挤压铸造铝锌镁铜系合金的热处理工艺对性能的影响

铝锌镁铜系合金是一种重要的结构材料,通过热处理工艺试验和性能测试、组织分析,证明铝锌镁铜系合金对淬火冷却速度非常敏感,将淬火转移时间控制在15s以内可保证合金的性能.     

热处理对低压冷喷涂铜铝复合涂层耐腐蚀性能的影响

通过低压冷喷涂技术在45号钢基体表面制备了铜铝复合涂层,然后在不同温度对涂层进行了热处理.采用静态压痕法和扫描电镜(SEM)表征热处理前后涂层的显微硬度和微观形貌;采用腐蚀浸泡试验、铜加速乙酸盐雾(CASS)试验研究热处理前后涂层的耐腐蚀性能.结果表明:当热处理温度为450℃时,铜铝复合涂层内铜、铝元素发生了明显的扩散...     

AZ31镁合金铝涂层机械研磨振动热扩散研究

以AZ31镁合金热喷涂铝涂层为研究对象,用自制的振动热扩散装置,进行一定温度热扩散或在热扩散的同时进行振动机械研磨处理,研究比较了振动热扩散对镁合金热喷铝涂层的影响.采用金相显微镜、扫描电子显微镜观察涂层表面、截面形貌,对涂层界面进行能谱分析,利用显微硬度计测量不同工艺下涂层与镁基体界面处硬度变化,利用X射线衍射分析涂层与基体界面处扩散区域相组成,用电化学工作站测得涂层极化曲线,通过盐水浸泡分析比较了不同工艺处理后镁合金的耐腐蚀性.结果表明:镁合金喷铝涂层经360～400℃保温2h热扩散或振动热扩散(机械研磨热扩散),在涂层与镁基体的界面处镁铝原子有不同程度的互扩散,并有镁铝Al12Mg17相生成,界面硬度有极大提高,振动热扩散使涂层明显致密化并形成连续析出相,能有效提高涂层的耐腐蚀性能.     

镁合金表面电弧喷铝层的微观结构及界面分析

为获得性能优良的镁合金表面复合涂层,用自动送进的双铝丝做两个电极产生电弧,用压缩空气把熔化的铝熔滴喷到AZ91D镁合金表面,形成镁铝复合涂层。通过选用不同电压和气压进行喷涂试验,分析其对涂层组织性能的影响规律,找出最佳工艺参数。利用现代分析手段研究涂层的微观结构及界面特点,并通过测定涂层电极电位和盐雾试验分析涂层的耐腐蚀性能。结果表明,一定的电压和气压条件可使涂层致密,界面有新生组织,涂层中产生了小于50nm的纳米级晶团束和微米级层片状双重结构,涂层耐腐蚀性能明显优于镁合金基体。     

镁合金电火花沉积改性层性能及组织结构的研究

应用电火花沉积设备在AZ91D镁合金表面沉积纯铝涂层进行表面改性处理,研究了电火花沉积工艺参数以及前处理对沉积改性层性能和组织结构的影响;并结合扫描电镜、中性盐雾试验等研究手段对镁合金改性涂层的微观表面形貌、截面形貌、腐蚀情况以及显微硬度进行了分析和对比;同时,也对镁合金表面沉积纯铝涂层的沉积机理和沉积层改善基体耐腐蚀性、硬度进行分析与讨论。研究结果表明:电火花沉积工艺参数及预处理对AZ91D镁合金表面沉积纯铝涂层的组织结构、微观形貌特点有重要影响;电火花沉积工艺参数的降低以及沉积前对母材和电极的预热处理,涂层表面显微硬度较基材有了较大程度的提高;同时,强化层组织结构均匀致密、涂层厚度适中、涂层内部裂纹孔洞等缺陷明显降低,与镁合金基材相比,表现出较好的耐腐蚀性能。     

铝合金表面电弧喷涂铝涂层工艺与性能

采用电弧喷涂工艺在6061铝合金基体表面喷涂高纯铝涂层,利用金相显微镜对涂层的组织进行观察,分析了基体与涂层的结合方式,测量了涂层的孔隙率.并采用质量分数为5%的NaCl溶液浸泡试验、盐雾试验和电化学试验,检验了涂层的耐腐蚀性.结果表明,利用电弧喷涂技术可以在6061铝合金基体表面形成均匀、致密、孔隙率低、结合良好的高纯铝涂层;高纯铝涂层耐腐蚀性较好,对铝合金基体起到了保护作用,涂层经过封孔工艺处理后保护作用更好.     

定向凝固低压涡轮叶片渗铝硅工艺研究

在工厂条件下对ＡＳＬ－５铝硅涂层工艺进行了试验，确定了工艺参数。分析研究了铝硅涂层组织结构。试验结果表明该涂层可以显著提高涡轮叶片的抗氧化和抗热腐蚀性能，涂层对基材的机械性能影响不大。     

钙镁橄榄石等离子涂层及其生物活性研究

采用大气等离子喷涂技术,在Ti-6A1-4V基体上制备了钙镁橄榄石涂层,研究了热处理对涂层组织结构及结合强度的影响,并对此材料作了体外模拟液浸泡及细胞共培养试验.结果表明,热处理前涂层的结晶度较低,热处理(400～900℃)能有效降低涂层的孔隙率、提高涂层的结合强度.在700℃下热处理后,涂层具有最低的孔隙率,结晶度较高,组织比较均匀,膨胀系数与基体材料接近,因而具有最高的结合强度(达到37 MPa)和很好的稳定性.此涂层在模拟体液中浸泡7 d后表面明显有磷灰石出现.成骨细胞在材料表面的贴壁试验说明,细胞在材料表面生长旺盛,表明该涂层具有很好的生物相容性.     

镁/铝异种金属填充式摩擦点焊接头特性

采用填充式摩擦点焊技术对镁/铝异种金属进行工艺试验,并对点焊接头的力学性能和微观组织进行分析.结果表明,当采用合理的搭接接头设计和工艺参数进行镁/铝异种金属摩擦点焊时,可获得表面平整、抗剪切能力强的焊点,其焊点剪切力可达1865 N.组织分析发现,在焊核与镁母材之间的竖直界面处易出现少量的孔洞、微裂纹等缺陷,接头的断裂正发生在该区;而在镁/铝之间的水平界面结合良好,存在一定厚度的界面层组织,且该界面层组织的硬度要比两侧母材的硬度明显高很多,这与摩擦点焊过程中脆硬相的金属间化合物的形成有关.     

铝青铜QAl10-4-4热处理工艺性能研究

为了提高航空铝青铜QAl10-4-4材料的机械加工及使用性能,对热轧状态铝青铜QAl10-4-4进行热处理工艺试验,通过硬度检测和金相组织分析,优化了工艺参数。当布氏硬度要求250~300HBS时,采用900℃固溶和430~530℃时效,可获得最佳的力学性能和金相组织。为制定铝青铜QAl10-4-4的热处理工艺提供了重要依据。     

A Study of the Corrosion Resistance of Pump–Compressor Pipes with a Diffusion Zinc Coating under the Complicated Conditions of Gas-Producing Wells

The results of corrosion tests of diffusion zinc coatings under the complicated corrosion and erosion conditions of gas-production wells are presented. The slowdown of the anodic process of the solution of a coating and its salt passivation in model solutions was shown by the electrochemical research. It was established that the corrosion rates of diffusion zinc-coated 36G2F steel samples were 4.1–6.1 times lower than those of samples without coating. The corrosion resistance and the operational reliability of pump–compressor pipes can be increased by using protective duplex system combining a diffuse zinc coating (protective layer) and an upper layer of a polymer coating (barrier layer).     

双层辉光等离子制备TiN渗镀层的耐蚀性能

利用双层辉光等离子表面合金化技术,在Q235钢表面直接合成TiN渗镀层,该渗镀层由TiN颗粒均匀分布的扩散层及表面TiN沉积层组成。将TiN渗镀层与Q235钢基体和1Cr18Ni9Ti不锈钢在4%的NaOH溶液、l mol/L H2SO4溶液和3.5%NaCl溶液中分别进行电化学腐蚀对比试验。结果表明:在4%的NaOH溶液中,TiN渗镀层的耐蚀性能比Q235钢提高了26.8倍,与1Cr18Ni9Ti不锈钢相当;在l mol/L H2 S04溶液中,TiN渗镀层耐腐蚀性能比Q235钢提高了10.5倍,比1Crl8Ni9Ti不锈钢提高了1.65倍;在3.5%的NaCl溶液中,TiN渗镀层耐腐蚀性能比Q235钢提高了10.3倍,但比1Crl8Ni9Ti不锈钢稍差。TiN渗镀层耐酸碱性溶液腐蚀性能要比耐盐溶液腐蚀性能强。     

NiAl/NiCoCrAlY/8YSZ复合喷涂层的微观结构与性能研究

目的提高金属/陶瓷隔热涂层体系在海洋环境下的耐腐蚀性能。方法利用冷喷涂方法制备NiAl复合打底层和Ni CoCrAlY粘结层,与等离子喷涂制备的8YSZ陶瓷层构成适用于海洋环境的多层结构耐蚀隔热涂层体系。利用FE-SEM分别观察喷涂态粘结层和陶瓷层的表面、横截面形貌,通过EDS分析涂层元素分布;利用XRD分析表征涂层的物相组成;借助万能材料试验机,采用拉伸法测试涂层结合强度;利用热循环试验和焰流冲刷试验测试涂层的耐高温性能。结果微观分析表明,冷喷涂制备的NiAl复合打底层和Ni CoCrAlY粘结层形貌致密,涂层材料未发生明显氧化,颗粒变形程度不一,粘结层与基体间的结合强度约为18.4 MPa,粘结层与8YSZ陶瓷层界面结合紧密。陶瓷层物相结构和成分稳定,涂层经12次热震循环和1000个周期的高温焰流冲击后,表面未出现开裂、起皮和脱落。结论采用冷喷涂法和等离子喷涂法联合制备的耐蚀隔热复合涂层体系具备良好的耐热性和耐腐蚀性。冷喷涂制备的金属涂层结构致密,孔隙率低,与陶瓷层结合良好,能够有效提高涂层体系在腐蚀性环境中的耐蚀性能。NiAl复合涂层可以缓解Ni CoCrAlY粘结层和铝合金基材间的热匹配问题,增强涂层的结合性能。     

Effect of chromium on the protective properties of aluminide coatings

Aluminide and chromaluminide diffusion coatings on nickel and a nickel-base superalloy, EI 867, were subjected to different corrosion tests consisting of oxidation under isothermal and thermal cycling conditions, and oxidation in the presence of fused sodium sulfate. It was found that chromium present in the surface layers of aluminide coatings has a beneficial effect on their resistance to oxidation and hot corrosion.     

热氧化提高钛及钛合金表面性能的研究进展

热氧化作为一种引起广泛关注的钛及钛合金表面改性技术,具有工艺简单、原位生长、薄膜厚度大以及性价比高等特点。通过热氧化表面处理技术能够在钛及钛合金表面形成较厚的由钛氧化层和氧的扩散层组成的硬质氧化膜,氧化膜对材料起到有效的保护作用,提高了材料单一耐磨性、耐蚀性以及生物活性或综合表面性能。从热氧化工艺原理及其对钛及钛合金表面性能影响的角度,综述了热氧化对钛及钛合金表面硬度、耐磨性、耐蚀性、生物相容性等性能影响的研究进展,并对其以后的研究方向进行了展望。通过合理控制氧化温度、氧化时间、氧化气氛及冷却方式等工艺条件,从而得到连续、致密且疲劳性能较好的金红石型TiO_2和氧的扩散层是改善钛及钛合金性能的关键。将热氧化处理与其他工艺相结合,针对性地提高膜层厚度及材料的耐磨性、耐蚀性、生物性能等,以实现复合涂层的制备将是热氧化在钛及钛合金性能改善方面的研究方向。     

热障涂层失效机理、改进方法及未来发展方向

热障涂层(Thermal Barrier Coatings,TBCs)是用于航空发动机及燃气轮机的一种高效功能性隔热涂层,常用材料为氧化钇(质量分数6％～8％)部分稳定氧化锆(YSZ).首先,从TGO生长、高温烧结、CMAS腐蚀、盐雾腐蚀和热膨胀失配等方面介绍了YSZ的失效机理,以上因素会从不同程度上造成涂层分层、开裂...     

Corrosion behaviors of arc spraying single and double layer coatings in simulated Dagang soil solution

Three kinds of single layer coatings of Zn, Zn15Al, 316L stainless steel and two kinds of double layer coatings with inner layer of Zn or Zn15Al and outer layer of 316L stainless steel by arc spraying were developed to protect the metal ends of prestressed high-strength concrete (PHC) pipe piles against soil corrosion. The corrosion behaviors of the coated Q235 steel samples in the simulated Dagang soil solution were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and natural immersion tests. The results show that the corrosion of the matrix Q235 steel is effectively inhibited by Zn, Zn15Al, Zn+316L and Zn15Al+316L coatings. The corrosion rate value of Zn15Al coated samples is negative. The corrosion products on Zn and Zn15Al coated samples are compact and firm. The corrosion resistance indexes of both Zn and Zn15Al coated samples are improved significantly with corrosion time, and the latter are more outstanding than the former. But the corrosion resistance of 316L coated samples is decreased quickly with the increase in immersion time. When the coatings are sealed with epoxy resin, the corrosion resistance of the coatings will be enhanced significantly.     

Effects of annealing heat treatment on the corrosion resistance of Zn/Mg/Zn multilayer coatings

Zn coatings alloyed with magnesium offer superior corrosion resistance compared to pure Zn or other Zn-based alloy coatings. In this study, Zn/Mg/Zn multilayer coatings with various Mg layer thicknesses were synthesized using an unbalanced magnetron sputtering process and were annealed to form Zn-Mg intermetallic phases. The effects of the annealing heat treatment on the corrosion resistance of the Zn/Mg/Zn multilayer coatings were evaluated using electrochemical measurements. The extensive diffusion of magnesium species into the upper and lower zinc layer from the magnesium layer in the middle of the coating was observed after the heat treatment. This phenomenon caused (a) the porous microstructure to transition into a dense structure and (b) the formation of a MgZn₂ intermetallic phase. The results of the electrochemical measurements demonstrated that the heat treated Zn/Mg/Zn multilayer coatings possessed higher levels of corrosion resistance than the non-heat treated coatings. A Zn/Mg/Zn multilayer coating with MgZn₂ and (Zn) phases showed the best corrosion resistance among the heat treated coatings, which could be attributed to the reduced galvanic corrosion effects due to a small potential gradient between the MgZn₂ and zinc.     

Corrosion Properties of Cold-Sprayed Tantalum Coatings

Cold spraying enables the production of pure and dense metallic coatings. Denseness (impermeability) plays an important role in the corrosion resistance of coatings, and good corrosion resistance is based on the formation of a protective oxide layer in case of passivating metals and metal alloys. The aim of this study was to investigate the microstructural details, denseness, and corrosion resistance of two cold-sprayed tantalum coatings with a scanning electron microscope and corrosion tests. Polarization measurements were taken to gain information on the corrosion properties of the coatings in 3.5 wt.% NaCl and 40 wt.% H₂SO₄ solutions at room temperature and temperature of 80 °C. Standard and improved tantalum powders were tested with different spraying conditions. The cold-sprayed tantalum coating prepared from improved tantalum powder with advanced cold spray system showed excellent corrosion resistance: in microstructural analysis, it showed a uniformly dense microstructure, and, in addition, performed well in all corrosion tests.     

Corrosion behaviour of nanocomposite TiSiN coatings on steel substrates

Nanocomposite TiSiN coatings were deposited on tool steels. Detailed mechanisms that govern the corrosion of these coated steels were revealed, following immersion tests in a 70% nitric acid solution. Pitting originated preferentially from coating defect sites and expanded with increasing immersion time. Both Young’s modulus and hardness measured by nanoindentation decreased as the corrosion damage intensified. A thin oxide layer formed from the thermal annealing of the as-deposited samples at 900 °C was found to be effective against corrosive attack. In addition, compressive residual stress was noted to suppress the propagation of corrosion-induced cracks. The role of residual stress in controlling the corrosion resistance of these ceramic-coated steels is clarified by finite element analysis.