Effect of heat treatment on the corrosion resistance and mechanical properties of selective laser melting Ti6Al4V alloy

The present work shows that the effect of several heat treatments on the corrosion resistance and mechanical properties of Ti6Al4V processed by selective laser melting (SLM). The microstructure of Ti6Al4V alloy produced by selective laser melting exhibited bulky prior β columnar grains, and a large amount of fine acicular martensites α′ were observed inside the prior β columnar grains. The acicular martensitic α′ were transformed to a mixture of α and β after heat treatment, and the grain size increases with the increase of heat-treated temperature. The results of 3.5 wt% NaCl solution electrochemical corrosion test showed that the heat-treated samples possess a higher corrosion resistance than the as-received sample. Among of them, the sample after heat-treated at 730 °C exhibited best corrosion resistance and excellent fracture strain. The sample heat treated at 1015 °C showed worst mechanical properties due to the formation of Widmanstätten structure.     

热处理对化学沉积Ni-Zn(Fe)-P合金结构和性质的影响

通过差示扫描量热(DSC)、X射线衍射(XRD)、扫描电镜(SEM)、电化学买验和失重买验研究了热处理对化学沉积Ni-Zn(Fe)-P合金结构、显微硬度、表面形貌和耐蚀性的影响。镀态镀层由非晶相和立方镍相组成(多晶态结构),在384．8℃晶化为四方Ni3P和Ni5Zn12相。镀层显微硬度随热处理温度升高而升高,相反地,500℃后随热处理温度升高而下降。在3．5％(质量分数)NaCl溶液中(pH7．0)镀态镀层的耐蚀性比经热处理过的镀层好。     

化学镀镍磷合金镀层封孔处理工艺及性能

研究了一种新型的镍磷合金镀层镀后处理工艺,即在常温下,采用化学的方法对镍磷合金镀层进行封孔处理,利用不同旋镀时间的镍磷合金镀层模拟具有不同孔隙率的镍磷合金 镀层,并采用涂膏法对封孔前、后镍磷合金镀层的孔隙率进行了测定。结果表明：经封孔处理的镍磷合金镀层的孔隙率大幅度下降,采用动电位极化技术测试了镍磷合金镀层封孔处理前、后的极化曲线,发现：经封 处理后的镍磷合金镀层,腐蚀电位正移,腐蚀电流减小,通过扫描电镜观察了封孔处理镍磷合金镀层的表面形貌,可见：经过扫描电镜观察了封孔处理后镍磷合金镀层的表面形貌,可见：经封孔处理后的镍磷合金镀层表面形成了一层保护膜,使镍磷合金镀层的孔隙得以封闭。     

Effect of heat treatment environment on the structural characteristics and microhardness of high velocity oxy-fuel sprayed tungsten carbide-cobalt coatings

In the present study, tungsten carbide-cobalt was coated on the austenitic stainless steel using high velocity oxy-fuel spraying. The as-deposited coatings were heat treated at 750 °C in air and argon gas environments. Structural characteristics of these coatings were studied using x-ray diffraction and Raman spectrum analysis. Further, the microhardness of the polished coated samples was also evaluated. The hardness of the coatings was significantly improved after heat treatment in air and argon gas environment. However, the highest hardness was observed with the coatings treated in argon gas environment. The formation of oxide phases such as tungsten trioxide and cobalt tungstate was observed after heat treatment in the air environment, whereas under the argon environment, no oxide phases were observed.     

化学沉积法制备Ni—Cu—P／CNTs复合涂层及其表征

利用化学沉积法在45^#钢基体上成功制备出Ni—Cu-P／CNTs复合涂层，为了降低碳纳米管的长径比以及提高在镀液中的分散性，对其硝酸纯化、15min球磨处理，研究了沉积液组成对Ni-Cu-P／CNTs复合涂层沉积速率的影响，通过TEM、SEM和EDS表征了复合涂层的表面形貌和微观结构。结果表明：碳纳米管的分散性良好，在复合涂层中分布均匀，复合涂层在400℃热处理后结构更加致密，EDS表明复合涂层中碳纳米管的质量分数达到3．68％。     

热处理对纳米Ni-TiN复合镀层摩擦磨损性能的影响

采用超声-电沉积的方法制备了纳米Ni-TiN复合镀层。测试了不同热处理温度下纳米Ni-TiN复合镀层的硬度和磨损量,对镀层的摩擦磨损性能进行了分析。结果表明,热处理温度在300℃时纳米Ni-TiN复合镀层的硬度和耐磨性能最佳,硬度为932.28HV,磨损量为13.5mg;复合镀层的摩擦系数随着热处理温度的升高而略有增大。     

Mechanical properties and corrosion behaviour of developed high nitrogen high manganese stainless steels

Influence of composition, specifically manganese and nitrogen content, on the microstructure associated corrosion resistance property of newly developed stainless steel has been studied. The developed steels have been characterised for their microstructure, mechanical and electrochemical properties. The results indicate that the addition of manganese and nitrogen as a substitute for nickel favours the austenite microstructure, higher yield strength (>350 MPa), tensile strength (>700 MPa), elongation and superior Charpy V-notch impact toughness properties. The results obtained from electrochemical tests such as potentiodynamic polarisation and electrochemical impedance spectroscopy of manganese stainless steel show remarkable improvement (about 4 times) in corrosion resistance exhibiting passivity behaviour like that of commercial stainless steel (316L).     

Enhancing the lifetime and corrosion resistance of gears made of carbon steel

Gears for structural machines require high fatigue strength for high performance. Generally, gears made of carbon steel easily corrode, thus, shortening their fatigue life. The aim of this paper is to improve the fatigue strength of carbon steel gears by means of heat treatment method which was nitriding composed of 95 % nitrogen gas as well as 5 % hydrogen gas, and to investigate its properties after nitriding. Therefore, in order to find the optimum nitriding temperature to increase the hardness and corrosion resistance of gears, the gas nitriding process was conducted at two different tube furnace temperatures: low (550 °C) and high (1150 °C), both for four hours. Microstructural and mechanical property evaluation of the low and high temperature nitrided low-carbon steel BS970-080A15 were studied and the results were compared to identify which gear had better performance in terms of hardness as well as corrosion resistance. The results from Vickers hardness test and weight loss analysis proved that high temperature nitrided carbon steel is harder and more corrosion resistant than the low temperature one.     

含碳纳米管有机-无机复合涂层的制备与防护性能

为了改善铝合金材料的耐腐蚀性能, 研究了以正硅酸乙酯（TEOS）为主要原料, 加入一定量的KH-550, 并引入部分羟基化的多壁碳纳米管（MWCNTs-OH）进行复合, 以冰乙酸为催化剂, 采用溶胶---凝胶法在铝合金基体表面形成复合涂层。腐蚀电化学测试和扫描电镜分析结果表明, MWCNTs-OH的引入能够明显提高涂层的防护性能, 并有效防止涂层开裂。考察了MWCNTs-OH含量和热处理温度对涂层性能的影响。结果表明: MWCNTs-OH质量分数为0.04%、 热处理温度为130℃时制备的涂层性能最佳, 相应的试样在3.5wt%NaCl溶液中的腐蚀电流密度约为3.056×10-8A/cm2, 而同等实验条件下铝合金基体腐蚀电流密度为7.216×10-5A/cm2, 涂层的存在使腐蚀速率降低了3个数量级, 涂层对铝合金基体具有显著的防护效果。      

稀土铈对化学镀Ni-P-PTFE复合镀层防垢性能的影响

采用化学镀的方法在45号碳钢试样表面制备了稀土铈促进共沉积的Ni-P-PTFE复合镀层,利用扫描电子显微镜观察和分析了镀层的表面形貌,研究了稀土铈浓度对复合镀层的表面形貌、镀层的沉积速率、镀层中PTFE含量以及镀层防垢性能的影响。结果表明,适量稀土铈的加入使得镀层表面黑色粒子更加密集,即PTFE在镀层中的含量增加,在铈浓度为0.04g/L时达到最大;镀层的沉积速率与镀层中PTFE含量均随铈浓度的增加而呈现先升后降的趋势,在铈浓度为0.04g/L时分别达到最大值28.25μm/h和40.43%,而镀层中PTFE含量也随着沉积速率的增加而升高;铈的加入提高了镀层的防垢性能,镀层的结垢率随着铈对镀层中PTFE含量的影响而发生变化,当铈浓度为0.04g/L时,结垢率最低,仅为9.026g/m2,防垢效果最佳。     

化学镀Ni-P合金/TiO2复合膜的耐蚀性研究

在改进常规制备方法的基础上，提出化学镀/溶胶-凝胶复合法在碳钢表面制备TiO2复合膜的新技术。用衍射研究了复合膜的组织形态，采用环境扫描电镜（ESEM）表征了复合膜的表观和断面形貌，用极化电阻、阳极极化曲线测量等方法研究TiO2复合膜在0.5mol/L硫酸和0.5mol/L氯化钠溶液中的耐蚀性能。结果表明A3钢表面的TiO2复合膜耐蚀性能优良。     

Preparation and film formation mechanism of an environmental-friendly polyester/epoxy ester coil coating primer

In this investigation, we have prepared an environmental-friendly waterborne coil coating primer. Waterborne saturated polyester resin and waterborne epoxy ester resin were selected as the binder resins, and methylated melamine resin and waterborne blocked isocyanate were selected as crosslinking resins. ZnMoO₄, Zn₃(PO₄)₂, Zn₃Al(PO₄)₃, and AlH₂P₃O₁₀ were selected as the anti-corrosion pigments, and modified nano-TiO₂ particles and other fillers were also employed to further enhance the primer performance. It was found that when polyester/epoxy ester equals to 7/3; binder resins/curing agent equals to 5/1; pigments/binder resin is in range of 1.4–1.6; additives of each is in amount of 0.5 wt.%–1.5 wt.%, the obtained primer has ideal properties, such as T-bend performance and qualified adhesion, and the salt spray resistance test can reach 360 h with the primer film thickness in range of 6 μm–7 μm after baking at 224 °C for 45 s. As to the coil coating primer film formation mechanism, Fourier transform infrared spectrum analysis indicates that both the amino resin and blocked isocyanate may react with the binder resin, and such chemical reactions can make them crosslinked to form a stereo-network film, giving birth to a good overall performance of the obtained primer.     

Ni-W-ZrO2复合镀层的制备及耐腐蚀性能

采用电沉积方法制备Ni-W-ZrO₂复合镀层, 研究了微粒的分散特性及镀液中微粒含量、 电流密度、 pH值、 温度等因素对Ni-W-ZrO₂镀层沉积速率、 显微硬度、 镀层外观的综合影响, 优化得到Ni-W-ZrO₂复合镀层的电沉积工艺为: Ni-W基础镀液中ZrO₂添加量为10g/L, pH=7, 镀液温度为60~70℃, 电流密度为15A/dm2, 所获得的镀层硬度>HV800(×9.8MPa)。通过电化学技术研究了复合镀层在3.0wt%NaCl溶液中的耐腐蚀性能, 结果表明, Ni-W-ZrO₂复合镀层有明显的钝化区间。      

纳米石墨/聚氨酯复合涂层的制备及耐腐蚀性能

为研制高性能电力金具防护涂层,首先,以羟基丙烯酸树脂和异氰酸酯为主要成膜物质,纳米石墨为填料,制备了不同纳米石墨含量的纳米石墨/聚氨酯复合涂料;然后,将涂料喷涂在电力热镀锌钢上,固化干燥后得到纳米石墨/聚氨酯复合涂层;最后,测试了纳米石墨/聚氨酯复合涂层的力学性能和耐磨性,并采用模拟酸雨试验、中性盐雾试验及电化学阻抗谱（EIS）研究了纳米石墨/聚氨酯复合涂层的耐腐蚀性能。结果表明:添加纳米石墨后,涂层与热镀锌钢的附着力有所提高,纳米石墨含量为2.0wt%的纳米石墨/聚氨酯复合涂层的耐磨性比未添加纳米石墨的空白涂层提高了92%,并且涂层中纳米石墨的分布较均匀,表现出良好的耐腐蚀性能。 所得结论表明在涂层中添加适量的纳米石墨可以提高涂层的耐磨性和耐腐蚀性能,进而可将涂层用于电力金具的表面防护。      

Formation of the carbonated hydroxyapatite film on Ti-30Zr-5Al-3V bio-alloy

The Ti-30Zr-5Al-3V titanium alloy has an ultra-low Young's modulus. So, it promises great application potential as a hard-tissue implanted biomaterial. However, its surface performances need to be improved before clinical applications. In this work, a carbonated hydroxyapatite film is deposited on the surface of Ti-30Zr-5Al-3V bio-alloy using electrochemical methods. Microstructure, film-substrate adhesion, and electrochemical corrosion behavior of carbonated hydroxyapatite deposited specimens in Ringer's solution are investigated. A homogeneous, dense, and fully covered carbonated hydroxyapatite film forms on the surface after depositing at 3 V, 90 °C for 120 minutes. The formation mechanism of the carbonated hydroxyapatite film on the micro-nano structure surface is revealed. The corrosion performance of carbonated hydroxyapatite deposited specimens in Ringer's solution is evaluated by using potentiodynamic polarization curves. The carbonated hydroxyapatite deposition obviously enhanced the corrosion resistance of the Ti-30Zr-5Al-3V bio-alloy.     

The impact of aging and drag-finishing on the surface integrity and corrosion behavior of the selective laser melted maraging steel samples

The maraging steel components fabricated using the selective laser melting process exhibit remarkable static strength. However, high pore density and large surface imperfections impede their overall mechanical and chemical performance. Thus, the components are often post-treated with mechanical- and thermal-based treatments to overcome their inherent imperfections and enhance their final mechanical properties. Although the post-processing treatments are useful in enhancing the selective laser melted components’ mechanical performance, their effect on corrosion behavior is not comprehensively evaluated. In this study, the selective laser melting prepared maraging steel samples’ corrosion behavior was examined in the as-built condition and compared with the post-processed samples subjected to aging and drag finishing operations. Compared to the as-built condition, both aging and drag-finishing post-processing treatments increased the selective laser melting samples’ corrosion even though the surface integrity was improved.     

变形热处理对Zr-1.0Nb合金耐腐蚀性能的影响

为了探究显微组织对Zr-1.0Nb合金耐腐蚀性能的影响,将Zr-1.0Nb合金样品分别进行680℃/500℃、680℃/560℃、800℃/500℃、800℃/560℃和1000℃/560℃五种变形热处理,然后在350℃、16.8 MPa、0.01mol.L-1的L iOH水溶液中腐蚀,并用透射电镜(TEM)研究其显微组织.其中800℃-1 h/冷轧/500℃-30 h处理样品的耐腐蚀性能最好,基体αZr中Nb元素固溶含量最低.通过变形热处理降低基体αZr中Nb元素固溶含量是提高Zr-1.0Nb合金耐腐蚀性能的一个关键因素.     

Effects of aluminum content and mechanical nano-alloying time on the preparation of titanium-aluminum composite coatings on magnesium-lithium alloy

A titanium-aluminum composite coating was successfully fabricated on magnesium-lithium alloy substrate by mechanical nano-alloying treatment (SMNAT). The effects of aluminum content and mechanical nano-alloying time on the microstructure and properties of titanium-aluminum composite coatings were investigated. The experimental results showed that the ratio of titanium-aluminum powder has a significant effect on the preparation of the coating. Low aluminum content and high aluminum content in the mixture powder resulted in the formation of the coatings with inhomogeneous thickness. The titanium-aluminum ratio of 3 : 1 was considered to be optimal for fabricating the coating with homogeneous thickness under the selected milling parameters. The hardness of top surface layer on titanium- aluminum coatings decreased from 292.0 HV 0.01 to 121.4 HV 0.01 with the increase of aluminum content. Additionally, the prolongation of treatment time facilitated to increase the thickness and density of the coatings, resulting to enhance their hardness and corrosion resistance.     

Computational and experimental investigation on mechanical behavior of zirconia toughened alumina and nickel powder reinforced EN31 based composite material

In the present investigation, EN31 steel alloy based composite material has been developed using zirconia toughened alumina as primary reinforcement material and Ni powder as secondary reinforcement material. The weight percent of zirconia toughened alumina varied from 1.25 % to 10 %. While Ni powder weight percent has been kept uniform (2.5 %). The microstructure of the composite material developed showed uniform distribution of reinforcement particles. Results showed that wettability of zirconia toughened alumina particles improved by adding the nickel particles in EN31 steel alloy. Tensile strength and hardness after the heat treatment were found to be 899 MPa and 120.12 BHN respectively for EN31/6.25 wt.% zirconia toughened alumina/2.5 wt.% nickel composite material. Results showed that tensile strength and hardness of EN31 steel alloy improved about 46.17 % and 100.20 % respectively after adding 6.25 % zirconia toughened alumina and 2.5 % nickel powder. However, ductility reduced by adding the zirconia toughened alumina and nickel powder in EN31 steel alloy. The Finite element analysis has also been carried out to predict the deformation and damage behavior of investigated material during tensile test process. In addition, Brinell hardness test process finite element analysis model is also developed. The finite element analysis results are in good agreement with experimental results with 5 % of percentage difference.     

热处理对玻璃纤维布/聚苯硫醚非织造布复合板材力学性能的影响

以玻璃纤维布和聚苯硫醚（PPS）非织造布分别作为增强体和树脂基体原料,采用热压成型法制备出玻璃纤维布/PPS非织造布复合板材,然后在烘箱中进行热处理。利用万能试验机（Instron）、XRD、偏光显微镜（PLM）和SEM等手段对玻璃纤维布/PPS非织造布复合板材的力学性能、结晶度、晶粒类型和尺寸及微观形貌等进行了测试和表征。结果表明：随着热处理温度和时间的提高,玻璃纤维布/PPS非织造布复合板材的弯曲强度、弯曲模量和缺口冲击强度得到明显提高。当热处理温度为220℃、热处理时间为2 h时,其力学性能最佳,其弯曲强度、弯曲模量和缺口冲击强度分别达到285.7 MPa、7.8 GPa和85.0 MPa。和未进行热处理的玻璃纤维布/PPS非织造布复合板材相比,分别提高了63.2%、469.0%和37.8%。微观形貌结果表明,玻璃纤维布/PPS非织造布复合板材界面粘结得到了明显改善。