Solid Particle Erosion of Nanocrystalline Nickel Coatings: Influence of Grain Size and Adiabatic Shear Bands
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INTRODUCTION
THE influence of the microstructure of metallic materials on their solid particle erosion resistance has been extensively investigated.[1–9] Grain size is one of the important microstructural parameters that cause the strength of the material to increase.[10] However, the influence of grain size on the solid particle erosion behavior of metallic materials has not been comprehensively investigated. In an earlier study,[11] the influence of grain size in the range of 30 to 1100 lm on the erosion of iron (Fe), copper (Cu), and titanium (Ti) was examined and it was concluded that the erosion rate was independent of grain size in iron and copper but not for Ti. However, the authors[11] concluded that the above grain size dependence in the case of Ti is actually
NITIN P. WASEKAR is with the International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Balapur PO, Hyderabad 500 005, India. PRATHAP HARIDOSS is with the Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras (IITM), Chennai 600 036, India. G. SUNDARARAJAN is with the International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI) and also with the Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras (IITM). Contact e-mail: [email protected] Manuscript submitted July 7 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
a reflection of the increased interstitial content (N and O) in Ti with increased annealing time employed to increase grain size. Subsequent to the above investigation (published in 1987), development of nanostructured materials with grain size in the nanometer range has gained great importance. A number of techniques have been developed to obtain nanostructured materials. Of these, pulsed electrodeposition (PED) is an elegant method to obtain nanostructured thick (up to 1 mm) coatings of a number of metals and alloys.[12–14] In addition, the PED process is versatile so as to obtain coatings that have different grain sizes within the nano-range.[13] In view of the above, the objective of this study is to characterize the influence of grain size (in the nanoregime) on the solid particle erosion (henceforth called erosion) behavior of Ni coatings. For the benchmarking purpose, the erosion data on bulk annealed Ni (43 lm grain size) have also been included. It needs to be highlighted that prior work on the erosion behavior of nanocrystalline materials does not exist in the open literature. Therefore, this paper presents the first and naturally original investigation on this subject. Further, the present paper aims at a comprehensive study of the influence of grain size on erosion by varying the grain size over a broad range in the nanocrystalline regime (20 to 200 nm).
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Ni by PED on a Ti substrate. Due to the poor adhesion between PED Ni and the Ti substrate, it was possible to remove the coating from the substrate by simple mechanical parting. For TEM studies, a 3-mm-diameter disk was punched out from the f
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