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1.
Shiyan Zhang Qing Li Xiaokui Yang Xiankang Zhong Yan Dai Fei Luo 《Materials Characterization》2010,61(3):269-276
In this paper, a protective multilayer coating, with electroless Ni coating as bottom layer and electrodeposited Ni–TiO2 composite coating as top layer, was successfully prepared on AZ91D magnesium alloy by a combination of electroless and electrodeposition techniques. Scanning electron microscopy and X-ray diffraction were employed to investigate the surface, cross-section morphologies and phase structure of coatings, respectively. The electrochemical corrosion behaviors of coatings in 3.5 wt.% NaCl solutions were evaluated by electrochemical impedance spectroscopy, open circuit potential and potentiodynamic polarization techniques. The results showed that the corrosion process of Ni–TiO2 composite coating was mainly composed of three stages in the long-term immersion test in the aggressive media, and could afford better corrosion and mechanical protection for the AZ91D magnesium alloy compared with single electroless Ni coating. The micro-hardness of the Ni–TiO2 composite coating improved more than 5 times than that of the AZ91D magnesium alloy. 相似文献
2.
Wear and corrosion protection using Cr and CrN (PVD coating on Al and Mg) Investigations of the wear behaviour of uncoated Magnesium and Aluminium alloys (AZ 91hp, AlSi 7Mg) are showing very high wear rates of these materials. To improve the wear behaviour both materials were coated with 9 μm CrN using PVD (Physical Vapour Deposition) technology. The tribological behaviour of the coated light metals was tested afterwards by using a plate on cylinder tribometer. Looking at the results, wear is reduced enormously. The great number of defects in the coating of the magnesium alloy is showing almost no influence to the wear behaviour. The corrosion behaviour of chromium and chromium nitride coatings was tested on the magnesium alloy. Because of the defects in the coating, caused by defects like pores in the magnesium, only a short term protection of the alloy can be achieved. The corrosion behaviour of multilayer coatings is better than the behaviour of single layer coatings. 相似文献
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A. Abdel Aal 《Journal of Materials Science》2008,43(8):2947-2954
A phosphate–permanganate conversion coating was applied as the pretreatment process for AZ91D magnesium alloy substrate. Zn–Ni
alloys were electrodeposited onto the treated AZ91D magnesium alloy from sulfate bath. The morphology and phase composition
of the coatings were determined with X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). The results reveal that
the conversion rate depends on pH of solution and treatment time. Salt spray and the electrochemical polarization testing
were applied to evaluate the corrosion performance of phosphate–permanganate and Zn–Ni coated alloys. It was found that Ni
content in deposit is a function of current density and bath composition. Zn–13 wt.% Ni coating provides very good corrosion
protective function to inner AZ91D magnesium alloy. Phosphate–permanganate treatment enhances the corrosion resistance of
Zn–Ni coatings. 相似文献
4.
Influence of phytic acid concentration on performance of phytic acid conversion coatings on the AZ91D magnesium alloy 总被引:3,自引:0,他引:3
Xiufang Cui Ying Li Qingfen Li Guo Jin Minghui Ding Fuhui Wang 《Materials Chemistry and Physics》2008,111(2-3):503-507
In this study, the phytic acid conversion coating, a new environmentally friendly chemical protective coating for magnesium alloys, was prepared. The influences of phytic acid concentration on the formation process, microstructure, chemical state and corrosion resistance of the conversion coatings on AZ91D magnesium alloy were investigated by means of weight gain measurement, field-emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, potentiodynamic polarization method and electrochemical impedance spectroscopy (EIS), respectively. And the depth profile of all elements in the optimal conversion coatings was analyzed by auger electron spectroscopy (AES).The results show that the growth, microstructure, chemical state and corrosion resistance of the conversion coatings are all obviously affected by the phytic acid concentration. The concentration of 5 g l−1 corresponds to the maximum weight gain. The main elements of the coating are Mg, Al, O, P, and C, which are distributed gradually in depth. The functional groups of conversion coatings formed in higher concentration phytic acid solution are closer to the constituent of phytic acid than those formed in lower concentration phytic acid solution. The coatings formed in 1–5 g l−1 are integrated and uniform. However, those formed in 20–50 g l−1 have some micro-cracks on the α phase. The coating formed in 5 g l−1 has the best corrosion resistance, whose open circuit current density decreases about six orders than that of the untreated sample, although the coatings deposited in 1–20 g l−1 can all improve the corrosion resistance of AZ91D. 相似文献
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《Materials Characterization》2007,58(10):917-921
In this study, AlN/TiN was coated on magnesium alloys using physical vapour deposition (PVD) technique of DC magnetron sputtering, and the influence of the coating on the wear behaviour of the alloys was examined. A physical vapour deposition system for coating processes, a reciprocating wear system for wear tests, a universal hardness equipment for hardness measurement, a X-ray diffractometer (XRD) for compositional analysis of the coating, and a scanning electron microscopy (SEM) for surface examinations were used. It was determined that the wear resistance of the magnesium alloys can be increased by PVD coatings. However, small structural defects which could arise from the coating process or substrate were observed in the coating layers. 相似文献
7.
M. Bobby Kannan O. Wallipa 《Materials science & engineering. C, Materials for biological applications》2013,33(2):675-679
In this study, a magnesium alloy (AZ91) was coated with calcium phosphate using potentiostatic pulse-potential and constant-potential methods and the in vitro corrosion behaviour of the coated samples was compared with the bare metal. In vitro corrosion studies were carried out using electrochemical impedance spectroscopy and potentiodynamic polarization in simulated body fluid (SBF) at 37 °C. Calcium phosphate coatings enhanced the corrosion resistance of the alloy, however, the pulse-potential coating performed better than the constant-potential coating. The pulse-potential coating exhibited ~ 3 times higher polarization resistance than that of the constant-potential coating. The corrosion current density obtained from the potentiodynamic polarization curves was significantly less (~ 60%) for the pulse-deposition coating as compared to the constant-potential coating. Post-corrosion analysis revealed only slight corrosion on the pulse-potential coating, whereas the constant-potential coating exhibited a large number of corrosion particles attached to the coating. The better in vitro corrosion performance of the pulse-potential coating can be attributed to the closely packed calcium phosphate particles. 相似文献
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To improve the wear and corrosion resistance of AZ91D magnesium alloy, Zr-based coating made of Zr powder was fabricated on AZ91D magnesium alloy by laser cladding. The microstructure of the coating was characterized by XRD, SEM and TEM techniques. The wear resistance of the coating was evaluated under dry sliding wear test condition at room temperature. The corrosion resistance of the coating was tested in simulated body fluid. The results show that the coating mainly consists of Zr, zirconium oxides and Zr aluminides. The coating exhibits excellent wear resistance due to the high microhardness of the coating. The main wear mechanism of the coating and the AZ91D sample are different, the former is abrasive wear and the latter is adhesive wear. The coating compared to AZ91D magnesium alloy exhibits good corrosion resistance because of the good corrosion resistance of Zr, zirconium oxides and Zr aluminides in the coating. 相似文献
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H. Hoche H. Scheerer E. Broszeit C. Berger S. Flege H. M. Ortner 《Materialwissenschaft und Werkstofftechnik》2001,32(3):259-265
PVD‐CrN coated magnesium alloy AZ91hp and steel 100Cr6 – Investigation on the influence of the substrate material on coating properties PVD‐chromium‐nitride coated samples of substrates of the magnesium alloy AZ91hp and the roller and ball bearing steel 100Cr6 were investigated regarding structure, mechanical characteristics, adhesion and internal stresses. For the coatings the parameters layer thickness and substrate BIAS voltage were varied. Both substrate materials were coated in one lad. Results of the x‐ray analysis of the internal stresses show significant differences between the coated magnesium and the coated steel substrates. In the case of the variation of the substrate BIAS voltage, for the coated steel a dependency of the internal stresses to coating parameters could be obtained. For the coated magnesium no dependency was recognizable. The coating structure was examined with scanning electron microscopy. Element depth profiles of the coated samples were performed with SIMS. 相似文献
11.
In the present work, the effect of applying ternary Ni–P–B4C composite coating from an electroless plating bath containing sulfate nickel, sodium hypophosphate and suspended B4C particles, on the corrosion and wear resistance of an AZ91D, high aluminum cast magnesium alloy, was investigated. Regarding low corrosion resistance of magnesium alloys, chromium oxide plus HF (Hydro Fluoric Acid) pretreatment was applied to prepare the substrate for coating treatment in electroless bath. The pH value and temperature of the electroless bath were 9 and 82 °C, respectively. The coating was characterized for its micro structure, morphology, microhardness, wear and corrosion resistance. SEM (Scanning Electron Microscope) observation showed dense and coarse nodules in the ternary composite coating and the cross section of Ni–P–B4C coating offered presence of well dispersed B4C particles in the coating. The hardness of the Ni–P–B4C composite coatings was around 1200 MPa, more than what can be obtained for Ni–P coatings (about 700 MPa). The wear test which was carried out by using pin on disc method, showed that ternary Ni–P–B4C composite coating had a good wear resistance and more superior than Ni-P coating. The polarization test results for ternary Ni–P–B4C composite coating exhibited good corrosion resistance properties in protecting the AZ91D magnesium alloy, but not better than Ni–P coating. 相似文献
12.
电解液组成对AZ91D镁合金微弧氧化的影响 总被引:12,自引:0,他引:12
在含有NaAlO2、KF的电解质溶液中,采用恒电流方式对AZ91D镁合金进行微弧氧化获得陶瓷膜.研究了电解液组分及浓度对陶瓷氧化膜厚度及表面形貌的影响,同时,采用动电位极化曲线及电化学交流阻抗评价了陶瓷氧化膜的耐蚀性.研究发现:NaAlO2单独存在时即可产生火花放电现象,但得到的氧化膜较薄;氟化钾的加入可以显著增加氧化膜厚度,膜厚的增长速度与氟化钾的加入量呈线性关系.SEM表面形貌分析表明:电解质浓度较低时产生的氧化膜宏观上较粗糙、微观上颗粒结合紧密;高浓度时得到的氧化膜宏观上细致光滑,微观上存在明显的孔洞和放电隧道,呈熔融状态结合在一起.动电位极化曲线及电化学交流阻抗的测试一致表明,经微弧氧化处理后的镁合金耐蚀性显著提高. 相似文献
13.
Guosong Wu 《Materials Letters》2007,61(18):3815-3817
Multi-magnetron sputtering was applied to prepare aluminum coating and aluminum/titanium multilayer coating on AZ31 magnesium alloy. FESEM, AFM and XRD were used to investigate the morphology and phase structure of these obtained coatings. Aluminum coating presented a (111) preferred texture and this texture was strongly strengthened with the Ti(002) plane as template in Al/Ti multilayer coating. The top surface of Al/Ti-coated sample took on a round roof-like morphology compared to the pyramid-like morphology of Al-coated sample. The result of polarization tests showed that both Al coating and Al/Ti multilayer coating could improve the corrosion resistance of AZ31 magnesium alloy in 3.5 wt.% NaCl solution. 相似文献
14.
为了进一步提高镁合金表面Ni-Mo-P镀层的耐蚀性,采用0M、XRD和浸泡试验等方法,研究了退火处理对AZ31镁合金表面Ni-Mo-P镀层组织与腐蚀性能的影响。结果表明:AZ31镁合金阳极氧化-化学镀Ni-Mo-P镀层表面为“胞状”组织,随着退火温度的升高或退火时间的延长,AZ31镁合金阳极氧化-化学镀Ni-Mo-P镀层的胞状组织逐渐细化,但镀层厚度降低,同时,非晶态Ni-Mo-P镀层组织逐渐向晶态转变,350℃退火1.0h具有较高的非晶化程度,退火处理后的Ni-Mo-P镀层由Mg、MgO、Mg2SiO4、Ni和Ni3P组成;退火使AZ31镁合金阳极氧化-化学镀Ni-Mo-P镀层耐蚀性降低,350℃退火1.0 h镀层具有相对较好的耐蚀性,这与镀层的厚度和非晶化程度有关。 相似文献
15.
H. Hoche H. Scheerer R. Fritsche A. Thißen S. Flege E. Broszeit C. Berger H. M. Ortner W. Jaegermann 《Materialwissenschaft und Werkstofftechnik》2002,33(3):132-141
Investigating the Influence of the Sputter Etching Process on the Properties of PVD‐CrN Coatings on Magnesium Die Cast Alloy AZ91hp A common method prior to the PVD deposition is the sputter etching process of the substrate itself to clean the surface from adhesion products and to improve the coating adhesion. This report deals with the sputter etching of magnesium die cast alloy AZ91hp to investigate the influences on the coating‐substrate interface, the surface properties and the mechanical properties of PVD‐CrN hard coatings. The coating‐substrate interface of the Cr‐AZ91 coating systems was investigated with XPS and SIMS. Surface studies were carried out by high resolution electron microscopy and AFM. The characterization of the mechanical properties of the CrN‐AZ91 compound systems includes thickness, coating hardness and hardness depth profiles, coating adhesion, structure and residual stresses. Some properties show a strong dependency of the etching time, especially the mechanical properties and the coating roughness. Increasing etching times lead to an improvement of the coating quality. 相似文献
16.
Qiang Wang Yaohui Liu Shijie Fang Yulai Song Dawei Zhang Lina Zhang Chunfang Li 《Materials Characterization》2010,61(6):674-682
The influence of yttrium on the corrosion residual strength of an AZ91D magnesium alloy was investigated detailedly. Scanning electron microscope was employed to analyze the microstructure and the fractography of the studied alloys. The microstructure of AZ91D magnesium alloy is remarkably refined due to the addition of yttrium. The electrochemical potentiodynamic polarization curve of the studied alloy was performed with a CHI 660b electrochemical station in the three-electrode system. The result reveals that yttrium significantly promotes the overall corrosion resistance of AZ91D magnesium alloy by suppressing the cathodic reaction in corrosion process. However, the nucleation and propagation of corrosion pits on the surface of the 1.0 wt.% Y modified AZ91D magnesium alloy indicate that pitting corrosion still emerges after the addition of yttrium. Furthermore, stress concentration caused by corrosion pits should be responsible for the drop of corrosion residual strength although the addition of yttrium remarkably weakens the effect of stress concentration at the tip of corrosion pits in loading process. 相似文献
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YingLI FuhuiWANG HongweiHUO 《材料科学技术学报》2003,19(5):459-462
Magnesium coatings were fabricated on stainless steel substrates (1Cr11Ni2W2MoV) by a plane magnetron sputtering technique. The argon pressure and the substrate condition (including temperature and the substrate was rotated or fixed) were varied in order to evaluate the influence of the parameters on the crystal orientation and morphology of the coating. The corrosion behavior of the coatings in 1 wt pct NaCl solution was studied by electrochemical methods.The results showed that all coatings exhibited preferred orientation (002) as the argon pressure increased from 0.2 to 0.4 Pa. The morphologies of the coatings varied with the argon pressure and with whether the substrate was rotated or fixed. The open circuit potential of the coatings was more positive than that of cast AZ91D magnesium alloy.However, the immersion test in 1 wt pct NaCI solution showed that the corrosion rates of the coatings were higher than that of cast AZ91D magnesium alloy. 相似文献
20.
Tingfang Chen Wenbin Xue Yongliang Li Xiaolong Liu Jiancheng Du 《Materials Chemistry and Physics》2014
A protective ceramic coating of about 50 μm thick on a friction stir welded (FSW) joint of AZ31B magnesium alloy was prepared by plasma electrolytic oxidation (PEO) in silicate electrolyte. Electrochemical corrosion behavior of uncoated and coated FSW joints was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The equivalent circuits of EIS plots for uncoated and coated FSW magnesium alloy were suggested. The corrosion resistance of FSW magnesium alloy depended on microstructure of the FSW joint. The heat-affected zone with severe grain growth was more susceptible to corrosion than the stir zone and base metal. The PEO coating consisted of a porous outer layer and a dense inner layer. The inner layer of PEO coating played a key role on corrosion protection of the FSW joint of magnesium alloy. Meanwhile, corrosion potential, corrosion current density and impedance at different zones of coated FSW joint were almost the same. The PEO surface treatment significantly improved the corrosion resistance of FSW joints of AZ31B magnesium alloy. 相似文献