iTSSe TSS ADVANCED MATERIALS & PROCESSES | MARCH 2026 49 iTSSe TSS CHARACTERIZING DEFORMATION BY POSITRON ANNIHILATION SPECTROSCOPY: COLD SPRAY VERSUS HIGH-PRESSURE TORSION Jakub Cizek, Oksana Melikhova, Matej Jakubik, Jan Medricky, Filip Stefanik, Frantisek Lukac, Jan Cupera, Jozef Vesely, Rinat K. Islamgaliev, and Jan Cizek In this study, the positron annihilation spectroscopy method was used to characterize the microstructure and quantify the open-volume defects in four cold sprayed metals: Al, Cu, Ni, and Ti. As counterparts, bulk samples of these materials with ultra-fine-grained structures were also produced by high-pressure torsion, a process exceeding cold spray in the total deformation, but having several orders of magnitude smaller strain rates, and by a traditional cold rolling process. (Fig. 1) The Journal of Thermal Spray Technology (JTST), the official journal of the ASM Thermal Spray Society, publishes contributions on all aspects— fundamental and practical— of thermal spray science, including processes, feedstock manufacture, testing, Fig. 1 — Cold spray (CS) and high-pressure torsion processes (own schematics). While both result in heavily deformed microstructures, the CS process exhibits several orders of magnitude higher strain rates. and characterization. As the primary vehicle for thermal spray information transfer, its mission is to synergize the rapidly advancing thermal spray industry and related industries by presenting research and development efforts leading to advancements in implementable engineering applications of the technology. The highlighted papers below were hand-picked by Editor-in-Chief André McDonald. In addition to the print publication, JTST is available online through link.springer.com. For more information, visit asminternational.org/tss. TRIBOLOGICAL PROPERTY OF FLAMESPRAYED PEEK AND CFs/PEEK NANOCOMPOSITE COATINGS WITH ONE-, TWO-, AND THREE-DIMENSIONAL CARBON NANO-FILLERS Yupeng Li, Shuolei Zhang, Taihe Liang, Hongxu Song, Sai Wang, Lai Wei, and Mingkai Lei Polyether ether ketone (PEEK) nanocomposite coatings with diverse dimensional carbon nano-fillers to achieve low friction and low wear of moving mechanical parts in severe application conditions were not the same as the bulk polymer nanocomposites due to their special manufacturing processes. Herein, the flame spray processes were utilized to fabricate the PEEK and carbon fibers/PEEK (CFs/PEEK) nanocomposite coatings with one-dimensional carbon nanofibers, two-dimensional graphene nanosheets, and three-dimensional graphite nanoparticles in contents of 1.0 and 5.0 wt%. (Fig. 2) Fig. 2 — Real-time captured image of CFs/PEEK composite powders. FEATURE JTST HIGHLIGHTS
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