Investigation on tribo-mechanical characterization of heat-treated LPBF-based Scalmalloy parts under certified conditions

A key component of automotive and aerospace applications is Scalmalloy components, which are produced using the laser powder bed fusion (LPBF) process. However, alternative cooling conditions were used during the heat treatment process to enhance the performance of the Scalmalloy parts. This research investigated the nano-level, tribo-mechanical and microstructural properties of the heat-treated Scalmalloy parts. In this study, Scalmalloy was heat treated at 325 degrees C for 4 h and then cooling was performed under different conditions such as cooling in the furnace, air and water (FC, AC and WC, respectively). The development of Al3(Sc, Zr) nano-precipitates in the < 111 > , < 200 > , and < 220 > lattice planes was verified by XRD. OM and FESEM analysis confirmed that the heat-treated Scalmalloy under the WC condition possessed enhanced grain refinement compared to the other conditions. Moreover, EBSD analysis also substantiated the phenomenon observed during the microstructural analysis. It was also confirmed that heat-treated Scalmalloy with the WC condition had a reduced grain size of 5.5 mu m which was 74% and 66% lower than the FC and AC conditions, respectively. This grain refinement was attributed to the improved nano-hardness of 3.2 GPa with a minimum indentation depth of 19.45 nm, which was 69% and 41% lower than the FC and AC conditions, respectively. Similarly, nano-wear analysis also confirmed that the WC condition showed a maximum COF of 0.81 and 49% enhanced wear resistance with a minimum worn-out depth and pile-up of - 78.16 nm and 48.41 nm, respectively. Further, various wear mechanisms such as abrasion, oxidation and delamination were also examined based on the worn-out surface of the wear specimens. Tensile performance revealed that the WC condition possessed a more brittle fracture with a maximum tensile strength of 535 MPa, whereas the FC condition displayed a more ductile fracture with a maximum elongation of 10%. These differences in their fracture mechanics justified the grain refinement of the heat-treated specimens with different cooling conditions.