微束等离子喷涂气体对HA涂层结晶度的影响

采用微束等离子喷涂方法,分别选用工业纯氩气和含50%氦气的氦氩混合气体为工作气体,在Ti-6Al-4V基体上制备羟基磷灰石涂层.通过SEM和XRD对涂层形貌、相组成和结晶度进行研究.结果表明,两种工作气体均可以制备杂质相含量少且不产生TTCP(磷酸四钙)和CaO等杂质相的涂层,结晶度高于70%,对植入体在体内的稳定性有利.采用氦氩混合气体为工作气体的微束等离子弧热焓值高于氩气工作气体,前者涂层中的结晶相主要以再结晶的为主,后者结晶相以大量未熔HA内核为主.     

NiCrAlY涂层的表面状态对高温氧化行为的影响

将原始喷涂态和表面抛光的NiCrAlY涂层在1050℃恒温氧化300h，利用XRD、SEM，EDS方法，测定涂层的氧化物及其相转变，分析表面氧化膜的生长破坏行为，结果表明：两种涂层在1050℃保温，在150h以内均能生成α-Al2O3氧化膜，150h后，抛光态涂层保护性氧化膜被破坏，抗氧化能力下降，喷涂态涂层表面粗糙，连续Al2O3保护膜的形成较晚，氧化早期氧化膜中存在微裂纹，可释放应力，有利于氧化膜与涂层的结合。氧化动力学曲线符合抛物线规律，氧化至300h，表面氧化膜只有少量微裂纹，无剥落，说明喷涂涂层的长期恒温抗氧化能力比抛光态涂层强。     

Prediction of surface and interfacial tension based on thermodynamic data and CALPHAD approach

In this article, following a brief introduction concerning experimental measurements of surface and interfacial tensions, methods for calculating surface tension and surface segregation for binary, ternary, and multicomponent high-temperature melts based on Bulter＇s original treatment [ 1] and on available physical properties and thermodynamic data, especially excess Gibbs free energies of bulk phase and surface phase versus temperature obtained from thermodynamic databases using the calculation of phase diagram （CALPHAD） approach, with special attention to the model parameter β, have been described. In addition, the geometric models can be extended to predict surface tensions of multicom- ponent systems from those of sub-binary systems. For illustration, some calculated examples, including Pb-free soldering systems and phase-diagram evaluation of binary alloys in nanoparticle systems are given. On the basis of surface tensions of high-temperature melts, interracial tensions between liquid alloy and molten slag as well as molten slag and molten matter can be calculated using the Girifalco-Good equation [2]. Modifications are suggested in the Nishizawa＇s model [3] for estimation of interracial tension in liquid metal （A）/ceramics （MX） systems so that the calculations can be carried out based on the sublattice model and thermodynamic data, without deliberately differentiating the phase of MX at high temperature. Finally, the derivation of an approximate expression for predicting interfacial tension between the high-temperature multicomponent melts, employing Becker＇s model [4] in conjunction with Bulter＇s equation and inteffacial tension data of the simple systems is described, and some examples concerning pyrometallurgical systems are given for better understanding.     

氧化铝表面粗糙度对熔融铅润湿性及表面张力的影响

表面粗糙度是高温下的液态金属/陶瓷润湿性的重要影响因素.在923～1123 K的温度范围内研究氧化铝表面粗糙度对铅液滴接触角、接触直径、液滴高度、表面张力的影响.在冷却后使用SEM观察铅/基底界面的微观结构.通过使用几何平均法计算氧化铝基板的表面自由能进而解释铅液滴润湿行为的机理.结果表明,在铅液滴/氧化铝陶瓷系统中,...     

熔融Ni-Co合金表面张力的测量与分析

Ni-Co高温合金广泛用于生产燃气涡轮机叶片和热交换器等工作于高温和腐蚀环境的零部件,采用改良静滴法测定了1773～1873K温度范围内熔融Ni,Ni-(5～10)%Co合金在Al2O3基板上Ar 3%H2气氛下的表面张力.熔融Ni,Ni-(5～10)%Co合金的表面张力随着温度的升高而降低.在此基础上采用Butler模型推导了表面张力随温度与浓度的变化,计算了合金体系中元素的偏聚.结果表明,Co在合金表面的浓度低于在体相的浓度.     

A new method of fast measuring surface tension of melt cast iron and its application in graphite shape identification

1. Introduction In a casting process of alloy, many casting process parameters, such as refining and inoculating, gas isolation, mould filling ability and the surface roughness of casting, relate to surface tension of alloy. So, it has been approa- ched for a long time of interest by foundrymen and metallurgists to invent an effective method of fast measuring surface tension. Traditional methods of measuring surface tension can be classified into static and dynamic methods. Static method calcu…     

Nanoindentation on the surface of thermally sprayed coatings

The ability to quantify surface mechanical properties is valuable for assessing the quality of thermal spray coatings. This is especially important for prostheses where loading is placed directly on the surface. Hydroxyapatite was classified to small (20-40 μm), medium (40-60 μm) and large (60-80 μm) particle sizes and thermal sprayed to produce a coating from spread solidified hydroxyapatite droplets. It was revealed for the first time, that nanoindentation can be successfully used to determine the hardness and elastic modulus on the surface of well spread solidified droplets at the hydroxyapatite coating surface. Comparison with indentation results from polished cross-section exhibited comparable values and statistical variations. The hardness was 5.8 ± 0.6, 5.4 ± 0.5 and 5.0 ± 0.6 GPa on coatings produced from small, medium and large sized powder. Similarly, the elastic modulus decreased from 121 ± 7, 118 ± 7 to 114 ± 7 GPa, respectively. Use of several indentation loads gave comparable results with sintered hydroxyapatite suggesting good inter-splat bonding within the coating. MicroRaman spectroscopy and X-ray diffraction confirmed a larger degree of dehydroxylation for the smaller particles also revealing a lower elastic modulus. This shows the influence of particle size and possibly dehydroxylation of hydroxyapatite on the mechanical properties of the coating surface.     

由铁液表面张力预测和防止灰铸铁针孔缺陷

介绍了灰铸铁件针孔缺陷形成的原因及其与铁液表面张力的关系：认为表面张力越大,针孔缺陷越难形成;阐述了表面张力的测量方法,并提出了表面张力防止针孔的措施。     

Influence of surface roughness on performance of zinc-rich paint coatings

The influence of surface roughness on the performance of zinc-rich paint(ZRP) coatings was studied.Electrochemical impedance spectroscopy(EIS) measurements were used to assess the corrison prevention performance of the ZRP coatings.Furthermore,the EIS data of the steel-ZRP-sea water system were interpreted according to equivalent circuit models and the corresponding parameters were derived to assess the coating deterioration with time.The results show that the rougher surface favors better protection effect of the ZRP coatings.The protection potential of ZRP coatings for the standards and codes of practice is -0.78V(vs SCE).     

离子轰击下高碳钢的脱碳对随后渗金属的影响

研究了T8钢等离子体脱碳对随后渗金属的影响. 介绍了两种处理工艺, 一种是脱碳后渗金属, 另一种是直接渗金属. 结果表明, 在离子轰击下, 高碳钢表层产生严重的脱碳层, 脱碳层的存在对随后的渗金属过程有着很大的影响. 脱碳后渗金属, 渗层厚度达80μm; 直接渗金属, 渗层厚度仅15μm. 在两种渗金属条件下, 表面合金层的非碳化物形成元素Co含量差别不是很大, 而强碳化物形成元素W和Mo的含量却有着显著差异, 直接渗金属的, 表层W和Mo含量几乎为零, 而脱碳后渗金属的, 表层W和Mo总量最大达到6%左右.     

Effect of surface preparation on the durability of NiCoCrAlY coatings for oxidation protection and bond coats for thermal barrier coatings

A principal concern with alumina‐forming coatings for high‐temperature oxidation protection and bond coats (BCs) for ceramic thermal barrier coatings (TBCs) used in gas turbines is the spalling of the alumina scales during service. This paper describes the effects of BC surface preparation on the durability of NiCoCrAlY coatings exposed under thermal cycling conditions. State‐of‐the‐art TBC systems deposited by electron beam physical vapor deposition (EBPVD) with NiCoCrAlY overlay BCs were found to fail as the result of defects which included transient oxides, defects in the BC surface, defects in the as‐deposited microstructure of the TBC, and excessive oxidation of reactive element additions. In some instances, the TBC life was greatly extended by surface treatments, such as fine polishing. The oxidation behavior of NiCoCrAlY coatings, absent a TBC, was found to be sensitive to Y content and to surface preparation. This paper describes how a variety of surface treatments affected coating lives and failure mechanisms.     

冷轧卷取头尾张力对带钢划伤的影响及其控制措施

针对某1 420 mm冷连轧机组成品卷带钢头尾出现划伤的问题,从卷取张力波动入手,首先对头尾起步建张对带钢挫、划伤缺陷的影响进行了理论分析,然后分别选取正常卷带钢和问题卷带钢的工艺参数进行对比分析,在此基础上分析了头尾建张对带钢挫、划伤缺陷的影响。结果表明,该1 420 mm冷连轧机卷取机组存在张力波动问题,首次张力波动发生在距离钢卷尾部约150 m处,第2次张力波动发生在距尾部约40 m处;张力波动使带钢卷取得不够紧密,会产生滑移而形成松动层,加上运输等外部因素,造成松动层处层与层之间相互摩擦、碰撞,最终造成带钢挫、划伤缺陷。通过对卷取头尾张力波动不大于0.5 MPa、张力变化率不大于1.24 N·s^-1,速度变化率不大于12 m·s^-2,紧密系数大于1.25的控制,带钢松卷和挫、划伤缺陷问题得到明显改善,保证了产品质量。     

钎料表面微结构对糊状钎剂黏附性的影响

文中采用金相显微镜、润湿角测定仪、表面张力仪等分析手段,分析了钎料表面微结构对糊状钎剂黏附性的影响.结果表明,糊状钎剂可在擦洗、擦洗+精轧两种钎料表面黏附润湿或浸湿,但不能自行铺展润湿.与擦洗钎料相比,糊状钎剂在擦洗+精轧钎料表面具有更大的接触角滞后、糊状钎剂黏附量,且黏附层分布相对均匀,收缩坑较少.糊状钎剂在擦洗、擦洗+精轧钎料表面的黏附功和黏附张力,分别为106.39,29.89和110.28,33.78 mN/m.糊状钎剂在擦洗+精轧钎料表面具有更大的黏附功和黏附张力,是其表面黏附量大、黏附层均匀、收缩坑少的主要原因.     

Effect of steam treatment during plasma spraying on the microstructure of hydroxyapatite splats and coatings

The major problems with plasma sprayed hydroxyapatite (HA) coatings for hard tissue replacement are severe HA decomposition and insufficient mechanical properties of the coatings. Loss of crystalline HA after the high-temperature spraying is due mainly to the loss of OH⁻ in terms of water. The current study used steam to treat HA droplets and coatings during both in-flight and flattening stages during plasma spraying. The microstructure of the HA coatings and splats was characterized using scanning electron microscope, Raman spectroscopy, Fourier transform IR spectroscopy, and x-ray diffraction. Results showed that a significant increase in crystallinity of the HA coating was achieved through the steam treatment (e.g., from 58 to 79%). In addition, the effects were dependent on particle sizes of the HA feedstock, more increase in crystallinity of the coatings made from smaller powders was revealed. The Raman spectroscopy analyses on the individual splats and coatings indicate that the mechanism involves entrapping of water molecules by the individual HA droplets upon their impingement. It further suggests that the HA decomposition has already taken place before the impingement of the droplets on precoating or substrate. The improvement in crystallinity and phases, for example, from tricalcium phosphate and amorphous calcium phosphate to HA, was achieved by reversing the HA decomposition through providing extra OH⁻. Furthermore, the steam treatment during the spraying also accounts for remarkably increased adhesion strength from 9.09 to 23.13 MPa. The in vitro testing through immersing the HA coatings in simulated body fluid gives further evidence that the economic and simple steam treatment is promising in improving HA coating structure. This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials Park, OH, 2006.     

激光表面重熔对热喷涂铝涂层微观结构及其阻氢性能的影响

采用Ｘ射线衍射仪、扫描电镜及热充氢等方法,研究了激光重熔对不锈钢表面热喷涂铝涂层的微观结构及其阻氢性能的影响。结果表明,激光重熔后涂层组织均匀、致密,主要由ＡｌＦ３（Ｎｉ,Ｃｒ）固溶体、ＣｒＦｅＮｉ奥氏体等相组成,而且涂层与基体形成了良好的冶金结合。此外,激光表面重熔后涂层的阻氢性能亦得到改善。     

5052铝合金表面化学镀Ni-P镀层的组织与性能

利用化学镀在5052铝合金表面制备了Ni-P镀层,通过SEM、EDS和XRD等手段对镀层表面和界面的形貌、物相、组成、结构和性能进行了表征和分析。结果表明:化学镀Ni-P合金镀层为非晶态,成分以Ni为主,由直径为10~50-m的颗粒组成,颗粒分布较均匀,界面结合状态良好;化学镀对表面粗糙度的影响在500 nm以内,镀后镀层表面粗糙度Ra为384.49 nm;镀层残余应力状态为拉应力,其值达到(521±168.0)MPa。     

Effect of Nd and La on surface tension and wettability of Sn-8Zn-3Bi solders

Maximum bubble pressure measurement was employed to evaluate surface tension of Sn-8Zn-3Bi- （0-0.15）Nd and Sn-8Zn-3Bi-（0 -0. 15）La solder melts. Wetting balance method was used to measure wetting force and wetting time on Cu substrate of the two group solders. The experimental results show that minute amount of Nd or La addition to Sn-8Zn-3Bi solder causes significant decrease of the surface tension of the solder melts at 200 - 240 ℃ and Nd addition is more effective on reduction of surface tension than that of La. Nd or La addition has the effect on enhancing the wetting force of the solder melts on Cu substrate, which results from the de- crease of interracial tension between the solder melt and Cu substrate. The wetting force reaches the maximum when 0.1% Nd is added to the base alloy. The contact angle between Sn-8Zn-3Bi base solders and Cu substrate decreases with the addition of Nd or La and the minimum of the contact angle is obtained from the solder with 0.1% Nd addition.     

成形磨削表面粗糙度的试验研究

数控成形磨削技术是近年来国内外迅速发展的一种新型的加工技术,其高效精密的加工方式在机械工程上有着极其广泛的应用。本文首先分析了成形磨削过程中各磨削参数对磨削表面粗糙度的影响,进而对金刚石滚轮修整轨迹进行推导和分析,验证了修整条件和磨削条件对成形磨削表面粗糙度的影响。本文运用正交回归设计方法建立了表面粗糙度R。对磨削工艺参数的回归方程,并推导出模型公式Ra=2．34×V(?)/-0.45×Vω/0.08×aρ/0.15,找出磨削工艺参数对Ra的影响程度,在实际应用中可以对Ra进行预测。在研究修整轨迹在某点的曲率半径ρ与修整速比q的变化关系时,测定了不同的修整速比p,每转进给量与表面粗糙度的变化关系。研究结论可用于分析和预测fd或限制工件表面粗糙度。