Papers by Keyword: Electrolytic Coating

Abstract: SS440C steels show potential as highest mechanical properties compared to others martensitic stainless steels. As their properties can be altered by some particular heat treatments, this steel is suitable for a extensive ranges of applications such as bearings, gage blocks, races, valve parts and many other manufacturing important components. Unfortunately, bare SS440C substrates corrode too quickly under corrosive environments. Surface modifications that are able to reduce corrosion rates to suitable levels will allow SS440C to become a reality for much more applications [1-.

Abstract: Stainless steels, such as 440C steel are commonly used for engineering applications. The high carbon contents of this steel have significantly been attributed to low corrosion resistance properties. Surface modification such as electrolytic double layer coating with ZrO₂/Al₂O₃ was carried out to control the performance. Samples were deposited in ZrO(NO₃)₂ and Al (NO₃)₃ aqueous solution respectively. Potentiodynamic examination (Tafel Extrapolation test) was conducted to measure the corrosion resistance of coated steel. The results showed improvements in hardness properties and corrosion rate as the Al₂O₃ concentration had been increased.

Abstract: AISI 440C martensitic stainless steel is one of the most widely studied engineering materials for its tribological properties. It is capable of attaining the best mechanical properties such as high strength and hardness compared to other martensitic grades. Unfortunately, the corrosion resistance of this 440C steel is the lowest among the stainless group, which results in the precipitation of carbide phases. AISI 440C were coated using electrolytic ZrO₂ layer deposition method in ZrO(NO₃)₂ aqueous solution. In order to preserve the high mechanical properties of this steel, various heat treatment processes applied to the coated samples. After drying and annealing, the ZrO₂ coated samples were evaluated using SEM, hardness tests and corrosion tests. Some mud-crack had been indicated in all samples. However, it become more homogeneously on the sample which undergoes longer deposition time. This difference resulted in a significant improved on corrosion resistance of ZrO₂ coated sample.

Abstract: High carbon steel stainless steel such as 440C martensitic stainless steel, are commonly used for automotive components, such as ball bearings, races, gage blocks and valve. In this study, 440C steel was coated with ZrO₂ by electrolytic deposition in ZrO(NO₃)₂ aqueous solution. After annealing, the ZrO₂ coated specimens were characterized by x-ray diffraction (XRD) and scanning electron microscope (SEM). Scanning electron micrograph showed that thickness of the coated sample was approximately 0.7µm. Besides that, secondary hardening effect occurred on the annealed SS440C substrate and it might be due to the presence of secondary carbide.

Abstract: A diffusion barrier based on a NiW electrolytic coating has been developed to limit interdiffusion between a Ni-base superalloy (MCNG) and a β-NiAl bondcoating. Isothermal oxidation tests of 50h at 1100°C confirmed that W-rich layer formed with NiW coating modifies the oxidation behaviour of the bondcoat and limits interdiffusion. The diffusion barrier reduced β-NiAl  γ’-Ni3Al transformation in the bondcoating and prevented SRZ formation.

Abstract: Electrolytic coatings Ni-Mo with PPy were obtained by electrodeposition and electropolymerization from a galvanic bath containing Ni2+, MoO4 2–, ClO4 – ions and pyrrole (Py). The cyclic chronovoltamperommetric curve was used to determine the potential and current density of electrodeposition process. As the electropolymerization is anodic process while the electrodeposition is cathodic one, the electrode was working alternately as anode and cathode. The process was conducted under alternating potentiostatic or galvanostatic conditions. Comparative tests were carried out for Ni-Mo alloy. The results of structural investigation of the obtained coatings by the X-ray diffraction method show, the Ni-Mo layers are nanocrystalline solid solution of molybdenum in nickel (α phase), whereas the Ni-Mo+PPy coatings are characterized by decreased peaks coming from Ni-Mo base. Surface morphology of obtained Ni-Mo+PPy and Ni-Mo coatings was investigated by scanning microscope. It was stated, that the coatings obtained by alternating potentiostatic method exhibit multilayer character, whereas the coatings obtained under alternating galvanostatic conditions are characterized by the presence of Ni-Mo nanoagglomerates plated on polymer surface.