict the optimal parameters and yield optimum milling performances. The experimental trials were conducted with the support of a CNC milling center. The influences of spindle speed (S), depth of cut (ap), feed rate (fz), and tip radius (r) were explored using GRA. The nonlinear relationship between machining parameters and grey grade (GG) model was developed using RSM. Finally, two optimization techniques, including desirability approach (DA) and MA were performed to observe the optimal values. The results indicated that the machining power was greatly affected by processing factors and the radius has a significant impact on the roughness criteria. The measured reductions using optimal parameters of Pm, Ra, and Rz are approximately 77.05%, 50.00%, and 58.02%, respectively, as compared to initial settings. The GRMA can be considered as an effective approach to generate reliable values of processing conditions and technological performances in the milling process

Effects of scanning methods on cracking, microstructures and microhardness of Inconel 625 parts formed by direct laser metal deposition

This study aims at investigating the effects of scanning methods on the stress distribution and microstructures of Inconel 625 thin-walled part fabricated by direct laser metal deposition. The results showed that with the single direction scanning (SDS) method, the residual stress at both the ends of the thin wall was relatively high while the stress at the middle was smaller with a stress difference of about 1800 MPa. In contrast, with the reverse direction scanning (RDS) method, the residual stress in the thin wall was distributed relatively evenly, with a stress difference of about 350 MPa between both the ends and the center. The experimental results showed that, in the SDS method, cracks occurred at both ends and in the middle of the thin wall, whereas in the RDS method, warping and cracks phenomena were eliminated. The microstructure of the Inconel 625 in the forming layer is characterized by a columnar crystal structure that has a small length and grows perpendicularly to the scanning direction. This growth is continuous between the forming layers. In both cases, the microhardness increases with the height of the formed layers. The microhardness values are relatively uniform with values ranging from 420 to 450 HV

Wire and arc additive manufacturing of 308L stainless steel components: Optimization of processing parameters and material properties

International audienceIn the current study, wire and arc additive manufacturing (WAAM) of thin-walled 308L stainless steel components was reported. Firstly, the influence of the welding current, the voltage, and the travel speed in the WAAM process on the geometry of single weld beads was investigated. These parameters were also optimized for the deposition of 308L steel walls. Secondly, the microstructure and the mechanical characteristic of WAAM 308L steel walls have been explored. The obtained results reveal the optimized that parameters giving the desirable geometry of single weld beads for building 308L walls by the WAAM process. The microstructure of WAAM 308L steel walls mainly features the dendrites of austenite growing vertically and residual ferrite existing in grain boundaries of the austenite matrix. The microhardness of the built material is about 163 HV0.1. The UTS, YS and elongation of WAAM 308L walls are 532–553 MPa, 344–353 MPa, and 40–54%, respectively, which are relatively similar to those of wrought 308L stainless steel (UTS: 530–650 MPa, YS: 360–480 MPa, and elongation: 35–45%). Thus, the mechanical properties of WAAM 308L steel walls are considered to be adequate for industrial applications