不同预热温度WC增强镍基合金堆焊层的微结构演化与摩擦学性能

目的 研究不同预热温度(200、400 ℃)条件下硬质颗粒增强镍基合金堆焊层的微观组织结构演化机理,以及对其力学性能、磨损性能的影响规律。方法 采用等离子弧焊接技术在42CrMo钢基体表面堆焊硬质WC颗粒增强镍基强化层,利用X射线衍射(XRD)、扫描电子显微镜(SEM)、硬度计和摩擦磨损试验机,分析不同预热温度堆焊层的物相组成、微观组织形貌、力学性能和磨损性能,建立堆焊层制备工艺–微观组织结构–力学性能–磨损性能之间的强映射关系。结果 堆焊层主要由γ-Ni/Fe、WC、W2C、M7C3、M23C6、Ni2W4C、Cr3C2等物相组成,在预热温度200 ℃下堆焊层二次碳化物析出较少,发生了严重的WC颗粒沉降现象;在预热温度400 ℃下,堆焊层析出了大量的二次碳化物,WC颗粒沉降减弱,组织均匀性提高。在400 ℃下预热,相较于200 ℃下预热,堆焊层的磨损质量减少了51.85%,磨损率减少了51.89%。结论 高预热温度和长保温时间可促进WC颗粒界面反应,驱动大面积二次碳化物的析出,有效缓解WC颗粒沉降,改善凝固组织中WC颗粒的分布均匀性,从而显著提高堆焊层的硬度和耐磨性。     

TiC添加量对高能激光熔覆Inconel718基陶瓷涂层显微组织和摩擦磨损性能的影响

目的 针对Inconel718镍基高温合金耐磨性不足的问题,制备小尺度TiC增强Inconel718镍基高温合金耐磨复合材料,提升其硬度及耐磨性.方法 利用4000 W高能激光束快速熔融制备TiC/Inconel718基陶瓷复合涂层,并针对TiC质量分数分别为5％、15％、25％的复合涂层,依次进行物相成分、显微组织、压痕硬度、摩擦磨损性能等方面的分析.结果 随着TiC含量的增加,γ-(Ni,Cr,Fe)基体上析出的TiC小尺度颗粒逐渐增多,显微组织明显细化,TiC晶界处偏聚了大量Nb、Mo元素,并与Ti元素置换生成了铌、钼类碳化物.同时,(Nb,Ti)C复合型碳化物和Laves相的析出,进一步提升了复合涂层的显微硬度,由297 HV0.2逐步提升至408 HV0.2,摩擦系数从0.3402降低至0.2628,磨损率从35.15×10–4 g/(N·m)减少至5.96×10–4 g/(N·m),磨损机制由严重的粘着磨损转变为以磨粒磨损和氧化磨损为主.结论 通过高能激光熔覆制备小尺度TiC增强体颗粒,可细化复合涂层的显微组织,其显微硬度随TiC含量的增加而相应提高.在磨损试验过程中,TiC/Inconel718陶瓷复合涂层表现出良好的减摩和耐磨性能.     

WC-Ni-Fe-Mo硬质合金的微观结构与性能研究

本文采用低压烧结的方式制备了性能良好的 WC–Ni–Fe–Mo 硬质合金,研究分析了不同 Mo 添加量对 WC–Ni–Fe硬质合金组织性能的影响。结果表明：不同 Mo 添加量对 WC–Ni–Fe 硬质合金的微观结构与性能有着显著地影响。添加微量的 Mo 可以抑制 WC-Ni-Fe 硬质合金中 WC 晶粒的溶解再析出长大,一定程度上可以细化 WC 晶粒。随着 Mo 在 WC–Ni–Fe 合金中的含量增加,合金孔隙率逐渐下降。密度先下降后升高,而抗弯强度的变化趋势则相反。当 Mo 添加量较少时,合金的硬度较为稳定,抗弯强度明显提升,而断裂韧性逐渐降低;当 Mo 添加量较大时,合金的硬度、抗弯强度降低,而断裂韧性上升。当 Mo 的添加量为0.5 wt %时,合金具有最佳的力学性能,可与同比例 Co 含量的 WC–Co 硬质合金相媲美,其维氏硬度为 HV 1460、抗弯强度为 4245 MPa、断裂韧性为 17.01 MPa·m1/2。     

铸钢0Cr13Ni5Mo表面电火花沉积YG8涂层的组织和性能

采用新型电火花设备在铸钢表面制备了YG8涂层,采用SEM、XRD技术研究其微观组织和耐磨性能。结果表明:沉积层主要由Co3W3C、Fe3W3C、Fe3Mo3C、WC1 x和Fe7W6C等相组成;沉积层与基体冶金结合,细晶碳化物相弥散分布在沉积层中,能提高沉积层的硬度,平均硬度为1 896.8HV,比基体硬度提高了5倍;沉积层磨损性能是基体的3.4倍,沉积层磨损机理主要是粘着磨损、颗粒磨损和氧化磨损的综合作用;沉积时骤热骤冷过程中形成的细晶粒硬质相是提高沉积层硬度和耐磨性的主要因素。     

等离子熔化沉积TiC增强Inconel 718基原位自生复合材料显微组织及高温耐磨性

为改善镍基高温合金Inconel 718的高温耐磨性,利用同轴送粉等离子熔化沉积快速成形技术原位合成了TiC增强Inconel 718高温合金基高温耐磨复合材料。分析了复合材料的显微组织结构和原位自生过程,探讨了增强相TiC的含量对复合材料的显微硬度及高温干滑动摩擦磨损性能的影响规律,研究了复合材料的高温磨损机理。结果表明:复合材料组织细小致密,显微硬度随TiC增强相体积分数增加而相应提高;在高温干滑动磨损实验条件下,复合材料表现出优异的耐磨性。     

感应熔覆铁基合金涂层的显微组织与性能

采用感应熔覆技术在奥氏体不锈钢1Cr18Ni9Ti基体上制备了Fe基合金涂层。利用带有能谱仪的场发射扫描电镜(FESEM)分析了熔覆层的显微组织形貌和元素组成,使用X射线衍射仪分析了涂层的物相组成,采用差热分析仪对合金粉末进行了热分析,用显微硬度计和摩擦磨损试验机测试了涂层的显微硬度及干摩擦条件下的滑动磨损性能。结果表明,感应熔覆铁基合金涂层组织致密,内部和界面无孔隙,涂层与基体形成了良好的冶金结合;涂层主要由α-Fe、(Cr,Fe)_7C_3、Cr_7C_3、Ni_3Fe和Fe_3C等组成,且α-Fe中均匀分布颗粒细小的(Cr,Fe)_7C_3、Cr_7C_3析出相;涂层显微硬度约为250HV_(0.1);在不同载荷下,感应熔覆Fe基合金涂层的耐磨损性能均优于1Cr18Ni9Ti基体,涂层磨损机理为典型的层状剥落和粘着磨损。     

直接激光沉积Ti6Al4V/Inconel 718复合材料微观组织与力学性能分析

Ti6Al4V和Inconel 718合金被广泛用于航空航天。但TC4或Inconel 718难以同时满足轻量化和耐高温的需求。本文采用直接激光沉积制备了不同比例Ti6Al4V / Inconel 718复合材料。分别通过X射线衍射,扫描电子显微镜和能谱仪分析相组成,微观结构和元素分布。同时,研究了显微硬度和摩擦磨损性能。研究表明：随着Inconel 718的比例增加,有Ti2Ni和Ni3Ti金属间化合物形成。Ti2Ni的形成机理为：β→α+ Ti2Ni和L→β-Ti+ Ti2Ni,且Ti2Ni金属间化合物的偏析机理为晶间偏析。随着Inconel 718含量增加,复合材料的显微硬度逐渐增加。当Inconel 718的体积分数为50％时,其平均显微硬度值为770 HV,比100％ Ti6Al4V的平均显微硬度高85.5％。显微硬度增加与Ti2Ni金属间化合物的析出强化直接相关。复合材料以磨料磨损为主,并伴随着黏着磨损。随着Inconel 718的增加,黏着磨损减弱。当Inconel 718的体积分数达到达到50％时,磨损量仅为100％ Ti6Al4V的36.9％。     

铸造碳化钨添加量对镍基复合喷熔涂层性能的影响

在镍基合金粉末NiCrBSi中添加不同比例的铸造碳化钨(WC),并采用氧乙炔火焰喷熔工艺在低碳钢表面制备了相应的Ni基WC复合涂层.采用金相显微镜观察了涂层的显微组织,采用湿砂橡胶轮式磨粒磨损试验机测试了涂层的抗磨粒磨损性能,并采用扫描电镜观察了喷熔粉末和喷熔层磨损后的形貌.结果表明:喷熔层的组织为在NiCr合金基体上弥散分布着不同粒度的碳(硼)化物硬质相;涂层的显微组织和WC的含量对Ni基WC喷熔层的硬度和抗磨损性能影响很大,涂层的硬度和抗磨损性能随WC添加量的增加先增加后减小;当WC的含量为35％时,Ni基体WC喷熔涂层的硬度最高,相应的抗磨粒磨损性能最好.     

时效处理对WC/Cu-Ni-Mn堆焊层耐磨损性能影响

通过对比未时效与时效后WC/Cu-Ni-Mn堆焊层的微观组织、界面及耐磨损性能,研究时效处理对其耐磨损性能的影响规律,并揭示其耐磨损机理. 结果表明,未时效和时效后的WC/Cu-Ni-Mn涂层相对耐磨损性能分别是时效后Cu-Ni-Mn基体的170.72和210.77倍,时效后涂层耐磨性能提升了23.5%;时效处理后Cu-Ni-Mn金属基中析出了NiMn第二相,基体硬度提升了2.3倍,从而为WC颗粒增强相提供了更稳定支撑;而未时效的Cu-Ni-Mn合金中Ni,Mn原子固溶到Cu晶格,形成了一种α-Cu固溶体;未时效和时效后WC/Cu-Ni-Mn的主要磨损机理均为磨粒磨损和黏着磨损.     

直接激光沉积Ti6Al4V/Inconel 718复合材料微观组织与力学性能分析（英文）

Ti6Al4V和Inconel 718合金被广泛用于航空航天。但TC4或Inconel 718难以同时满足轻量化和耐高温的需求。因此采用直接激光沉积制备了不同比例Ti6Al4V/Inconel 718复合材料。分别通过X射线衍射,扫描电子显微镜和能谱仪分析相组成,微观结构和元素分布。同时,研究了显微硬度和摩擦磨损性能。结果表明:随着Inconel 718的比例增加,有Ti_2Ni和Ni_3Ti金属间化合物形成。Ti_2Ni的形成机理为:β→α+Ti_2Ni和L→β-Ti+Ti_2Ni,且Ti_2Ni金属间化合物的偏析机理为晶间偏析。随着Inconel 718含量增加,复合材料的显微硬度逐渐增加。当Inconel718的体积分数为50%时,其平均显微硬度值为7700MPa,比100%Ti6Al4V的平均显微硬度高85.5%。显微硬度增加与Ti_2Ni金属间化合物的析出强化直接相关。复合材料以磨料磨损为主,并伴随着黏着磨损。随着Inconel 718的增加,黏着磨损减弱。当Inconel 718的体积分数达到50%时,磨损量仅为100%Ti6Al4V的36.9%。     

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).     

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.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

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.