Electroless Ni–P/Ni–B–B4C Duplex Composite Coatings for Improving the Corrosion and Tribological Behavior of Ck45 Steel

Mohsen Rezagholizadeh, Mohamad Ghaderi, Azam Heidary, and Seyed Mahmood Monir Vaghefi

 Abstract—Ni–P/Ni–B–B4C duplex composite coatings were deposited on Ck45 by electroless plating process, and their structure, morphology, micro hardness and corrosion resistance were evaluated. The duplex coatings were prepared using dual baths (acidic hypophosphite– and alkaline borohydridereduced electroless nickel baths) with Ni–P as the inner layer. The coatings were amorphous in asplated condition and nanocrystallized, and produced nickel borides upon heattreatment. SEM observations showed that the duplex interface on the Ck45 was uniform, and the compatibility between the layers was good. The Ni–P/Ni–B–B4C coating’s microhardness and corrosion resistance of Ni–B–B4C coating as the outer layer were higher than Ni–P coatings. The Ni–P/Ni–B–B4C duplex composite coatings with high hardness and good corrosion resistance properties would expand their scope of applications.

DOI: 10.1134/S207020511502015X

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Study of Hot Corrosion Resistance of Electroless Nickel Coating with Different Content of Phosphorous in Molten Salt Deposit Na2SO4–NaCl at 650°C

M. Ghaderi *, M. Rezagholizadeh, H. NasiriVatan and R. EbrahimiKahrizsangi

Abstract—In this research, the hot corrosion behavior of electroless nickel(۴, ۷, ۹, and 12 wt % P) was studied in 70 wt % Na2SO4–۳۰ wt % NaCl (3 and 6 mg/cm2) molten salt on a copper substrate. After being plated with a thickness of 25 ± ۳ μm, the specimens were annealed at 400°C for 1 hour, and then the hardness of each was measured by the Vickers hardness test method. The hot corrosion test was performed at 650°C for 20 hours inside the furnace at a rate of 4°C/min under atmospheric conditions. The results showed that Ni–۷ wt % P and Ni–۱۲ wt % P electroless coatings included the highest and the lowest hot corrosion resistance, respectively. The difference in the weight increase of the hot corrosion of Ni–۱۲ wt % P coating was about 8 times as much as that of Ni–۷ wt % P, and the difference in thermal expansion between the substrate and the coating was responsible for the cracks in the coating. Diffusion of the molten salt through these cracks expanded and reached the intersection of the coating and the substrate. The results of the XRD showed the formation of NiSO4, NiO, and Cu on the coating surface after the hot corrosion test.

Keywords: electroless, Ni–P, molten salt, hot corrosion, hot mount

DOI: 10.3103/S1068375515040055

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The Effect of B4C Nanoparticles on the Corrosion and Tribological Behavior of Electroless Ni–B–B 4C Composite Coatings

M. Rezagholizadeh, M. Ghaderi, A. Heidary, and S. M. Monirvaghefi

Abstract—In this study, the electroless method was successfully used to deposit composite coatings containing B4C nanoparticles on Ck45 carbon steel. The characteristics of coatings were investigated with the X-ray diffraction (XRD) and scanning electron microscopy (SEM). The hardness of coatings was measured by Vickers microhardness test with a load of 1 N. The hardness of the composite coating of Ni–B–B4C was about 870 Vickers, which increased to 1350 Vickers after heat treatment at 400°C for 1 hour, which was much more than for Ni–B coating and Ck45 steel. The wear test was carried out using the pinondisk test technique. The results indicated an improvement in the wear resistance of Ni–B–B4C composite coatings com
pared to that of Ni–B and Ck45. The results obtained from the Tafel polarization test indicated an increasein the corrosion resistance of Ni–B–B
۴C composite coatings compared to that of Ni–B coatings and Ck45 steel.

Keywords: nanoB4C, electroless deposition, composite coating, tribological behavior, corrosion
DOI: 10.3103/S1068375515010135

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Investigation of Solvothermal Synthesis and Formation Mechanism of Fe2O3/C Microspheres

H. Safarzadeh, R. EbrahimiKahrizsangi, M. Ghaderi*, and A. SaffarTalouri

Abstract—In this research we report a onestep method to fabricate Fe2O3/C microspheres by using the rolling scales oxides via the solvothermal approach. The thermal gravimetric Analysis (TGA) experiment was carried out in order to determine the amount of carbon in the synthesized samples. Only Fe2O3 peaks could be observed from Xray diffractometry patterns; the carbon in the composite was amorphous. The content of the carbon in the composite was calculated to be about 72 wt %. After annealing at 800°C, scanning electron microscopy images showed that the surface of microspheres was rather smooth and their diameters were in the range of 1–۳٫۵ μm. The investigation of Fe2O3/C microspheres formation mechanism revealed that Fe2O3 nanoparticles are homogeneously distributed in the carbon matrix

Keywords: microsphere, solvothermal approach, Fe2O3, carbon, electrode
DOI: 10.3103/S1068375515040122

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