ساخت، مشخصه‌يابي و ارزيابي رفتار تريبوخوردگي نمونه‌هاي فولاد زنگ‌نزن AISI 316L به روش ساخت افزايشي مبتني بر سيم و قوس (WAAM)

In recent years, the wire arc additive manufacturing (WAAM) process has been introduced as a competitive alternative for producing large metallic components with a high deposition rate an‎d lower cost. Despite these advantages, the layer-by-layer nature of the WAAM process an‎d repeated thermal cycles lead to the formation of a non-uniform thermal history an‎d, consequently, the development of microstructural anisotropy an‎d functional property inhomogeneity along the build height; a phenomenon that particularly affects hardness, corrosion, an‎d tribocorrosion behavior an‎d limits the application of these components in corrosive environments. The main objective of this research is to investigate the effect of heat input, controlled through the welding current, on the microstructure, microhardness distribution, an‎d degradation resistance, including corrosion an‎d tribocorrosion, of AISI 316L stainless steel components produced by conventional an‎d WAAM methods. For this purpose, two optimized parameter sets with different currents were selec‎ted after conducting single-pass experiments. Final samples were extracted from the bottom, middle, an‎d top regions of the components, an‎d their behavior was compared with each other as well as with a rolled sheet sample. Microstructural characterization was performed using optical microscopy, scanning electron microscopy, an‎d X-ray diffraction. Electrochemical corrosion behavior was investigated by electrochemical impedance spectroscopy an‎d potentiodynamic polarization tests in a 0.1 M hydrochloric acid solution, an‎d tribocorrosion performance was eva‎luated using a reciprocating test under a load of 20 N in the same solution. The results showed that the microstructure of the WAAM components consisted of a dual-phase austenite an‎d ferrite structure, an‎d the ferrite morphology changed from a lath-like structure in the lower regions to a skeletal structure in the upper regions along the build height. Microhardness continuously decreased from the bottom to the top, an‎d the sample produced with a lower current exhibited overall higher hardness than the sample produced with a higher current due to lower heat input an‎d the formation of a finer dendritic structure. In terms of localized corrosion, the WAAM samples exhibited higher resistance compared to the sheet sample. This improvement was attributed to the elimination of coarse MnS sulfide inclusions an‎d the absorption of sulfur by the ferrite present in the microstructure of these samples. In addition, the best tribocorrosion performance was observed in the upper region of the sample produced with the lower current, indicating a high capability for rapid re-passivation of the protective surface layer. Overall, the results of this study indicate that precise control of welding current an‎d management of the thermal gradient play a key role in improving the microstructure, hardness, an‎d resistance to corrosion an‎d tribocorrosion of AISI 316L stainless steel components fabricated by WAAM.

مسعود عطاپور , ابوذر طاهري زاده

بهزاد نيرومند , عباس بهرامي