Effect of stirring on microstructure and properties of trivalent chromium coatings on fine, thin, and long hooked-groove part
WANG Fashun;ZHU Shigen;GONG Wendi;DONG Weiwei;BAI Yunfeng;LUO Yilan;[Objective] Fine, thin, and long hooked-groove parts often encounter issues such as burnt coatings at fine hooks and skip-plating at inner wall of narrow-deep-long grooves during trivalent chromium electroplating, primarily due to uneven current density and solution mass transfer. [Method] Trivalent chromium electroplating was performed on fine, thin, and long hooked-groove parts in both stationary and agitated bath(stirring rate of 200, 400, or 600 r/min). The effects of agitation on the microstructure, adhesion, microhardness, and wear resistance of Cr coatings at different positions of the parts were studied by scanning electron microscopy(SEM), adhesion test, microhardness measurement, and friction-wear test. [Result] Appropriate agitation during electroplating significantly improved the distribution uniformity and microstructure of coatings across various part regions, consequently enhancing coating properties such as adhesion, microhardness, and wear resistance. [Conclusion] Bath stirring effectively resolved the problems of hook burning and groove skip-plating. A stirring rate of 400 r/min yielded chromium coatings that were uniform, compact, and smooth across all part areas, exhibiting the highest microhardness and the best wear resistance.
Preparation and properties of a highly corrosion-resistant gold coating
GUO Chongwu;LI Xiaohua;WANG Xiaojun;Guangdong Polytechnic Normal University;[Objective] A novel gold plating process for preparing highly corrosion-resistant coating was developed, aiming to address the critical issues of cyanide-based gold plating on zinc alloy die castings, such as severe environmental pollution, and insufficient overall corrosion resistance. [Method] A multi-layered coating was prepared on zinc alloy substrate through a sequential process involving cyanide-free copper–zinc alloy plating, pyrophosphate copper plating, acid copper plating, bright nickel plating, nickel–tin alloy plating, and strike gold plating on the zinc alloy die casting. [Result] By applying the strike gold plating over the high corrosion-resistant nickel–tin alloy layer, excellent interlayer adhesion was achieved. The obtained coating passed the thermal shock test without blistering or peeling, and withstood 240-hour neutral salt spray test without any signs of corrosion. [Conclusion] The newly developed process is environmentally friendly, can prepared coatings with superior performance at a relatively lower cost, demonstrating promising application prospects and significant market potential.
Effect of ion vapor deposition of aluminum on surface integrity and fatigue property of AISI 4340 steel
JIA Tianyi;BAO Qipeng;MAI Jiaqi;QIN Rui;YU Bo;ZHAN Zhongwei;AECC Beijing Institute of Aeronautical Materials;[Objective] The effect of ion vapor deposition(IVD) of aluminum on the surface integrity and fatigue property of AISI 4340 steel needs to be studied. [Method] Using tempered AISI 4340 steel as the substrate, aluminum coatings with thicknesses of 10 μm and 16 μm were deposited on the specimen surfaces via ion vapor deposition followed by sandblasting pretreatment. The microstructure, surface roughness, and residual stress distribution of specimens at different processing stages were compared by scanning electron microscopy(SEM), laser confocal microscopy(LCM), and X-ray residual stress analysis. The influencing mechanism of aluminum IVD on the fatigue property of AISI 4340 steel was analyzed. [Result] The surface roughness of substrate was significantly increased and numerous micro-pits were formed after sandblasting, which induced stress concentration under load, leading to a substantial decrease in fatigue performance(a reduction of 12.2%). A shallow residual compressive stress of approximately 200 MPa was formed on the surface. However, due to the plastic buffering effect of the aluminum layer, this stress did not affect the substrate surface. [Conclusion] The increased surface roughness and defect formation caused by sandblasting are the primary reasons for the degradation in fatigue performance, while the ion-plated aluminum coating has a relatively limited impact on AISI 4340 steel's fatigue properties.
Effect of hydrogen peroxide on corrosion resistance of electrolessly plated nickel–phosphorus alloy coating
XU Zhousheng;HU Guanghui;PAN Zhanchang;HE Nian;[Objective] The effects of hydrogen peroxide on the microstructure and corrosion resistance of electroless plated Ni–P alloy coatings were studied to improve their corrosion resistance. [Method] Different volume fractions(0-1.0 mL/L) of hydrogen peroxide were added to a basic electroless nickel plating bath. The deposition rate was analyzed by thickness measurement. The surface morphology, elemental composition, and phase structure of Ni–P alloy coatings were characterized using metallographic microscopy, scanning electron microscopy(SEM), energy-dispersive spectroscopy(EDS), and X-ray diffraction(XRD). The corrosion resistance of the coatings was evaluated through nitric acid spot test and electrochemical measurements. [Result] The addition of hydrogen peroxide reduced the deposition rate of electroless nickel plating and promoted a denser arrangement of cellular particles on the coating surface. The resulting Ni–P alloy coatings exhibited a phosphorus content in the range of 6%-9%(mass fraction) and an amorphous structure. As the volume fraction of hydrogen peroxide increased, the corrosion resistance of the coatings improved initially and then decreased, showing the best corrosion resistance at 0.6 mL/L. [Conclusion] The addition of an appropriate amount of hydrogen peroxide to the plating bath can effectively enhance the corrosion resistance of Ni–P alloy coatings, which is closely related to the coating density and phosphorus content.
Research progress in electroplating baths for nickel-and nickel alloy-based electroplated diamond wires
ZHANG Rong;ZHU Dongao;FAN Pengpeng;XU Lixian;CHEN Jialu;WU Jiqing;WANG Yicheng;JIANG Wei;LI Huaming;XU Hui;[Objective] Electroplated diamond wire serves as a critical tool in precision machining fields such as silicon wafer cutting, with its performance strongly correlated to how electroplating bath components affect diamond adhesion and coating uniformity. [Method] The research progress of three electroplating bath including chloride, sulfate, and sulfamate, for nickel and nickel alloy based electroplated diamond wires was reviewed. [Result] Optimizing the electroplating bath composition can facilitate directional attachment of diamond particles while improving coating uniformity and densification, thereby significantly enhancing the cutting efficiency and precision of diamond wires. [Conclusion] Future research should focus on developing environmentally friendly plating baths, decreasing cost, and improving electroplating efficiency to meet the demands of high-performance precision machining.
Solder joint reliability of ABF substrates with different printing solders after uHAST and HTST aging
LIU Gang;ZHANG Wenjian;CHEN Jia;ZHU Guanjun;YANG Zhiqin;[Objective] The intermetallic compound (IMC) growth behavior and soldering performance evolution of ABF substrates with different printing solders after ultra-high accelerated humidity stress testing (uHAST) and high-temperature stress testing (HTST) were studied. [Method] The solder joints were observed and analyzed using scanning electron microscopy (SEM)， energy dispersive spectroscopy (EDS)， and a multi-function push-pull tester. [Results] After uHAST and HTST， the cross-section of the IMC layer in the electrolessly tin-plated specimens exhibited a scallop-like morphology， with a pebble-like appearance in top-view. In contrast， the electrolessly nickel/palladium/gold-plated specimens showed a dendritic IMC cross-section and a polyhedral top-view morphology. For the specimens treated by the same process， the IMC layer thickness with SC07 solder was consistently greater than that with SAC305 solder throughout the aging testing. For the specimens with the same solder， the IMC layer thickness in electrolessly tin-plated specimens was always greater than that in ENEPIG specimens. No Kirkendall voids were observed in all specimens. During uHAST， the solder joint strength of electrolessly tin-plated specimens decreased， while it increased during HTST. For the electrolessly nickel/palladium/gold-plated specimens， the solder joint strength initially increased and then decreased during HTST. [Conclusion] This study provides theoretical reference for ABF substrate design.
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Preparation and thermal conduction properties of copper/graphite flake composites with high thermal conductivity and low thermal expansion
ZHANG Lili;WANG Jian;ZHANG Ning;ZHAO Yongqiang;[Objective] To address the poor thermal conductivity of traditional copper/carbon composites caused by weak interfacial bonding and enhance their application potential in heat dissipation for high-power electronic devices， a copper/graphite flake (Cu/GF) composite with both high thermal conductivity and low thermal expansion characteristics needs to be developed. [Method] Cu/graphite flake composites were prepared by copper electroplating prior to spark plasma sintering (SPS). Graphite flakes were firstly subjected to surface oxidation to introduce oxygen-containing functional groups， followed by palladium activation. Subsequently， electroplating copper was conduted to obtain Cu/GF composite powders with different Cu mass fractions. Finally， spark plasma sintering was carried out to achieve metallurgical bonding at the interface between Cu layer and graphite flakes. The effect of Cu mass fraction and graphite flake orientation on the thermal conductivity of Cu/GF composite was studied. The three-dimensional microstructure and thermal conduction performance of Cu/GF composites were simulated and analyzed. [Result] The Cu/GF composite with 40wt% Cu exhibited the optimal thermal conductivity， as shown by an axial thermal conductivity as high as 692 W/(m·K) and a thermal expansion coefficient as low as 4.12 × 10-6 K-1. Microstructural characterization revealed the formation of a three-dimensional interpenetrating network structure in which the copper phase continuously coated the graphite flakes， effectively enhancing the interfacial bonding strength and heat transport efficiency. Numerical simulation results were generally consistent with experimental findings， indicating that the orientation of graphite flakes significantly influences the thermal conductivity of the composite. [Conclusion] Through interface optimization and structural design， the Cu/graphite flake composite achieves ultra-high thermal conductivity and ultra-low thermal expansion， providing a new generation of thermal management solutions for advanced fields such as power battery modules and high-density integrated circuits.
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Hexagonal boron nitride/silica-filled epoxy coating for concrete protection: fabrication and performance evaluation
SHI Wangfang;ZHANG Yongsheng;[Objective] Carbonation and chloride ion corrosion will seriously affect the durability and service life of concrete. [Method] The surface modification of nano-SiO2 and hexagonal boron nitride (HBN) was realized by silane coupling agent (KH550) and dopamine hydrochloride. The nano-SiO2 was grafted onto the surface of HBN by condensation reaction to prepare dopamine hydrochloride-HBN/KH550-SiO2 (DA-HBN/KH-SiO2) inorganic filler. The phase chemical composition， elemental composition and microstructure were characterized by XRD， FT-IR， XPS， SEM and TEM. Epoxy resin (EP) was used as film-forming matrix， nano-SiO2， HBN and DA-HBN/KH-SiO2 were used as inorganic fillers to construct protective coatings on the surface of concrete to improve the durability of concrete. The thermal stability， bonding strength， waterproof performance， chloride ion penetration resistance and carbonation resistance of epoxy coatings with different inorganic fillers were studied. [Result] The three kinds of inorganic filler epoxy protective coatings can effectively improve the carbonation resistance and chloride ion penetration resistance of concrete. DA-HBN/KH-SiO2/EP protective coating can more effectively improve the durability of concrete. Compared with EP protective coating， the chloride ion content and 28 d carbonation depth of concrete at the depth of 0～5 mm decreased by 36.70% and 64.79%， respectively. At the same time， DA-HBN/KH-SiO2/EP protective coating has high bonding strength with concrete， which can effectively prevent the shedding of protective coating. The good dispersion and physical barrier of DA-HBN/KH-SiO2 inorganic filler in epoxy coating improved the waterproof performance and thermal stability of the coating. [Conclusion] The incorporation of DA-HBN/KH-SiO2 inorganic fillers into epoxy coating can effectively improve the carbonation resistance and chloride ion penetration resistance of concrete.
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Corrosion resistance and biocompatibility of magnetron-sputtered Mg–Si composite film on AZ31 magnesium alloy surfaces
ZHANG Shikun;HOU Shusen;LI Wenxing;ZHANG Jinghao;[Objective] Medical magnesium alloys show great potential in bone implant materials due to their density close to that of human bone and excellent biocompatibility. However， their excessively rapid degradation in physiological environments can lead to premature loss of mechanical integrity， localized pH increase， and hydrogen gas accumulation， which severely limit their clinical application. This study aims to enhance the corrosion resistance of magnesium alloys while maintaining good biocompatibility through surface modification. [Methods] A Mg–Si composite film was prepared on the surface of AZ31 magnesium alloy using magnetron co-sputtering. Orthogonal experiments were carried out to optimize the sputtering parameters， including pressure， metal target power， and sputtering time. The surface morphology， roughness， and corrosion resistance of Mg–Si composite film were characterized by scanning electron microscopy (SEM)， white light interferometry， electrochemical measurement， and simulated body fluid (SBF) immersion test. In vitro cytotoxicity and biocompatibility were evaluated via CCK-8 assay and cell fluorescence staining. [Results] The optimal magnetron sputtering parameters were determined as follows: pressure 0.30 Pa， Mg target power 40 W， Si target power 120 W， and sputtering time 1 h. The Mg–Si composite film obtained under the optimized conditions exhibited a uniform and compact surface with a low surface roughness (Ra) of 30.5 nm. Electrochemical measurements revealed that the film reduced the corrosion current density of the substrate by nearly two orders of magnitude， and the anodic branch displayed passivation characteristics， indicating significantly improved corrosion resistance. In vitro cell experiments confirmed that the Mg–Si composite film promoted higher cell proliferation rates and better cell morphology compared to the untreated AZ31 magnesium alloy， demonstrating excellent biocompatibility. [Conclusion] A Mg–Si composite film with excellent corrosion resistance and biocompatibility can be successfully prepared on surface of AZ31 magnesium alloy by magnetron co-sputtering. This study provides an effective surface modification strategy to address the issue of excessively rapid degradation of medical magnesium alloys.
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Properties of an eco-friendly hydroxyethylidene diphosphonic acid-based chemical conversion coating on TC4 titanium alloy
YAN Honglin;ZUO Hanyang;WU Tong;XU Zhenghong;LIU Wenli;YANG Shengjie;LU Jianhong;[Objective] An environmentally friendly chemical conversion coating based on hydroxyethylidene diphosphonic acid (HEDP) was studied， aiming to enhance the adhesion of paint on TC4 titanium alloy and improve its resistance to galvanic corrosion when coupled with other metals. [Method] An organophosphonate coating was formed on the TC4 titanium alloy surface by chemical conversion in a solution with varying concentrations of HEDP as the main film-forming agent at 70 ℃ for 5 min. The microstructure， phase composition， surface roughness， chemical composition， adhesion， compactness， and galvanic corrosion resistance of the coating were analyzed by scanning electron microscopy (SEM)， X-ray diffraction (XRD)， energy-dispersive spectroscopy (EDS)， 3D surface profilometry， Fourier-transform infrared spectroscopy (FT-IR)， and an electrochemical workstation. [Result] When the HEDP mass concentration in conversion solution was 300 g/L， the resulting coating was smooth and compact， with a film resistance of 8.70 × 103 Ω·cm2 and a low surface roughness (Sa = 1 564.89 nm). The adhesion between the conversion coating and the polyurethane (PU) coating reached 20.67 MPa， representing a 190% improvement compared to the untreated TC4 titanium alloy substrate. The enhancement in adhesion maybe attributed to the synergistic effect of extensive hydrogen bonding sites and mechanical interlocking provided by the micro-cracked structure of conversion coating. The coating primarily consisted of Ti–HEDP， TiO2， TiOF2， and TiF3. Under these conditions， the galvanic current density between TC4 titanium alloy and 304 stainless steel was as low as 0.011 μA/cm2， corresponding to a Grade A galvanic corrosion rating， indicating negligible corrosion. [Conclusion] The HEDP-based conversion coating significantly improves both the adhesion of
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Development and application of thermal spraying technology
WANG Yong-bing, LIU Xiang, QI Wen-jun LI Zhi-guo: College of Mechanical Engineering Xinjiang University, Urumchi 830008, ChinaThe technics characteristic of thermal spraying technology was introduced. Advantages and disadvantages of five kinds of thermal spraying technologies including high velocity oxygen fuel flame spraying process, hypersonic plasma spray process, laser spray process, reactive spray process and cold gas dynamic spray process were analyzed. Application status of thermal spray process was summarized. The prospect of new technics and materials application to thermal spraying technology was discussed.
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Characteristics, applications and research direction of micro-arc oxidation technology
ZHONG Tao-sheng~(1,2), JIANG Bai-ling~2, LI Jun-ming~2 (1. School of Applied Science, Jiangxi University of Technology, Ganzhou 341000, China; 2. Institute of Material Science and Engineering, Xi'an Industry University, Xi'an 710048, China)Research status and development of nano-material electrodeposition
DENG Shu hao, GONG Zhu qing, CHEN Wen gu (Dept. of Metallurgical Science and Engineering, Zhongnan Univ., Changsha 410083, China)Preparation of nano-metal nano alloy and nano complex material by electrodeposition was reviewed, as well as structure characteristics, excellent properties of the deposit and its application forecast.
Development status of pulse current plating
XIANG Guo-pu (Dept. of Appl. Chemistry., Tianjin Univ., Tianjin 300072, China)Application status of pulse current plating in chromium, copper, nickel and its alloy, gold and its alloy, silver and its alloy, palladium and its alloy electroplating were summarized. Pulse reverse plating, composite pulse plating and amorphous alloy pulse plating were also described.
Treatment of hexavalent chromium-containing electroplating wastewater by barium salt precipitation
LI Hang-bin;QIAN Bo;HUANG Cong-cong;CHEN Xin-cai;ZHANG Shi-xin;LIU Xiang-hu;Hexavalent chromium-containing electroplating wastewater was treated by barium salt precipitation. The effects of pH pre-adjustment of wastewater, cyanide decomposition method, and addition of Cr(VI) precipitator on the removal of hexavalent chromium, total chromium, copper, and nickel were studied. The influence of the dosage of sulfuric acid on the recovery of hexavalent chromium was examined. The optimal process parameters for treatment of hexavalent chromium-containing electroplating wastewater by barium salt precipitation are as follows: pre-adjusted pH 8,barium salt dosage 2.5 times of the theoretical value, cyanide decomposition with hydrogen peroxide, and final pH 10 adjusted with liquid caustic soda. After treating under the optimal process conditions, the total chromium content and nickel content in effluent is 0.4 mg/L and 0.3 mg/L, and no copper is detected, all of which are below the emission limits of Table 2 in the GB 21900–2008 standard. The recovery of hexavalent chromium in barium chromate sediment reaches 65% by solid–solid transformation using sulfuric acid. The costs for reagent and treatment of hazardous solid waste by barium salt precipitation are higher than those of traditional chemical reduction. Barium salt precipitation is suitable for professional chrome plating factories and plating industrial parks where chromium wastewater is strictly discharged and collected individually.
Development and application of thermal spraying technology
WANG Yong-bing, LIU Xiang, QI Wen-jun LI Zhi-guo: College of Mechanical Engineering Xinjiang University, Urumchi 830008, ChinaThe technics characteristic of thermal spraying technology was introduced. Advantages and disadvantages of five kinds of thermal spraying technologies including high velocity oxygen fuel flame spraying process, hypersonic plasma spray process, laser spray process, reactive spray process and cold gas dynamic spray process were analyzed. Application status of thermal spray process was summarized. The prospect of new technics and materials application to thermal spraying technology was discussed.
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Current status of research on waterborne polyurethane coatings
ZENG Xian-guang;GONG Min;LIU Chao-hui;ZHANG Ying-jun;ZHANG Jing-yu;The film formation mechanism of waterborne polyurethane coating was briefly described. The current status of the research on preparation and modification of one-and two-component waterborne polyurethane coatings was introduced. The development trends of waterborne polyurethane coatings were pointed out.
Principle, application and research prospect of electroless copper plating
LI Neng-bin, LUO Wei-yin, LIU Jun-quan, XU Jin-lai College of Industrial Equipment and Control Engineering, South China University of Technology, Guangzhou 510640, ChinaElectroless copper plating is mainly applied to the metallization for PCB and electroplating on plastics, and copper electroless deposits have good ductibility, heat conductivility and electrical conductibility. Its application scope and development were introduced. This paper also emphasizes the necessity for pretreatment of electroless copper plating and some aspects that need attention including using grease that is easy to be cleaned as antirust agent and anodic electrolytic degreasing for low-carbon steel parts, and combined acidic decreasing and alkaline decreasing, etc. Some commonly used systems and their main components of electroless copper plating were introduced. The influences of additives were discussed. The research progress of electroless copper plating for nonmetal was reported. The research keystones of copper electroless plating were presented.
Research progress of electropolishing technology
ZHANG Su-yin,DU Kai,CHEN Jia-jun,ZHAN Yong-jun,ZENG Ti-xian School of Physics and Electronic Information,West China Normal University,Nanchong 637002,ChinaThe current status,characteristic and polishing principle of electropolishing technology were introduced. The main factors affecting workpiece’s surface roughness are analyzed. The existing problems in electropolishing technology are presented.
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Current status and development trend of domestic and world coating industry(Ⅰ)——Current stastus and development trend of worldwide coating industry
ZHAO Jin-bang Shanghai Research Institute of Paint &Coatings,Shanghai 200062,ChinaAn overview was given of the current status of world coating industry.The worldwide application and research status of low contamination and pollution-free water-base coating,powder coating,non-solvent coating and high-solid coating etc,and environment contribution coating,function coating(including fluorocarbon resin coating,spraying polyuridylic elastomer,organic-inorganic composite coating,high ornamental coating,stealth coating and intelligent coating) etc,and nanomaterial applied to the coating were summarized.Development trend was presented.
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