On the formation of pileups during nano-scratching of Inconel 718 produced using additive manufacturing

The objective of this work is to understand the role of microstructure on pileup formation during nano -scratching of additively manufactured nickel superalloy, Inconel 718 (IN718). Scratches with median depths of & SIM;50 nm were made on as-received and solution annealed IN718 under the action of small normal forces using a spheroconical diamond indenter. The surface profiles of these scratches were then quantified using atomic force microscopy. The as-received IN718 showed a positive correlation between pileup height, and scratch depth. In contrast, the solution annealed IN718 specimen exhibited a negative correlation between pileup height, and scratch depth. Analysis of this observation involved experimental quantification of microstructure using electron back scatter diffraction, quantitative atomic force microscopy, in addition to complementary finite element simulations. Following analysis, we propose that this switchover originates due to differences in strength, hardening, and deformation localization characteristics of as-received and solution annealed IN718.