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Effect of annealing on the microstructure and properties of IN 625 specimens manufactured by selective laser melting

Sitek Ryszard, Ciftci Jakub, Moszczyńska Dorota, Maj Piotr, Ura-Bińczyk Ewa, Warzybok Piotr, Cieślik Iwona, Wiśniewski Paweł, Mizera Jarosław

Archives of Civil and Mechanical Engineering

2022

Vol. 22, no. 4

art. no. e207, 2022

The study examines the effect of the annealing on the microstructure, tensile strength (small flat dog-bone specimen size with 5 mm dimension of measuring base) and corrosion resistance of IN 625 nickel superalloy specimens manufactured by means of selective laser melting method (SLM). The annealing of such specimens was carried out in a chamber furnace in a protective atmosphere of argon at a temperature of 1038 °C for 1 h. The cooling process was carried out in an atmosphere of air at ambient temperature. The microstructure of the IN 625 nickel superalloy after the 3D printing process and after the post-process heat treatment (HT) was examined by means of scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results showed a uniform microstructure after the SLM process with element microsegregation. The cooling rate in the heat treatment was not sufficient which caused precipitation at the grain boundaries, most probably carbides and resulted in only a partial increase in ductility much lower than that of the material in initial state despite the high temperature applied during the annealing. The strength in the HT was on a level comparable to as-build state, 852 MPa and 891 MPa, respectively. Additional corrosion resistance tests were performed by the potentiodynamic method in a 3.5% NaCl solution at room temperature. HT increased the current density variation from ipass due to the formed precipitates. Our studies show that the size effect is an important factor when assessing the properties of IN 625 obtained using SLM. Despite similar microstructure, the structure defects play a more significant role which translates into lower mechanical properties than in normal sized specimens defined by the standard ASTM E8.

Texture, residual stresses and mechanical properties analysis in the commercial 1.4462 duplex stainless steel subjected to hydrostatic extrusion

Zdunek Joanna, Maj Piotr, Kulczyk Mariusz, Mizera Jarosław

Archives of Civil and Mechanical Engineering

2019

Vol. 19, no. 2

525--534

In the current research the hydrostatic extrusion (as one of the most common method of grain refinement) of the commercial 1.4462 duplex stainless steel was carried out using several reduction stages leading to a cumulative deformation strain ɛ = 1.4, and then ɛ = 3.8. The extrusion process has led to a change of microstructure and texture of the investigated material as was expected. Moreover, these changes were accompanied by improvements in mechanical properties measured by the nanohardness. The aim of this research was the characterization of the texture, residual stress and mechanical properties after subsequent stages of deformation.