Abstract
The strength and ductility of microcrystalline and nanocrystalline tungstsen carbide-cobalt (WC-Co) cermets have been evaluated by employing a stored energy Kolsky bar apparatus, high-speed photography and digital image correlation. The test specimens were thin-walled tubular AI7075-T6 substrates 250 μm thick, coated with a 300 μm thick microcrystalline or nanocrystalline WC-Co layer with an average grain size of about 3 μm and 100 nm, respectively. Dynamic torsion experiments reported in this paper reveal a shear modulus of 50 GPa and a shear strength of about 50 MPa for both microcrystalline and nanocrystalline WC-Co coatings.
The use of high-speed photography along with digital image correlation has shown that damage to the coating coincides with a significant softening on the stress-strain curve. The coating failed in mode III, and strong interactions between the crack faces were probably responsible for the increase in load after failure of the coating. The overall failure of the coating-substrate system was not brittle but rather progressive and controlled by the ductility of the aluminum substrate.
A methodology for investigating damage kinetics and failure has been established. This methodology can be applied to examine the behavior of other advanced materials that can be manufactured as coatings on ductile substrates. Manufacturing coatings free of initial microcracks remains a significant challenge. Research on optimization of the spray deposition parameters should be pursued to produce high-quality nanostructured coatings that can fully exploit the benefits of nano-size grains.
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References
Hall, E.O., “The Deformation and Ageing of Mild Steel. 2. Characteristics of the Luders Deformation,”Proc. Phys., Soc. B. 64,747–753 (1951).
Petch, N.J., “The Cleavage Strength of Polycrystals,”J. Iron Steel Inst.,174,25–28 (1953).
Zhang, Z., Wahlberg, S., Wang, M., andMuhammad, M., “Processing of Nanostructured WC-Co Powder from Precursor Obtained by Coprecipitation,”Nanostructured Materials,12,163–166 (1999).
Kung, H. andFoecke, T., “Mechanical Behavior of Nanostructured Materials,”MRS Bulletin,24,14–15 (1999).
Weertman, J.R., Farkas, D., Hemker, K., Kung, H., Mayo, M., Mitra, R., andvan Swygenhoven, H., “Structure and Mechanical Behavior of Bulk Nanocrystalline Materials,”MRS Bulletin,24,44–50 (1999).
Nieh, T.G. andWadsworth, J., “Hall-Petch Relation in Nanocrystalline Solids,”Scripta Metall. Mater.,25,955–958 (1991).
Scattergood, R.O. andKoch, C.C., “A Modified-Model for Hall-Petch Behavior in Nanocrystalline Materials,”Scripta Metall. mater.,27,1195–1200 (1992).
Coble, R.L., “A Model for Boundary Diffusion Controlled Creep in Polycrystalline Materials,”Journal of Applied Physics,34,1679–1688 (1963).
Mayo, M.J., Siegel, R.W., Narayamy, A., andNix, W.D., “Mechanical Properties of Nanophase TiO 2 as Determined by Nanoindentation,”Journal of Materials Research,5,1073–1082 (1990).
Mayo, M.J., Siegel, R.W., Liao, Y.X., andNix, W.D., “Nanoindentation of Nanocrystalline ZNO,”Journal of Materials Research,7,973–979 (1992).
Nieh, T.G., McNally, C.M., andWadsworth, J., “Superplastic Behavior of a 20-Percent Al 2 O 3 /YTZ Ceramic Composite,”Scripta Metall. Mater.,23,457–460 (1989).
Nieh, T.G., Wadsworth, J., andWakai, F., “Recent Advances in Superplastic Ceramics and Ceramic Composites,”Int. Mater. Rev.,36,146–161 (1961).
Maehara, Y. andLangdon, T.G., “Superplasticity in Ceramics,”Journal of Materials Science,25,2275–2286 (1990).
Mayo, M.J., “High and Low Temperature Superplasticity in Nanocrystalline Materials,”Nanostructured Materials,9,717–726 (1997).
Espinosa, H.D. and Nemat-Nasser, S., ASM Handbook, Mechanical Testing and Evaluation, Vol. 8 (2000).
Ruiz, C. andMines, R.A.W., “The Hopkins Pressure Bar—An Alternative to the Instrumented Pendulum for Charpy Tests,”Int. J. Fracture,29,101–109 (1985).
Kobayashi, T., Yamamoto, I., andNiinomi, M., “Evaluation of Dynamic Fracture-toughness Parameters by Instrumented Charpy Impact Test,”Engineering Fracture Mechanics,24,773–782 (1986).
Eftis, J. andKrafft, J.M., “A Comparison of Initiation with Rapid Propagation of a Crack in a Mild Steel Plate,”J. Basic. Eng., Trans. ASME,87,257–266 (1965).
Prakash, V., Freund, L.B., andClifton, R., “Stress Wave Radiation from a Crack Tip During Dynamic Initiation,”Trans. ASME,165,356–365 (1992).
Subbash, G. and Ravichandran, G., ASM Handbook, Mechanical Testing and Evaluation, Vol. 8 (2000).
Nemat-Nasser, S., ASM Handbook, Mechanical Testing and Evaluation, Vol. 8 (2000).
Espinosa, H.D., Patanella, A., andXu, Y., “Dynamic Compressionshear Response of Brittle Materials with Specimen Recovery,” EXPERIMENTAL MECHANICS40,321–330 (2000).
Espinosa, H.D., Zavattieri, P.D., andDwivedi, S., “A Finite Deformation Continuum Discrete Model for the Description of Fragmentation and Damage in Brittle Materials,”Special Issue of Journal of the Mechanics and Physics of Solids,46,1909–1942 (1998).
Zavattieri, P.D., Raghuram, P., andEspinosa, H.D., “A Computational Model of Ceramic Microstructures Subjected to Multi-axial Dynamic Loading,”Journal of the Mechanics and Physics of Solids,49,27–68 (2000).
Kolsky, H., “The Propagation of Longitudal Elastic Waves Along Cylindrical Bars,”Phil. Mag.,45,712–730 (1954).
Espinosa, H.D., Patanella, A., andFischer, M., “Dynamic Friction Measurements at Sliding Velocities Representative of High-speed Machining Processes,”Journal of Tribology,122,834–848 (2000).
Espinosa, H.D., Patanella, A., andFischer, M., “A Novel Dynamic Friction Experiment Using a Modified Kolsky Bar Apparatus,” EXPERIMENTAL MECHANICS40,138–153 (2000).
Chu, T.C., Ranson, W.F., Sutton, M.A., andPeters, W.H., “Application of Digital-image-correlation Techniques to Experimental Mechanics,” EXPERIMENTAL MECHANICS25,232–244 (1985).
Bruck, H.A., McNeill, S.R., Sutton, M.A., andPeters, W.H., “Digital Image Correlation Using Newton-Raphson Method of Partial Differential Correction,” EXPERIMENTAL MECHANICS29,261–267 (1989).
Barthelat, F., Malukhin, K., andEspinosa, H.D., “Quasi-static and Dynamic Torsion Testing of Ceramic Micro- and Nano-structured Coating Using Speckle Photography,”Recent Advances in Experimental Mechanics, a special volume in honor of Professor I.M. Daniel, 14th US National Congress of Theoretical and Applied Mechanics, 23–28 June, Blacksburg, VA, Kluwer, Dordrecht (2002).
Espinosa, H.D., ONR Report, Award No N00014-97-1-0550 (2001).
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Barthelat, F., Wu, Z., Prorok, B.C. et al. Dynamic torsion testing of nanocrystalline coatings using high-speed photography and digital image correlation. Experimental Mechanics 43, 331–340 (2003). https://doi.org/10.1007/BF02410532
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DOI: https://doi.org/10.1007/BF02410532