Impact of Abradant Size on Damaged Zone of 304 AISI Steel Characterized by Positron Annihilation Spectroscopy
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TRODUCTION
BLASTING is a surface treatment process (STP) useful in a wide spectrum of applications. The abrasive particles in the stream of compressed air leave the nozzle and hit material interacting with a surface. This process is often applied in the cleaning of industrial objects such as boat hulls, bridges, parts of machines, and cars to remove corrosion and achieve expected roughness of denture at the preliminary stage. Blasting makes it possible to treat complicated shapes with areas unreachable by polishing. Hence, it has found application in stomatology to excise deposits on teeth and discolorations. In addition to altering the surface, blasting also introduces changes in the near-surface region creating the damage region called a subsurface zone. This zone contains plastic layers and elastic deformations which modify its microstructure properties.[1] As a result, the local disorders as well as cracks can be generated leading to wear and debris generation. Impact of a given type of STP on the subsurface zone and its evolution beneath the worn surface is still an active research problem in the field of material engineering. This kind of investigation of the subsurface zone is usually performed using conventional engineering methods e.g., microhardness
P. HORODEK, K. SIEMEK, and J. DRYZEK are with the Institute of Nuclear Physics Polish Academy of Sciences, 31342 Krako´w, Poland. Contact e-mail: [email protected] M. WRO´BEL is with the AGH University of Science and Technology, 30 Mickiewicza Ave., 30-059 Krako´w, Poland. Manuscript submitted April 12, 2018. Article published online December 12, 2018 1502—VOLUME 50A, MARCH 2019
tests[2] and other analytical techniques like Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD). However, some changes causing the generation of lattice defects occur also at the atomic level. Their presence is hardly observed by the mentioned methods. Positron annihilation spectroscopy (PAS) is a sensitive tool for detection of open-volume defects such as vacancies, their clusters, dislocations, nano-voids, etc. PAS techniques deliver information about the kind of defects, their size and concentration. The successful application of this method to studies of subsurface zone has been proven in numerous studies.[3] Blasting can be characterized by many parameters such as angle, pressure, size, or type of abrasive particles and process duration. Thus, changes generated on and below the surface can be strongly dependent on these features. It should be also mentioned that blasting is a popular STP leading to nanocrystallization.[5] Treated material is subsequently annealed and the produced nano-size grains improve surface properties. Introduced dislocations are the basis of this process.[6] Hence, the above can be regarded as the additional field of blasting application. 304 AISI stainless steel was chosen as the object of studies because it is a very popular material in industry, and also an alloy common in research. Their properti
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