Plastic Deformation in an Amorphous Ni-P Coating
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I.
INTRODUCTION
THE surface properties of materials play a crucial role in meeting various needs of industrial applications, such as corrosion resistance, wear resistance, nonmagnetism, and so on.[1–3] Optimizing the mechanical properties of the surfaces of metals and alloys is a key research area. To date, several surface-modification techniques, such as laser cladding,[4] electron-beam hardening,[5] plasma spraying,[6] and magnetion sputtering,[7,8] have been successfully developed to fabricate surface-coating materials to improve the surface properties of materials. In various kinds of coatings, nickelphosphorus (Ni-P) films are well-known protective coatings and are widely adopted for versatile industrial applications. Because of such properties as uniform thickness, high hardness, corrosion, and wear resistance, Ni-P films are used for such industrial applications as drills, taps, gears, sprockets, and similar devices requiring hardness and lubrication.[9] Recently, Ping et al.[9] successfully plated Ni-P coatings on a carbon steel with a mechanically assisted electroplating technique. Their results show that the Ni-P coatings electroplated with mechanical assistance have smoother
Y.F. SHEN, Associate Professor, and L. ZUO, Professor, are with the Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110004, P.R. China. Contact e-mail: [email protected] W.N. LIU and X. SUN, Senior Scientists, are with the Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352. W.Y. XUE, Engineer, is with the The State Key Lab of Rolling & Automation, Northeastern University, Shenyang 110004, P.R. China. Y.D. WANG, Professor, is with the School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, P.R. China. P.K. LIAW, Professor, is with the Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996. Manuscript submitted March 31, 2011. Article published online January 6, 2012 1610—VOLUME 43A, MAY 2012
surfaces with enhanced hardness and greater polarization resistance compared to the Ni-P coatings that are electroplated without mechanical assistance. Simultaneously, Chang et al.[10] proved that significant strengthening is induced by annealing electrodeposited Ni-P alloys with low phosphorus contents. They suggested that the phenomenon should be related to the relaxation at the nonequilibrium grain boundaries, the segregation of phosphorus at the grain boundaries, and possibly the reduction of the defect density in the grain interiors upon annealing. El Mahallawy et al. obtained Ni-P coatings on different magnesium alloys with an electroless-plating technique.[11] Unfortunately, the forming-ability test indicates that hot rolling of the coated substrate is not successful in keeping a continuous coating, because the coating cracks in both as-coated and heat-treated specimens, regardless of a great improvement in the corrosion resistance of t
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