A Study on the Corrosion and Wear Behavior of Electrodeposited Ni-W-P Coating
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WITH the ever-increasing demand for surface coatings for decoration and performance in industrial applications, electroplated binary alloy coatings cannot usually meet stringent requirements. For example, machinery used in corrosive environments, such as chemical pumps in the petro industry, orthopedic implants, food-processing facilities, and mining equipment, face combined issues related to corrosion and wear. Thus, research and development focused on ternary alloy coatings has been carried out.[1–3] Among the examined materials, Ni alloy coatings have been widely investigated. Although tungsten has excellent heat and corrosion resistance, it cannot be electrodeposited solely by the introduction of tungstate in the electrolyte. It must be co-deposited with other metals such as Ni, Fe, Co, or P in order to form an alloy coating.[4–6]
HUNG BIN LEE is with the Department of Materials Science and Engineering, Da-Yeh University, Changhua 51591, Taiwan, ROC. Contact e-mail: [email protected] MENG YEN WU is with the Department of Electrical Engineering, Da-Yeh University, Changhua 51591, Taiwan, ROC. Manuscript submitted November 3, 2016.
METALLURGICAL AND MATERIALS TRANSACTIONS A
In 1963, Pearlstein[7] became the first to prepare a Ni-W-P alloy via electroless plating. It the Ni-W-P alloy was demonstrated to have better heat resistance and mechanical properties than those of its Ni-P predecessor. Du and Pritzker[8] studied the effects of electrolyte compositions, pH, and temperature on the coating composition and deposition efficiency of the electroless Ni-W-P alloy. The electrolyte temperature and pH were found to be crucial factors. The importance of the mechanism of Ni2+ in the reduction of both W and P was demonstrated. However, they found that the W co-deposition usually decreased the P content in the coating and isolated the cracking that occurred with the formation of an amorphous microstructure.[9] Balaraju et al.[10] compared the phase transformations of the binary Ni-P and ternary Ni-W-P alloys prepared from electroless plating using differential scanning calorimetry measurements. They reported that the ternary alloy has a higher recrystallization temperature and therefore better high-temperature hardness than that of its binary counterpart. The co-deposited W in the coating impeded the precipitation and growth of Ni3P. Subsequently, the microstructure and mechanical properties were determined to be highly stabilized.[11–15] In terms of the corrosion resistance of the Ni-W-P alloy, de Lima-Neto et al.[16] reported that the electrodeposited Ni65W20P15 coating was crack-free following annealing and was more resistant to corrosion than
its chromium counterpart. Gao et al.[17] demonstrated that the Ni-W-P coating has performance better than that of the Ni-P alloy and that its corrosion performance improves at a higher P content. In terms of the wear performance, Palaniappa et al.[18] prepared a Ni-W-P alloy in an acidic electroless electrolyte and found that raising the W content of the coating could i
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