Tribological Properties of Composite Materials Based on Refractory Titanium Compounds

The tribological properties have been examined for composite materials based on binary titanium-chromium boride and titanium nitride under conditions of dry friction over a wide speed range (1–25 m/sec). The materials have good tribological properties, which exceed by almost an order of magnitude those of known materials. Specifications are formulated for materials promising for high-speed friction units. A necessary condition for viability in high-speed friction units is high strength of the adhesion between the films of oxidation products, and another is low tendency for adhesion with the counterbody. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(444), pp. 58–64, July–August, 2005.     

Tribological Properties of Hard Alloys Based on Chromium Carbide

Hard alloys of the type KKhN and KKhNF were studied and shown to have low coefficient of friction (f = 0.21-0.17) and wear rate (I = 5.7-7.0 m/km) at sliding velocity 15 m/sec and load 7 MPa, which make them promising for use as antifrictional materials in dry friction units under load. Oxide films formed at the surface of the hard alloys play the role of solid lubricants and decrease frictional losses.     

Structure Formation,Electrophysical and Mechanical Properties of an Electrically Conducting Ceramic Composite Based on Silicon and Boron Carbides

How the structure of electrically conducting ceramic composites in the SiC B₄C system is formed has been studied. The mechanical and electrophysical properties have been investigated as a function of the ratio of the components and the sintering conditions.     

Effect of Rare Earths on Microstructure and Properties of TiC-based Cermet／Cu Alloy Composite Wear Resistant Materials

The effect of rare earth (RE) oxide on the microstructure and properties of TiC-based cermet/Cu alloy composite hardfacing materials was investigated by using scanning electron microscope (SEM), transmission electron microscope(TEM), impact test and wear test. The mechanism of RE oxide for improving the phase structure and the impact toughness was also discussed. The experimental results indicate that the microstructure of the matrix can be refined, and the micro- porous defects can be eliminated by adding RE oxide into the composite materials. The polycrystalline and amorphous phase structure is formed at the interface of cermet and matrix metal. The formed structure enhances the conjoint strength of interface. The frictional wear resistance can be improved obviously, although the microhardncss of the matrix metal can not be effectively increased by adding RE oxide.     

Influence of Shock Wave Treatment of Boron Carbide Powders on the Structure and Properties of Hot-Pressed Polycrystals Based on Such Powders

The influence of deformation pre-treatment (milling in a planetary mill and shock-wave treatment) of B₄C powders of different size composition on their structure as well as the structure and mechanical properties of samples that have been hot-pressed from these powders is investigated. It is shown that treatment by shock waves produces a substantial change in the structure of the powders, and this tends to increase the mechanical properties of the polycrystalline cakes. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(444), pp. 118–127, July–August, 2005.     

无压浸渗法制备SiCp/Al复合材料的微观组织与力学性能

采用无压浸渗方法制备了SiC颗粒增强铝基复合材料，研究了材料的微观组织和力学性能。结果表明，复合材料浸渗完全，SiC颗粒分布均匀，无偏聚现象。铸造态复合材料中存在界面反应，经过透射电镜观察和XRD分析确认该界面反应物为MgAl2O4。界面反应的存在提高了润湿性，促进了无压自发浸渗。高温热暴露处理可以提高复合材料的布氏硬度，热暴露处理后的界面反应物呈块状弥散分布，但是反应物的数量略有增加。     

微量添加晶界合金对烧结Nd-Fe-B力学性能及微观结构的影响

采用双合金法制备系列烧结Nd—Fe—B磁体(保持其主合金成分不变：Ndl4．1Dy0．5Fe79.0B6.4(原子分数)，所添加的晶界合金中的B含量从0．95％(原子分数)逐步增加到6．95％(原子分数))，研究了微量添加晶界合金对烧结Nd—Fe—B力学性能及微观结构的影响。研究结果表明：微量添加晶界合金所制备的磁体，其抗弯强度值普遍高于单合金法制得的磁体；前者的抗弯强度最高可达397MPa，高于铸造，热压磁体的抗弯值，而后者的抗弯强度仅为309MPa。由相结构分析可知，当添加的晶界合金中的B含量为O．95(原子分数)，主相晶格的四方度减小，这时磁体具有最高的抗弯强度。另外，微量添加晶界合金，可使磁体中晶界相的分布更加均匀，从而基本上消除了主相晶粒直接接触的现象，使晶粒的不规则长大得到抑制。这也是微量添加晶界合金后磁体具有较高抗弯强度的原因之一。对磁性能的研究结果表明，微量添加晶界合金几乎不影响烧结Nd—Fe—B磁体的磁性能。     

Effect of Heat Treatment on the Mechanical Properties and the Carbide Characteristics of a High Strength Low Alloy Steel

Effect of heat treatment on the mechanical properties and the corresponding morphology changes of carbides such as (NbTi)C and Mo,Cr rich carbides in a high strength steel was studied in the paper.It was found that the strength depend more on tempering temperature than quenching temperature.While the toughness seemed to be sensitive to both quenching temperature and tempering temperature.Under the as water quenched condition,the toughness gave a peak value at the quenching temperature of 860℃.Under the as tempered condition,the toughness showed a temper brittleness at the temperature range of 230℃ to 450℃.The morphology changes of the carbides in the experimental steel were explained from the view of the thermal dynamic behavior.     

Effect of Cooling Rate after hot Deformation on Structure and Mechanical Properties of Low Alloy Wear Resistance Cast iron

The effect of cooling rate after 40% hot deformation on structure and mechanical properties of low alloy wear resistance cast iron was investigated by metallographic, scanning electron microscopes and detection of properties. The results show that for the cast steel after deformed, the amount of granular carbides of precipitation during the cooling decreased with the increase of the cooling rate, but the hardness was obviously enhanced, as a result, better mechanical properties will be obtained by force air cooling (cooling rate is about 7℃·s-1). And the reason of the change for structure and mechanical properties of the cast steel were analyzed.     

制备工艺对Cu-Ag合金原位复合材料结构与性能的影响

研究了包括凝固速率、冷变形和中间热处理对Cu-10Ag合金原位复合材料结构与性能的影响。观察了铸态组织及其在冷变形和中间热处理后的变化,测量了材料的极限拉伸强度(UTS)与导电率。观察到了两阶段应变强化效应,讨论了影响强度与导电率的因素。冷却速率在10~103K.s-1范围内的凝固条件和中间热处理明显影响Cu-10Ag合金原位复合材料的结构与性能。     

Co和Cr3C2对硬质合金组织和性能的影响

采用粉末冶金工艺制备了三种不同Co和Cr3C2含量的硬质合金材料。在常温下分别测量了材料的晶粒度、硬度和抗弯强度,并通过SEM照片等对材料的金相显微组织、断口形貌进行分析。结果表明:硬质合金中粘结相Co含量增多,其硬度下降,抗弯强度升高;微量碳化物Cr3C2在硬质合金中起到细化晶粒的作用,在高钴硬质合金中添加微量碳化物Cr3C2,能使材料具有高硬度、高抗弯强度的良好综合性能。     

Effect of Surface Treatment with Concentrated Energy Fluxes on the Properties of Composite Materials Based on Silicon Carbide and Coatings Made from Such Composites

Based on a study of the structure and composition of the composite ceramic SiC - Al₂O₃ - ZrO₂, its tribomechanical properties and behavior in high-temperature corrosion, we recommend the material for use as sealing elements and for deposition of wear-resistant and corrosion-resistant coatings. We have studied the formation of gradient layers when the ceramic surface is modified with refractory titanium compounds TiN - TiB₂ (1:1) with an Fe(Ni) - Cr - Al undercoat using concentrated solar radiation and when the steel surface is modified with laser irradiation of the SiC - Al₂O₃ - ZrO₂ coats. We have shown that laser modification of steel by the silicon carbide-based composite increases its corrosion resistance by a factor of 4–5 at 800–900 °C. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(444), pp. 91–99, July–August, 2005.     

Effect of Cooling Rate on Structure and Properties of Wear-Resistant Low Chromium Cast Iron after Hot Deformation

Thereismuchinterestinwear resistantlow chromiumcastironforitshighhardnessandgood abrasionresistance.However,itstoughnessisvery lowduetothecontinuousnet shapeddistributionof carbide.Hotplasticdeformationcanbreakdownthe netcarbideandimprovecomprehensivemech…     

用反应压力熔渗法制备高含量SiCp/6013Al复合材料及其力学性能

研究了反应压力熔渗法制备高含量SiCp／Al复合材料的工艺过程及其抗弯强度。研究表明：通过适当的粒度配比,可在低温、低压力下熔渗制备组织均匀的高含量SiCp／6013Al复合材料,SiC颗粒含量达到63％;复合材料的强度在很大程度上依赖于SiC颗粒尺寸及界面反应程度,合适的界面结合及细SiC颗粒的掺入有利于复合材料强度的提高,最高可达445MPa。     

Co/Ni比对93W-Co-Ni钨合金烧结温度及力学性能的影响

以Co、Ni作黏结剂,选择不同Co/Ni比,用粉末冶金法制备出HRC硬度在30⁴3之间的93W-Co-Ni钨合金。采用光学金相、扫描电镜对合金组织形貌进行表征,采用准静态拉伸试验对合金的抗拉强度及延伸率进行测试,采用洛氏硬度计对合金硬度进行测定。结果表明:随着Co/Ni比增加,合金的烧结温度逐渐增加,其抗拉强度与延伸率急剧降低,而硬度先增加之后趋于稳定;当Co/Ni≥1.0时,合金抗拉强度很低,延伸率≤1%;当Co/Ni≥4时,其HRC硬度值稳定在4143之间的93W-Co-Ni钨合金。采用光学金相、扫描电镜对合金组织形貌进行表征,采用准静态拉伸试验对合金的抗拉强度及延伸率进行测试,采用洛氏硬度计对合金硬度进行测定。结果表明:随着Co/Ni比增加,合金的烧结温度逐渐增加,其抗拉强度与延伸率急剧降低,而硬度先增加之后趋于稳定;当Co/Ni≥1.0时,合金抗拉强度很低,延伸率≤1%;当Co/Ni≥4时,其HRC硬度值稳定在41⁴3之间,明显高于一般的W-Ni-Fe合金,这主要与Co对W基体的润湿性较差及两者之间易形成脆性化合物Co7W6有关。     

等离子喷涂高温润滑涂层的组织与力学性能研究

选取了具有优异的高温性能和一定的自润滑性能的高温镍基合金作为复合涂层基体材料,润滑相则分别从高、中、低温固体润滑剂中选取了Ag、CaF2、石墨（C）、MoS、BN为基本润滑组元;耐磨相则选用了在高温下具有良好的抗氧化性能及耐磨损性能的碳化铬（Cr3C2）硬质粒子,采用等离子喷涂技术制备了具有极佳相容性的高温润滑涂层。涂层的结合强度测定、硬度测定和扫描电镜分析均显示出涂层的梯度结构优于单层结构。梯度结构缓和了涂层内部的物理性能差异,不仪使涂层的硬度得到平缓过渡,而且使涂层的结合强度大大提高。有效改善了涂层的性能。     

Effect of Rare Earth Composite Modification on Microstructure and Properties of a New Cast Hot-Work Die Steel

The effects of RE modification on structure and the properties of a new cast hot-work die (CHD) steel were investigated. The grains of the CHD steel are refined by RE modification. With the increase of RE addition, both grain size and inclusion amount are reduced. Appropriate amount of RE results in decrease in inclusion amount and formation of spheroidal inclusions uniformly - distributed in steel, so that the morphology and distribution of inclusions are improved. RE composite modification favors the formation of bainite, austenite and fine lath martensite with dense dislocation. When the residual RE content reaches 0.02 %, no obvious changes in strength and hardness are found, while fracture toughness and threshold of fatigue crack growth are increased. The impact toughness, elongation and reduction of cross sectional area are increased by a factor of two, and thermal fatigue resistance is also improved.     

旋转速度对（WC+B4C）p/6063Al复合材料搅拌摩擦焊接头力学性能和微观组织的影响

搅拌摩擦焊的旋转速度对接头焊缝形貌、微观组织和力学性能均有较大的影响。采用搅拌摩擦焊方法对5 mm厚的(WC+B4C)p/6063Al复合材料进行焊接试验,固定焊接速度为100 mm.min-1,旋转速度分别为900,1100,1300和1500 r.min-1,焊后观察焊缝宏观形貌和各种缺陷,并对接头的微观组织和力学性能进行了分析。焊缝宏观缺陷研究结果表明,随着旋转速度的升高,焊接热输入量增大,金属流动性得到改善,飞边、沟槽等宏观缺陷显著增多,焊缝形貌越来越粗糙;接头微观组织研究表明,由于搅拌头的搅拌作用,相比于母材,在焊核区增强相颗粒分布更加均匀,更多增强相颗粒发生破碎,且随着旋转速度的增加,这种趋势增强。对接头的抗拉强度研究表明,在1300 r.min-1以内时,随着旋转速度增加,接头抗拉强度随之增加,最大值为166 MPa,进一步增加到1500 r.min-1时,强度又有所降低,为154 MPa。