In order to improve the oxidation resistance of ferritic stainless steel, it is possible to deposit a protective coating on steel substrate. In this research through the usage of pack cementation method a coating of titanium was applied on the surface of AISI 430 stainless steel. Scanning Electron-Microscopy (SEM), Energy- Dispersive X-ray spectrometry (EDAX) and X-ray diffraction (XRD) were used for evaluating of coating structure. Results showed that titanium coating consisted of two layers with the total thickness of 50 micron. The titanized layer consisted of TiFe, TiFe2 and Fe2TiO5 phases. For investigating the oxidation behavior of coated and uncoated specimens, isothermal and cyclic oxidation tests were performed at 1000 C. In isothermal oxidation, the oxidation resistance of the titanium coated specimens was improved by restricting the outward penetration of chromium cation. The results of cyclic oxidation of titanium coated samples indicated that they were resistance to lamination and cracking. پرونده مقاله

Surface modification is very important in the component in industry due to wear and corrosion. In order to improve the corrosion behavior of steels, a protective coating can be deposited onto the surface. In this study Ni-TiO2 coatings were prepared on an AISI 430 stainless steel substrate by electrocodeposition process in Watt’s plating bath containing TiO2 particles. Two types of coatings was produced; without CTAB and at presence of CTAB surfactant. Isothermal oxidation behavior of uncoated and two types of coated specimens were studied up to 250 h in 800 ºC. Also cyclic oxidation was studied for 100 cycles at 800 C. Scanning electron microscope (SEM) and X-ray systems were applied in order to investigate the formed phases and structures of composite coating before and after oxidation. Results showed coated specimens at presence of CTAB surfactant had lower mass gain compared to Ni-TiO2 coated and uncoated ones after isothermal and cyclic oxidation at 800 ºC. پرونده مقاله

In order to improve the surface quality and prevention of corrosion and reduction of wear in the components like gears and bearings, they can be covered with phosphate coatings. SCM420H alloy steel was coated with manganese phosphate deposition. The microstructure and corrosion resistance of the coating was studied by change of bath pH. In order to investigate the phase analysis and coating microstructure, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used, respectively. XRD analysis from the coated surface revealed the phases of MnFe2(PO4)2(OH)2H2O, Mn(PO)3، Fe(PO)3 and (Mn,Fe)5H2(PO4)4·4H2O. Results showed the obtained coating at pH=2.1 was uniform and continuous and no crack or porosity was observed. The phosphate surface at pH=1.9 and pH=2.4 was non-uniform and included cracks. In order to investigate the corrosion resistance, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were applied on coated and uncoated specimens in 3.5% NaCl solution. The results of potentiodynamic polarization and electrochemical impedance spectroscopy tests were in agreement with microscopic images. The results of electrochemical impedance spectroscopy demonstrated that the formed manganese phosphate deposition in the bath with pH=2.1 had the highest polarization resistance (28020 Ω) compared to the formed coating in the bath at pH=1.9 (1480 Ω) and the formed coating in a bath with pH=2.4 (3155 Ω). پرونده مقاله

Chromium alloy steels are the best choice for materials used in interconnect plates used in solid oxide fuel cells. At operating temperature of solid oxide fuel cells chromium can alert to unstable Cr+6 species. These unstable species can precipitate at the cathode site, causing cathode contamination and reducing cathode efficiency. Therefore, protection of these steels at high temperatures is essential. Therefore, applying surface coatings it is one of the best effective methods to extend the life of these components against oxidation. In this study, Ni-Co-CeO2 composite coating was created by direct electrodeposition on the surface of AISI 430 ferritic stainless steel. In order to obtain proper coating, the effect of parameters of CeO2 particle concentration, current density and pH in the bath was investigated. Influence of CeO2 content (5, 10, 15 and 20 g/L), current density (15, 17, 20 and 22 mA/cm2) and pH (2.5, 3, 3.5 and 4) on the amount of CeO2 ceramic particle deposition and microstructure of coating was investigated. Scanning electron microscopy (SEM) and EDX analysis were used to determine the morphology of Ni-Co-CeO2 composite coating. The results showed that with increasing CeO2 and pH the amount of CeO2 particle deposition increased and then decreased. Also with increasing current density the deposition of CeO2 particles decreased. پرونده مقاله

یکی از بهترین روش های مؤثر برای بهبود مقاومت به سایش و سختی فولادهای زنگ نزن اعمال پوشش های سطحی است. از جمله این پوشش ها، پوشش های آلیاژی و کامپوزیتی پایه نیکل هستند. در این تحقیق، پوشش کامپوزیتی نیکل- فسفر- اکسیدتیتانیوم با استفاده از روش آبکاری الکتریکی بر روی فولاد زنگ نزن AISI 430 ایجاد شد. تأثیر pH آبکاری (3، 5/3 و 4) بر روی میکروساختار و میکروسختی و رفتار سایشی آن‌ها مورد بررسی قرار گرفت. به منظور تعیین فازهای موجود و محاسبه اندازه دانه، از روش آنالیز پرتو ایکس (XRD) استفاده شد. مشخصه یابی پوشش به کمک میکروسکوپ الکترونی روبشی (SEM) صورت پذیرفت. میکروسختی نمونه‌های بدون پوشش و پوشش‌دار توسط دستگاه ریزسختی سنج ویکرز اندازه‌گیری شد. همچنین مقاومت سایشی نمونه های بدون پوشش و پوشش داده شده با کامپوزیت نیکل- فسفر- اکسیدتیتانیوم با استفاده از آزمون پین بر روی دیسک بررسی شد. نتایج آنالیز پرتو ایکس نشان داد که افزایش pH باعث افزایش اندازه دانه ها می‌شود. همچنین نتایج آزمون میکروسختی و پین بر روی دیسک نشان داد افزایش pH موجب کاهش میکروسختی و مقاومت سایشی می‌شود. بیشترین سختی (18/618 ویکرز) مربوط به پوشش ایجاد شده در 3pH=، با غلظت gr/L 40TiO2= بود. همچنین بیشترین مقاومت به سایش و کمترین کاهش وزن ( mg15/0) نیز مربوط به همین پوشش بود. پرونده مقاله