Usinagem de materiais fabricados por manufatura aditiva por deposição de arco (MADA) com e sem alívio de tensão

Abstract

Additive manufacturing has established itself as one of the main technologies of Industry 4.0, enabling the production of metal parts through controlled layer-by-layer material deposition. Among the different processes, the use of arc welding techniques, such as MIG/MAG, stands out, enabling the manufacture of medium and large components with a high deposition rate. However, due to the intrinsic characteristics of the process, in which the resulting irregular surface, wide tolerances and poor finishing, subsequent machining operations are necessary to ensure better accuracy and finishing or workpieces. This work aimed to evaluate the machinability of two tubes manufactured by additive manufacturing using the MIG/MAG process with A5.28 ER90S-B3 wire with a 90 mm diameter x 120 mm length x 9 mm thickness. One of the workpieces was subjected to a residual stress relief test using the post-deposition vibration method. The same machining parameters were used for both parts. Two cutting speeds (vc) were varied (56 m/min and 140 m/min). Feed and depth of cut were kept constant in all tests (f = 0.05 mm/rev. and ap = 0.5 mm). Test were carried out with coolant. To evaluate the surface integrity of workpieces, the roughness (Ra and Rt), microhardness and microstructure below the machined surface were analyzed. Tool wear was also monitored. The results showed that the part subjected to post-treatment by vibration presented lower surface roughness values. For a cutting speed of 56 mm/min, there was a 27% reduction in the Ra parameter, while for 140 mm/min the reduction was 47%. As for microhardness, post-stress relief treatment contributes to a decrease in the average hardness of the deposited and stress-relieved sample, dropping from 306 HV (conventional deposition) to 271 HV (vibration stress relief). However, after the turning processes, the average hardness of the conventionally deposited sample increased regardless of the cutting speed. A lower tool wear rate was observed after machining the part subjected to stress relief treatment, reinforcing the potential of the technique as a viable alternative for improving machinability of the material made by MA tested in this work.