等离子弧喷焊镍基合金对喷焊层硬度的影响

以提高基体材料喷焊层的硬度及耐磨性为目的,使用等离子弧喷焊技术对基体材料(Q345C低合金钢)进行焊接,对于DG.Ni60B镍基合金粉末,选用100,150 A转移弧电流对其进行喷焊。而对于DG.Ni60WC25镍基合金粉末,则在100,150,170,200 A转移弧电流下进行喷焊。结果表明,当使用同一种镍基合金粉末喷焊时,喷焊层最大硬度值和耐磨性随转移弧电流增大而降低。在相同转移弧电流条件下,添加硬质复合材料(碳化钨,WC)镍基合金粉末DG.Ni60WC25焊层的硬度和耐磨性明显高于未添加硬质复合材料镍基合金粉末DG.Ni60B的焊层。试验得出:等离子弧喷焊时,随着转移弧电流的增大,会使喷焊层表面耐磨性减小。但在DG.Ni60B镍基合金粉末中加入硬质相WC之后,对其复合合金粉末进行喷焊,可使转移弧电流对焊层表面耐磨性的影响程度降低。同时,在喷焊层和基体材料结合界面之间出现较大的硬度值,甚至在界面处可获得硬度的最大值。     

[例10]等离子喷焊技术应用于新阀门制造和旧阀门再制造

粉末等离子喷焊是利用压缩等离子弧产生的高温熔化金属粉末,在工件表面形成一层与基体冶金结合的、具有特定性能熔敷层的表面堆焊技术.     

表面工程应用实例 [例10]等离子喷焊技术应用于新阀门制造和旧阀门再制造

粉末等离子喷焊是利用压缩等离子弧产生的高温熔化金属粉末,在工件表面形成一层与基体冶金结合的、具有特定性能熔敷层的表面堆焊技术.     

玻璃模具型腔等离子弧喷焊工艺试验

采用等离子弧喷焊工艺方法,选用镍基合金粉末在玻璃模具型腔的关键部位进行了等离子弧喷焊工艺试验,对喷焊层金属的显微组织进行了分析,测试了喷焊层的显微硬度.试验结果表明,喷焊层与基体为冶金结合,喷焊层呈枝状晶组织,硬度达到HV296.通过对玻璃模具型腔进行等离子弧喷焊镍基合金,玻璃模具的耐磨性、抗高温氧化性能得到显著提高,其使用寿命也得到延长.     

等离子弧喷焊铜基合金的组织和耐磨性

采用等离子弧喷焊技术，在Q235钢表面制成熔敷低磷锡青铜和镍基合金混合粉末的喷焊层。利用金相、扫描电镜(SEM)和X射线衍射(XRD)等方法对喷焊层和结合层的组织进行研究，同时测试了喷焊层的硬度和耐磨性。结果表明，喷焊层与基体是冶金结合，结合线清晰。熔敷合金稀释率低。喷焊材料为铜基合金DGCul50时，喷焊层含有α—Cu相，δ相，ε相和Cu3P。喷焊材料为铜基合金DGCul50 适量镍基合金DGNi50A时喷焊层主要含有α—Cu相，δ相，ε相，Cu3P，γ—Ni，Ni2B，CrB，(Fe，Ni)23C6，(Cu，Ni)23C6和Fe5Si2B2。随加入铜基合金粉末中的镍基合金粉末量的增加，喷焊层与基体之间的结合层加厚，喷焊层的硬度和耐磨性显著提高。     

偏心内孔零件自动化等离子弧粉末堆焊修复系统

将数字化控制技术和精密脉冲等离子粉末堆焊技术相结合,采用四轴联动旋转设计,研制了偏心内孔零件自动化等离子弧粉末堆焊修复系统。该系统由精密脉冲等离子弧粉末堆焊熔覆系统、设备控制与运行监测系统、堆焊枪x、y、z三轴行走机构及偏心零件主体支撑机构组成。使用该堆焊修复系统,利用铁基自熔合金粉末对废旧典型偏心零件过电缆封隔器的偏心孔内表面进行了堆焊修复验证试验,制备了堆焊修复层试样,借助先进的材料分析技术分别测定了修复层的表面形貌、显微组织、显微硬度、表面残余应力和切削加工性。结果表明,该系统实现了偏心零件快速、精准、高效的堆焊修复,修复层均匀平整,与基体属于冶金结合,过渡区域缺陷少,堆焊质量良好,加工性能满足使用要求,解决了偏心零件堆焊修复定位难度大、操作工艺复杂的难题,具有广阔的应用前景。     

等离子弧粉末喷焊内表面技术的研究

设计并研制了深内孔等离子弧粉末喷焊枪，该枪具有在高温下连续稳定工作的优异性能。论述了内孔喷焊装置的设计原则，并提出了两种规格机筒喷焊的最佳规范。     

等离子喷焊低温马氏体相变合金粉末的组织与性能

为减小喷焊过程中热收缩形成的拉伸应力,采用等离子喷焊的方法,在Q235钢基体上进行堆焊,制备出具有残余压缩应力的低温马氏体相变合金耐磨复合涂层。利用金相显微镜(OM)、SEM、EDS、XRD、X射线残余应力测试仪、显微硬度仪和摩擦磨损试验机等,对喷焊层金属的微观组织、成分和力学性能进行了分析和研究。结果表明:合适的工艺参数下,能够得到与基体呈冶金结合的无缺陷喷焊层组织;喷焊层的组织主要为马氏体和少量残余奥氏体组成;喷焊层获得较为理想的残余压缩应力,最大残余压缩应力可达到-351.2 MPa,平均残余奥氏体的质量分数约为10.18%;和基体材料相比较,等离子喷焊层的硬度提高2.5倍,耐磨性提高47.22倍。     

等离子喷焊工艺研究

采用正交试验方法对Ｆｅ０７、Ｆｅ９Ａｔ等铁基合金粉末的等离子喷焊工艺参数进行了研究，并找出了最优值。对铁基合金粉末的喷焊层组织与性能进行了金相分析、硬度试验以及电子探针测量基体与喷焊层界面的合金元素分布。本文对于提高等离子喷焊质量及探讨喷焊层的强化机理具有理论与实际意义。     

Cu14Al4.5FeNiCe等离子喷焊层组织及摩擦学特性

气雾水冷方法制备Cu14Al4.5FeNiCe合金粉末,等离子喷焊方法实现粉末在45钢表面喷焊层的制备.采用光学显微镜,XRD,SEM,EDS分析喷焊层表面、结合横断截面、磨损表面及合金相结构和组织形貌,拉伸法测定喷焊层与基体结合力,用UMT-2MT摩擦试验机测试喷焊层与304不锈钢对摩的无润滑摩擦磨损行为.结果表明,...     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.