Comparison and Applications of DPV-2000 and Accuraspray-g3 Diagnostic Systems

Comparative in-flight measurements of particles plasma sprayed by F4 and Triplex II guns were carried out using the diagnostic systems DPV-2000 and Accuraspray-g3. The comparison of mean particle velocities and temperatures as well as intensity profiles of the plume show a good agreement confirming their accuracy. However, the varying operating principles especially the deceased dimensions of the measurement volumes have to be considered carefully when evaluating the results. Furthermore, some applications of the diagnostic systems DPV-2000 and Accuraspray-g3 are shown. Finally some application limits, which were identified for certain powder compositions at higher plasma power levels will be discussed.     

A Study of Wire Breakup and In-Flight Particle Behavior During Wire Flame Spraying of Aluminum

Although wire flame spraying has been used for many years, there has been relatively little attention given to understanding the process dynamics. In this work, imaging of the molten wire tip, particle imaging using the Oseir SprayWatch system and particle capture (wipe tests) have all been employed to quantify plume behavior. Aluminum wire feedstock is melted and then breaks up close to the exit of the spray nozzle in a non-axisymmetric manor. The mean velocity and diameter of the particles detected by the SprayWatch system change little with standoff distance with values of approximately 280 m/s and 70 µm, respectively, for the spray parameters employed. The particle diagnostic system could not detect particles ?45 µm in diameter, and it is estimated that these account for no more than 53% of the sprayed material. Overall, wire flame spraying generates a surprisingly stable particle stream.     

Comparison of In-Flight Particle Properties, Splat Formation, and Coating Microstructure for Regular and Nano-YSZ Powders

The relationship between atmospheric pressure plasma spray parameters and in-flight particle characteristics was determined. The morphologies of individual splats and the coating microstructure were studied for different stand-off distances and arc currents. Coating cross-sectional analysis showed that the total porosity of the coating increased with decreasing arc current, and increasing stand-off distance. Two different materials were used: the regular (r-YSZ) feed stock and the nano size (n-YSZ) agglomerated powder. The results illustrate that the r-YSZ coating has higher total porosity at higher arc currents than n-YSZ coating. The splat flattening degree and circularity was examined at different substrate temperatures for both powders. The results indicate that the flattening degree increased at high temperatures for the two materials, but the values for n-YSZ were higher than those for the r-YSZ. This study showed the operating regimes in which the use of n-YSZ yields improved coating properties.     

The Effect of Torch Hardware on Particle Temperature and Particle Velocity Distributions in the Powder Flame Spray Process

Powder flame spray is a flexible, straightforward process. Particulate feed stock is heated and accelerated using an oxy-fuel flame. Liquid feed stock droplets impact the substrate, deform, and solidify to form a coating. Like other spray processes, coating microstructure and properties are directly related to particle velocity and temperature at the time of impact. Many controllable process inputs affect particle temperature and particle velocity. Data, from a series of designed experiments, exploring these factors and quantifying their significance are reviewed. These data show that multiple process inputs, especially torch hardware, can significantly affect particle temperature and velocity distributions in the powder flame spray process.     

Improving the Generalization Ability of an Artificial Neural Network in Predicting In-Flight Particle Characteristics of an Atmospheric Plasma Spray Process

This paper presents the application of the artificial neural network into an atmospheric plasma spray process for predicting the in-flight particle characteristics, which have significant influence on the in-service coating properties. One of the major problems for such function-approximating neural network is over-fitting, which reduces the generalization capability of a trained network and its ability to work with sufficient accuracy under a new environment. Two methods are used to analyze the improvement in the network’s generalization ability: (i) cross-validation and early stopping, and (ii) Bayesian regularization. Simulations are performed both on the original and expanded database with different training conditions to obtain the variations in performance of the trained networks under various environments. The study further illustrates the design and optimization procedures and analyzes the predicted values, with respect to the experimental ones, to evaluate the performance and generalization ability of the network. The simulation results show that the performance of the trained networks with regularization is improved over that with cross-validation and early stopping and, furthermore, the generalization capability of the networks is improved; thus preventing any phenomenon associated with over-fitting.     

Velocity and Temperature of In-Flight Particles and Its Significance in Determining the Microstructure and Mechanical Properties of TBCs

The correlation between particle in-flight parameter, defect content and mechanical property of yttria-stabilized zirconia coating was systematically studied in the present work. The melting state of in-flight particle during spraying was simulated using computational fluid dynamics. The results suggested that, with the increase of velocity and temperature of in-flight particles in the plasma jet, the particles changed from partially melted state to fully melted one. As a result, the total defect content of as-sprayed coating gradually decreased, while elastic modulus and microhardness increased correspondingly. However, the fracture toughness of as-sprayed coating reached a maximum value when the total defect content reached approximately 9.1%.     

激光熔覆熔池图像检测研究

针对激光熔覆系统建立了熔池图像采集系统,并对采集的熔池图像进行处理,获得了熔池的面积。利用该检测系统研究了不同激光功率、扫描速度、送粉率条件下的熔池图像变化规律。同时,研究了不同工艺参数条件下,熔池图像与熔覆质量之间的关系。     

Investigation into High-Temperature Interfacial Strength of Heat-Resisting Alloy Deposited by Laser Melting Process

Metals and Materials International - This paper presents an investigation of the interfacial strength between a material deposited on a substrate via direct energy deposition (DED) process. Using...     

Effect of the Process Parameters on the Indentation Size of Particle Deposited Using Supersonic Laser Deposition

利用有限元分析软件ANSYS Multiphysics/LS-DYNA模块,模拟了超音速激光沉积工艺在中碳钢基体上沉积Stellite 6合金颗粒的过程,分析了颗粒尺寸、温度及基体温度对颗粒沉积的变形行为、沉积处凹坑深度、宽度的影响。通过提取沉积处单元体的坐标变化值,获得了颗粒碰撞基体后的凹坑深度和宽度的数值,并通过计算得颗粒能有效沉积的宽深比范围,并对这些数值进行分析和数值拟合。结果表明:颗粒能有效沉积的宽深比值范围在1.3~1.5。     

Particle Size Distribution of the Filling Powder in Cored Wires: Its Effect on Arc Behavior, In-Flight Particle Behavior, and Splat Formation

The filling powder, as a part of the feedstock in cored wires, directly influences the particle formation, in-flight particle behavior, the coating microstructure, and consequently the behavior of the desired coating, produced by twin wire arc spraying (TWAS). In this work, the effect of the particle size distribution of the filling powder in cored wires was studied. The process parameters were changed for different intervals of particle size distributions. Arc fluctuations were measured and found to be higher at smaller particle sizes. The in-flight particles showed a higher velocity when powders with smaller grain sizes were used and higher particle temperature when bigger grain sizes were used. The splats tended to form a regular disk shape in the case of smaller grain sizes. This investigation studied the important effect of using cored wires and the filling powders grain sizes on the TWAS process.     

65Mn钢在热处理过程中硬度及其参数优化研究

研究65Mn弹簧钢在不同热处理条件下的硬度,利用数学模型建立试验钢硬度与热处理性能的关系,优化热处理参数。结果表明,随着回火温度的增加,试验钢硬度下降;延长奥氏体化时间,其硬度先增加后缓慢下降;当淬火加热温度为851.5℃,时间为18.5 min,回火温度为147.0℃,试验钢硬度最大。     

送粉激光熔覆工艺参数与熔覆层参数间的关系

从理论上推导出熔覆层参数与激光熔覆工艺参数间的关系式。论述了关于激光热有效利用率β、稀释率η的实验检测方法,并在给定激光功率Ｐ、扫描速度Ｖ、光斑直径ｄ下,通过调整送粉率Ｖｆ获得不同厚度的熔覆层,实际检测与计算理论值进行比较,两者吻合得很好。为分析问题方便,提出了能够反映熔覆层界面真实状况的真实稀释率η的概念。     

CSP薄板坯连铸开浇炉次大型夹杂物研究与控制

某钢厂CSP薄板连铸生产高强汽车用钢、家电用钢等产品,开浇炉次卷板表面大型夹杂缺陷对产品质量造成严重危害,通过在中间包取样,采用扫描电镜、氧氮分析、光谱分析等手段,结合现场工艺参数,对产生夹杂缺陷的影响因素进行了分析研究。结果表明,造成CSP薄板坯开浇过程结晶器液面波动的主要原因为钢液二次氧化生成大量的夹杂物,以及钢液钙铝比控制不合理,造成钢液流动性变差。基于研究结果提出了相应的控制措施,开机炉次大型夹杂缺陷率降低了35.82%。     

Numerical and Experimental Investigation of Residual Stress in Thermal Barrier Coatings During APS Process

Thermal barrier coating (TBC) system is widely used in modern gas turbines to protect the internals and enable them to service in higher temperature environment. Residual stress in the TBC system can be induced during its production procedure, such as air plasma spraying (APS) process, and affect its performance to a large extent. The temperature history and the evolution of residual stress in the TBC system during APS process were studied in this paper by finite element simulation and hole-drilling experiment. A five-layered TBC specimen model was established, and a thermo-mechanical-coupled analysis was conducted in the simulation. The “modified element birth-death technique” was used to represent the formation of TBC. In addition, experimental validation of the simulation result was carried out on a TBC specimen using hole-drilling technique combined with moiré interferometry. The experimental data agreed well with the simulation results and the study of this paper could provide a reference for the production of the TBC system.     

Supervision and Measuring of Particle Parameters During the Wire-Arc Spraying Process with the Diagnostic Systems Accuraspray-g3 and LDA (Laser-Doppler-Anemometry)

Due to low cost of operation, high deposition rates and efficiency, wire arc spraying has become one of the most important thermal spray technologies, especially as a tool for coatings used to improve corrosion and wear protection. In order to obtain high-quality coatings, the flow characteristics of the atomizing gas have to be optimized. Thus, the nozzle design as well as the properties of the gas used need to be adjusted and the resulting particle parameters have to be quantified. Employing the Accuraspray-g3 system in combination with Laser Doppler Anemometry (LDA), the particle size distribution and velocity have been measured for a wide range of parameters, including different materials, different gas pressures and nozzles resulting in design suggestions and offering the possibility to compare the two different diagnostic systems.     

激光变质处理ZL108铝合金的组织与性能

采用激光熔凝处理ZL108合金，合金组织得到明显细化，硬度也显著提高，改善了ZL108合金的摩擦磨损性能。同时，对熔凝区的强化机理进行了探讨。     

锡青铜激光选区熔化工艺及其性能研究

为了研究QSn6.5-0.1锡青铜激光选区熔化(SLM)技术直接成型工艺及其成型性能,设计三因素四水平正交工艺实验,研究激光功率、扫描速度和扫描间距对致密度的影响,采用SEM、OM、Micro-CT以及显微硬度仪研究微观组织与硬度。结果表明:选择合理的优化工艺参数,锡青铜(SLM)成型致密度最高达到98.71%;微观组织为网络状枝晶结构且分布均匀的(α+δ)相和α相;成型试样显微维氏硬度比传统铸造的软态(700～900 MPa)高45%左右;直接成型的风轮模型致密性高。表明采用激光选区熔化技术可以成型性能较好的QSn6.5-0.1锡青铜合金零件。     

Ni基合金激光熔覆层组织特征及凝固过程的研究

采用自动送粉方法,在４５钢表面激光熔覆Ｎｉ基合金粉末,较为系统地研究了扫描速度对激光熔覆层显微组织特征的影响。实验结果表明：Ｎｉ基合金粉末激光熔覆层显微组织由枝晶及块状（或针状）共晶组织构成,共晶碳化物的形态由化学成分确定;结合界面不存在白亮带,为细小亚共晶组织;离结合界面距离的增加,熔覆层组织逐渐变细,显微组织表现出明显不均匀性,提高激光扫描速度,明显细化了组织邮组织显微硬度。改善了熔覆层局部组     

AlSi7Mg合金选区激光熔化工艺及性能研究

为了研究Al Si7Mg合金选区激光熔化成形工艺及性能,通过改变激光功率和扫描速度,得到不同工艺参数对成形试样性能的影响规律。结果表明:试样的相对密度随激光功率和扫描速度的增大均呈先上升后下降的趋势,试样的相对密度最高可达99.95%;随激光功率的增加,试样的拉伸性能先上升后下降;激光功率为350 W、扫描速度1 400 mm/s时,试样抗拉强度为423 MPa,屈服强度为293 MPa。     

铸铁件EPC—V法工艺因素对充型速度的影响

通过正交试验研究了铸铁件负压气化模铸造充型过程中各种工艺因素对金属液充型速度的影响。试验结果表明，在考虑的工艺因素中，对充型速度的影响由大到小依次为：模样材料、金属静压头、涂料透气性和浇注温度。模样材料与涂料的交互作用对金属液的充型速度具有非常重要的作用。