AC-HVAF喷涂Ni60/WC复合涂层组织及性能研究

利用活性燃烧高速燃气(AC-HAVF)喷涂技术在0Cr13Ni5Mo不锈钢上制备了Ni60/WC复合涂层,研究了其微观组织及耐磨耐蚀性能.结果表明:涂层主要由Fe-Ni固溶体以及Cr0.19Fe0.7Ni0.11,WC,M6C(Ni2W4C或Fe3W3C),Cr26C3,CrB2等相组成;涂层与基体结合很好,涂层的孔隙率约为2.5%;WC,M6C,Cr26G3,CrB2等硬质相弥散分布于涂层中,部分区域硬质相达到了200～800 nm;涂层硬度分布不均匀,平均硬度为685HV;涂层具有优异的耐磨耐蚀性,其磨损体积是0Cr13Ni5Mo不锈钢的1/8.8,平均腐蚀速度是0Cr13Ni5Mo不锈钢的1/2;涂层的磨损机理以疲劳磨损为主,弥散分布的硬质相是涂层硬度以及耐磨性提高的主要因素.     

基材硬度和涂层厚度对AlCrN多元复合纳米硬质涂层硬度的影响

采用真空阴极多弧离子镀技术制备了Al Cr N多元复合纳米硬质涂层,利用洛氏硬度计、划痕仪、HV显微硬度计、球磨仪、扫描电子显微镜、能谱仪及X射线衍射仪检测并分析了涂层膜基结合力、显微形貌、相结构以及基体硬度、涂层厚度对涂层硬度的影响。结果表明,涂层以Al Cr N/Cr N结构沉积,随着涂层厚度的增加,膜基结合强度提高。涂层表面成波纹状,有少量大颗粒,涂层内部呈Na Cl结构,含有大量呈柱状形式生长的面心立方的c-Cr N相和c-Al N相,择优取向均为(200)。同等基体硬度时,涂层厚度的增加有利于涂层硬度的提高,最佳涂层厚度为3.5~5.0μm。同等涂层厚度时,涂层硬度随着基体硬度的增加而增加,当涂层厚度低于4.0μm,基材硬度是影响涂层塑性变形抗力的主要因素。     

4Cr13钢基表面SiC/Ta复合涂层的制备及摩擦磨损性能

针对马氏体不锈钢的表面耐磨性不能满足应用需求,且在钢基表面直接制备Si C涂层会产生与基体结合不良的问题,采用双辉等离子表面冶金技术在4Cr13马氏体不锈钢表面制备SiC/Ta复合涂层,对涂层的组织结构、表面硬度、结合强度和摩擦磨损性能进行研究。结果表明,所制备的SiC/Ta复合涂层厚5~6μm,由SiC、Ta、Ta_2C和TaC相构成。SiC/Ta/基体各层间以扩散连接,与基体结合良好。经双辉等离子表面冶金技术处理后,表面显微硬度由基材的279 HV_(0.2)提高到1 738 HV_(0.2)。4Cr13不锈钢的摩擦学性能也得到明显改善,摩擦因数比基材的平均摩擦因数降低了0.32,磨损率是基材磨损率的4%。     

ZG06Cr13Ni4Mo不锈钢超音速火焰喷涂WC-10Co-4Cr涂层的抗磨蚀性能

采用超音速火焰(HVOF)热喷涂工艺,在ZG06Cr13Ni4Mo不锈钢上制备了纳米WC-10Co-4Cr涂层。利用压痕法和灰度法分别测试了涂层的显微硬度和孔隙率,并利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、电子万能试验机和磨蚀试验机分别对涂层的相结构、表面形貌、结合强度和抗磨蚀性能进行了分析和测试。结果表明,获得的WC-10Co-4Cr涂层的平均显微硬度和结合强度高,分别达到1 435HV0.2和70.4 MPa,组织结构致密。相对于ZG06Cr13Ni54Mo不锈钢,纳米WC-10Co-4Cr涂层具有优异的抗磨蚀性能,其抗磨蚀性能是ZG06Cr13Ni54Mo不锈钢的10倍以上。     

热处理对Cr/Al复合镀层组织转变的影响

通过先在水溶液中电镀Cr之后再在摩尔比为2∶1的AlCl3-EMIC(氯化1-甲基3-乙基咪唑)离子液体电镀Al的方法,在1Cr17钢表面制备出Cr/Al复合镀层。研究了在740℃条件下不同时间热处理对涂层组织和结构的影响。光学显微镜、二次电子和特征X射线能谱及X射线衍射研究结果表明:Cr/Al复合镀层通过740℃热处理可以得到Al-Cr涂层,随着时间的延长,外表面合金层成分依次按Al4Cr→Al11Cr4→Al9Cr4→Al8Cr5变化,最后形成单相的Al8Cr5,且涂层与基体之间不发生明显的互扩散;在5～20 min内Al9Cr4成分层的厚度及反应掉的Cr镀层厚度与时间平方根符合线性关系;氮气气氛中热处理可以减少涂层表面的空洞。显微硬度测试结果表明:Al8Cr5的脆性小,且硬度高于其他3种合金层。     

超音速火焰喷涂Fe-Cr-Ni基涂层的组织与性能研究

采用多元Fe-Cr-Ni基合金(含Si、Co、B、Cu等)为喷涂粉末在不锈钢基体表面,用超音速火焰(HVOF)喷涂法制备厚度达200 μm的涂层.采用金相显微镜、扫描电镜、X射线衍射仪对涂层的组织及相组成进行了研究,用显微硬度计和磁致伸缩汽蚀仪对涂层的性能进行了测试.结果表明,该涂层致密,颗粒分布均匀,其显微硬度是基体的5倍,达到1050 HV0.1,靠近涂层的基体表面发生了加工硬化.涂层的抗汽蚀性明显优于ZG06Cr13Ni5Mo不锈钢,前者的质量损失约为后者的1/3.     

预热方式对3Cr13不锈钢氮碳氧复合渗层厚度及性能的影响

经淬火、回火处理后,对3Cr13不锈钢进行氮碳氧复合渗可提高其硬度和耐蚀性,研究了不同预热方式对该钢复合渗层硬度和耐蚀性的影响。结果表明：不预热直接进行氮碳氧复合处理后,3Cr13不锈钢渗层薄,且不均匀;经400 ℃空气炉中预热及氧化盐浴中预热后,渗层厚度较厚,且均匀。3Cr13不锈钢经复合处理后表层硬度大幅提高,400 ℃空气炉中及氧化盐浴中预热试样表层（距表面距离≤45 μm）硬度比不预热试样硬度高100～150 HV0.1。3Cr13不锈钢复合渗层耐蚀性由高到低为：400 ℃空气炉中预热、400 ℃氧化盐浴中预热、不预热。     

前驱体对激光熔覆复合溶胶凝胶制备陶瓷涂层的影响

目的研究不同前驱体配比下,激光熔覆复合溶胶凝胶在3Cr13不锈钢表面制备的陶瓷涂层的性能,并对强化机理进行分析。方法通过溶胶凝胶法制备均匀的前驱体,即Ti O2和C(微米石墨和碳纳米管),利用激光熔覆技术,在3Cr13不锈钢基体表面制备出高性能的涂层。采用光学显微镜、X射线衍射仪、扫描电镜和能谱仪对涂层组织和相成分进行分析,采用维氏硬度计对涂层的硬度进行测试,采用HT-600型高温摩擦磨损试验机测试基体和熔覆层在常温下的磨损性能。结果通过溶胶凝胶法,制备出均匀的Ti O2和C混合粉末。激光熔覆后,在覆层中均匀分布着Ti C和Cr7C3强化相。改变前驱体配比,当C和Ti O2的摩尔比增大时,涂层组织明显细化,且涂层中无气孔,显微硬度也有较大提高。当n(TiO2)∶n(C)=1∶8时,次表面显微硬度达到810HV0.2,涂层硬度从上到下呈现递减的趋势,且涂层的耐磨性最好,为基体的4.5倍。结论增大C和Ti O2两者摩尔比,可以提高熔覆层的显微硬度和耐磨性。在熔池中,Ti C密度较小,涂层中硬质颗粒从上到下依次减少,与之对应,硬度也依次递减。同时,碳纳米管的加入将对涂层起到细晶强化的效果。Ti与碳纳米管和微米石墨结合生成微米级和亚微米级Ti C,提高了形核率,Cr7C3以亚微米级Ti C为非均质核心,形核长大,生成均匀分布的Cr7C3强化相。     

超音速火焰喷涂Fe-Cr基涂层的硬度与汽蚀性

采用超音速火焰(HVOF)喷涂技术在1Cr18Ni9Ti不锈钢表面制备了Fe-Cr基涂层,用磁致伸缩汽蚀仪研究了喷涂层的汽蚀性,并与水利机械常用材料ZG06Cr13Ni5Mo马氏体不锈钢进行了对比。结果表明:涂层包含未熔或半熔的球形颗粒和少量孔隙,层与层之间结合紧密,层间无明显条带状组织。Fe-Cr涂层具有高的硬度(1099HV0.2),抗汽蚀性明显优于ZG06Cr13Ni5Mo马氏体不锈钢(285HV0.2)。两者的汽蚀形貌存在较大差异,ZG06Cr13Ni5Mo马氏体不锈钢的汽蚀坑圆滑,而Fe-Cr基涂层汽蚀坑形状极不规则,与涂层中的孔隙有某种对应关系。     

等离子喷涂Al_2O_3(13%TiO_2)涂层和NiCr-Cr_3C_2涂层的组织性能研究

通过等离子喷涂方法在穿孔顶头尾部材料42CrMo钢表面分别制备NiCr-Cr3C2涂层和Al2O3(13%TiO2)涂层,运用OM,XRD,SEM等分析测试手段对涂层的组织、形貌和物相成分进行表征,并对两种涂层进行了显微硬度及抗热震性能实验.结果表明:喷涂涂层为典型的层状结构,涂层与基体为机械结合.Al2O3(13%TiO2)涂层以亚稳相γ-Al2O3相为主要相,同时存在α-Al2O3相.喷涂形成NiCr-Cr3C2涂层后物相成分为Cr23C6、Cr7C3、Cr3C2等Cr的碳化物.NiCr-Cr3C2涂层和Al2O3(13%TiO2)涂层的表面平均显微硬度分别为586.4HV,和557.7HV.其平均热震循环次数分别为25次和18次.     

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.