Effects of heating temperature on interfacial microstructure and compressive strength of brazed CBN-AlN composite abrasive grits

CBN-AlN composite abrasive grits and AISI 1045 steel were brazed using Ag-Cu-Ti active filler alloy by heating up to the temperature of 890,900 and 920 ℃,respectively,and then held at the temperature for 8 min.Optical microscope,scanning electron microscope and X-ray diffraction equipment were utilized to study the effects of heating temperature on the microstructure of the joining interface.The compressive strength of the brazed composite grits was also measured.The experimental results show that the atoms of Ti,Al,B and N have preferentially penetrated towards the joining interface of composite grits and filler alloy.The compounds of Ti-nitride,Ti-borides and Ti3AlN were formed in the reaction layer.Degradation effect was not made on the compressive strength of the CBN-AlN composite grits when the brazing process was carried out in the temperature range of 890-920 ℃.     

Influence of TiX (<Emphasis Type="Italic">X</Emphasis>=B<Subscript>2</Subscript> or N) addition on the interfacial microstructure features of CBN grains and AgCuTi composite filler

Joining experiments of CBN grains to AISI 1045 steel were conducted using Ag-Cu-Ti composite fillers containing TiX (X=B₂ or N) particles at 920 °C for 5 min. The influences of TiB₂ and TiN particles on the interfacial microstructure features between CBN and filler were investigated comparatively. The experimental results show that TiN particles are more effective than TiB₂ ones to control the interfacial reaction and particularly the resultants. Thermodynamic analysis reveals that the varied interfacial reaction induced by the addition of TiB₂ and TiN particles is mainly atttributed to the activity change of the B and Ti elements in the brazing reaction system.     

离子软氮化与离子氧化复合处理

用自行研制的保温式多功能离子热处理炉对 45中碳结构钢进行了离子软氮化与离子氧化复合处理 (Ion(NC +O)复合处理 )。Ion(NC +O)复合渗层是由黑色致密的Fe3O4膜、ε白亮化合物层和γ′扩散层等三部分组成。实验结果显示 ,经Ion(NC +O)双重复合处理后 ,45钢的表面硬度和耐蚀性能都有大幅度的提高。与化学法的QPQ技术相比 ,Ion(NC +O)复合处理技术是一种环境友好的处理技术。     

Microstructure and wear resistance of electro-thermal explosion sprayed stellite coating used for remanufacturing

Electro-thermal explosion directional spraying was used to prepare the stellite coating on substrate of the AISI 1045 steel. The morphologies of cross-section and worn scar, porosity, distribution of elements, microhardness and wear resistance of the coating were determined by means of SEM, EDAX, micro-hardness tester and sliding wear tester. Because of the compact construction, good bonding and high hardness, the coating is characterized by good wear resistance. The results show that the mainly failure mode of the stellite coating is microplowing.     

拉—拉变幅载荷下45钢切口件疲劳寿命的分布及其模拟

根据45钢切口件疲劳寿命表达式中疲劳抗力系数和疲劳门槛值物理意义及概率分布,提出了一种新的模拟45钢切口件变幅载荷下疲劳寿命实验及其分布的方法,并与拉－拉变幅载荷下的实验结果进行了比较,结果表明,45钢切口件在变幅载荷下的疲劳寿命分布的模拟结果服从对数正态分布,并与实验结果符合得很好。     

Significance of experimental data in the design of structures made from 1.4057 steel

This paper presents experimentally-obtained data which can be of importance in the design procedure of engineering components made of 1.4057 （X 17CrNil 6-2; AISI 431） steel. In this manner, uniaxialy tests related to determine material mechanical properties and short-time creep behavior were performed. Based on the mentioned tests, ultimate tensile strength, 0.2 offset yield strength and modulus of elasticity at low and elevated temperatures were determined. Also, creep behavior of considered steel was tested for selected temperatures and selected stress levels. According to experimentally determined Charpy impact energy an assessment of fracture toughness was made.     

Sand-wear resistance of brush electroplated nanocomposite coating in oil and its application to remanufacturing

Sand-wear resistance of nano scale alumina particle reinforced nickel matrix composite coating (n-Al₂O₃/Ni) prepared by brush electroplating technique was investigated via wear tests in sand-contaminated oil lubricant, comparing with that of AISI1045 steel and brush electroplated Ni coating. Effects of testing load, sand content and sand size on worn volume of the three materials, and also coating surface roughness on worn volume of the brush electroplated coatings were accessed. Results show that the worn volume of all the three materials increases with increasing of testing load, sand content and sand size. In the same conditions, n-Al₂O₃/Ni composite coating has the smallest worn volume while AISI1045 steel has the largest because of the n-Al₂O₃ particle effects. As to n-Al₂O₃/Ni and Ni coatings, the surface-polished coatings have obviously lower worn volume than the as-plated coatings. The brush electroplated n-Al₂O₃/Ni composite coating was employed to remanufacture the sand-worn bearing seats of a heavy vehicle and good results were gained. Foundation item: Project (50235030) supported by the National Natural Science Foundation of China; Project (51489020104ZD0401) supported by the National Key Laboratory for Remanufacturing; Project(51418060105JB3058) supported by National Defence Foundation     

Microstructure and wear resistance of electro-thermal explosion sprayed stellite coating used for remanufacturing

Electro-thermal explosion directional spraying was used to prepare the stellite coating on substrate of the AISI 1045 steel. The morphologies of cross-section and worn scar, porosity, distribution of elements, micro-hardness and wear resistance of the coating were determined by means of SEM, EDAX, micro-hardness tester and sliding wear tester. Because of the compact construction, good bonding and high hardness, the coating is characterized by good wear resistance. The results show that the mainly failure mode of the stellite coating is micro-plowing. Foundation item: Project(2003AA331130) supported by Hi-tech Research and Development Program of China; Project(50235030) supported by the National Natural Science Foundation of China     

Numerical analysis of 3D spot continual induction hardening on curved surface of AISI 1045 steel

In order to investigate and predict the material properties of curved surface AISI 1045 steel component during spot continual induction hardening(SCIH),a 3D model for curved surface workpieces which coupled electromagnetic,temperature and phase transformation fields was built by finite element software ANSYS.A small size inductor and magnetizer were used in this model,which can move along the top surface of workpiece flexibly.The effect of inductor moving velocity and workpiece radius on temperature field was analyzed and the heating delay phenomenon was found through comparing the simulated results.The temperature field results indicate that the heating delay phenomenon is more obvious under high inductor moving velocity condition.This trend becomes more obvious if the workpiece radius becomes larger.The predictions of microstructure and micro-hardness distribution were also carried out via this model.The predicted results show that the inductor moving velocity is the dominated factor for the distribution of 100% martensite region and phase transformation region.The influencing factor of workpiece radius on 100% martensite region and phase transformation region distribution is obvious under relatively high inductor moving velocity but inconspicuous under relatively low inductor moving velocity.     

不同C加入量对原位合成TiC颗粒增强钢基表面复合材料组织和性能的影响

为解决金属材料耐磨性与韧性之间的矛盾,以ZG35CrMo为基体,以自蔓延高温合成TiC颗粒为增强体,采用真空消失模铸造工艺制备出表面质量优良的TiC颗粒增强表面耐磨钢基复合材料,对不同C加入量的颗粒增强复合材料的组织和性能进行分析研究.结果表明,制备的表面复合材料分为基体与合金层.当碳粉的加入量为化学计量比4∶1时,复合材料的组织和力学性能较好,加入量过量3∶1时会造成合金层及结合面性能的下降.     

遗传算法在多元铜基钎料成分优化中的应用

ＣｕＺｎ钎料在白口铸铁表面的润湿性能和钎缝剪切强度低于其在钢表面的润湿性能和钎缝剪切强度,白口铸铁向钎料过度溶解所造成的溶蚀是钎料润湿性能差、钎缝剪切强度低的主要原因。为提高ＣｕＺｎ钎料的综合性能,本文根据二次回归组合设计方法建立了合金元素与钎料润湿性能、剪切强度的回归方程,分析了合金元素对钎料的润湿性能及钎缝剪切强度的影响规律;将分层序列法与遗传算法相结合可以求解钎料润湿性能、钎缝剪切强度多目标优化问题。实验表明,采用本文提出的铜基钎料成分优化方法,可以获得优化的铜基钎料成分和性能。     

Ti-C-Al-Fe2O3体系原位合成钢基复合材料组织与形貌研究

采用Ti-C-Al-Fe2O3反应体系,结合铸造和自蔓延高温合成（SHS）两种工艺,在湿砂型中浇注高温熔融的钢水,引燃SHS压块,从而发生自蔓延高温合成反应,生成了高硬度的陶瓷相TiC、Al2O3.通过改变Ti-C-Al-Fe2O3体系组分配比,探讨了体系在金属液内SHS反应对原位内生TiC、Al2O3尺寸与分布的影响.结果表明,随着过量Al元素的增加,陶瓷增强颗粒尺寸逐渐减小且分布更均匀;稀土CeO2加入量的增加,增强区更加致密,稀土CeO2添加剂含量为0.8%时制备的复合材料中原位形成的Al2O3、TiC颗粒尺寸较小,分布均匀.     

中碳钢楔横轧轧制过程及组织性能研究

采用有限元方法对两种不同温度下三辊楔横轧中碳钢棒材的轧制过程进行了数值分析,分析了轧件横截面上温度及等效应变的分布规律,并通过实验研究分析测定了截面上不同位置处的显微组织及硬度分布。结果表明：轧件等效应变等值面在轧件横截面上呈环状分布,由心部向外变形程度逐渐增大;轧制过程中轧件内部存在明显的温升,大约在轧件1/2半径处温升最明显;轧件典型组织为珠光体与先共析铁素体,且从心部到表层组织逐渐变细。同时发现轧件外表层有产生脱碳,其组织为铁素体。     

Stainless steel binder for the development of novel TiC-reinforced steel cermets

Steel reinforced TiC composites are an attractive choice for wear resistance and corrosion resistance applications. TiC- reinforced 17-4PH maraging stainless matrix composites were processed by conventional powder metallurgy （P/M）. TiC-reinforced maraging stainless steel composites with 〉97% of theoretical density were fabricated. The microstructure, mechanical and wear properties of the composites were evaluated. The microstructure of these composites consisted of spherical and semi-spherical TiC particles. A few microcracks appeared in the composites, showing the presence of tensile stress in the composites produced during sintering. Typical properties, namely, hardness and bend strength were reported for the sintered composites. After heat treatment and aging, the increase of hardness was observed. The increase of hardness was attributed to the aging reaction in the 17-4PH stainless steel. The precipitates appeared in the microstructure and were responsible for the increase in hardness. The specific wear behavior of the composites was strongly dependent on the content of TiC particles, the interparticle spacing, and the presence of hard precipitates in the binder phase.     

Precipitation characteristic of high strength steels microalloyed with titanium produced by compact strip production

Transmission electron microscopy (TEM) and physics-chemical phase analysis were employed to investigate the precipitates in high strength steels microalloyed with Ti produced by compact strip production (CSP). It was seen that precipitates in Ti microalloyed steels mainly included TiN, Ti4C2S2, and TiC. The size of TiN particles varied from 50 to 500 nm, and they could precipitate during or before soaking. The Ti4C2S2 with the size of 40-100 nm might precipitate before rolling, and the TiC particles with the size of 5-50 nm precipitated heterogeneously. High Ti content would lead to the presence of bigger TiC particles that precipitated in austenite, and by contrast, TiC particles that precipitated in ferrite and the transformation of austenite to ferrite was smaller. They were less than 30 nm and mainly responsible for precipitate strengthening. It should be noted that the TiC particles in higher Ti content were generally smaller than those in the steel with a lower Ti content.     

硬质合金中温钎焊技术的实验研究

采用显微结构法,通过观察钎焊接头形成条件,研究了以B-Ag-1为钎料的硬质合金和钢的中温连接技术。实验表明,在感应电流为450～600 A时,B-Ag-1钎料能湿润并在硬质合金上铺展,形成组织均匀的钎缝,同时通过钎料中银原子和铜原子向硬质合金的扩散形成具有一定强度的界面。钎焊温度的降低以及铜缓冲层的加入,大大降低了钎焊过程的热应力,接头和母材上均未发现热裂纹。     

硬质合金中温钎焊技术的实验研究

采用显微结构法,通过观察钎焊接头形成条件,研究了以B-Ag-1为钎料的硬质合金和钢的中温连接技术。实验表明,在感应电流为450～600 A时,B-Ag-1钎料能湿润并在硬质合金上铺展,形成组织均匀的钎缝,同时通过钎料中银原子和铜原子向硬质合金的扩散形成具有一定强度的界面。钎焊温度的降低以及铜缓冲层的加入,大大降低了钎焊过程的热应力,接头和母材上均未发现热裂纹。     

奥氏体不锈钢窄间隙激光填丝焊接性能

为了取代窄间隙TIG填充热丝焊接厚板奥氏体不锈钢,采用窄间隙光纤激光填丝焊接方法焊接了板厚为15 mm的SUS306LN奥氏体不锈钢.通过试验研究,确定了最适于窄间隙激光填丝焊接的坡口形式和最佳焊接工艺参数.利用所得最佳焊接条件,获得了成形美观、无焊接缺陷、力学性能高及焊接变形小的焊接接头,焊缝金属与母材形成良好的冶金结合.该焊接方法为厚板结构件的窄间隙填丝焊接确立了一种高效率的焊接技术,并成功地把该项技术应用到核聚变超导线圈盒的焊接上.     

纳米银/环氧树脂纳米复合材料制备和性能表征

以乙二醇作为还原剂,采用微波法制备长径比不一的银纳米材料。采用SEM和XRD对不同长径比的纳米银进行了表征。以不同长径比的纳米银作为导热填料成功的制备了导热性能优异的环氧复合材料。环氧复合材料的热性能和力学性能测试表明：当长径比为33的银纳米线在较低的填充量具有较高的热导率,比填充纳米方块的环氧复合材料高约9倍（热导率为16.63 W·m-1.K-1）。填充银纳米线的环氧复合材料的抗剪切强度（以铝为基板的抗剪切强度为18.7 MPa）相比于填充相同体积分数的银纳米方块和银纳米棒的环氧复合材料均有不同程度的提高。     

600MPa级钛微合金化高强钢的组织与性能研究

采用光学显微镜、透射电镜以及能谱分析等对转炉CSP流程600 MPa级钛微合金化高强钢的组织及性能进行研究。结果表明,试验钢具有良好的综合力学性能,其典型组织为多边形铁素体加粒状贝氏体;位错和位错胞的强化作用成为钛微合金钢的主要强化机制之一;钢中M/A岛在增加试验钢强度的同时并未明显降低其韧性和塑性;试验钢中存在TiN、TiC和TiS等析出物,为钢的细晶强化和析出强化提供了保证;试验钢中存在大量纳米级铁碳析出物,其沉淀强化作用不容忽视。