Carbide-binder interface ledges in (V,Ti) C+ (Ni,Mo) cermets

Interface ledges have been observed by transmission electron microscopy between the carbide and binder phases in (V, Ti) C+ (Ni, Mo) cemented carbides. It is proposed that these ledges can act as dislocation sources in a manner analogous to that of polycrys-talline metals and alloys. Such a concept can provide a physical basis for the empirically observed relation between hardness and the binder mean free path in cemented carbides. R. K. VISWANADHAM, formerly with Martin Marietta Laboratories, 1450 S. Rolling Road, Baltimore, MD 21227     

由粉末冶金Fe(Cr,Mo)钢制备的同步器齿毂的力学性能

试验测定零件本身的强度性能是困难的,因此通常不采用此类数据.本文介绍了一种用于直接测定零件本身强度性能的方法,即用水射流切割零件,随后进行磨加工制备小型矩形试棒(约40mm×5mm×5mm)测定数据.采用典型粉末冶金零件——粉末冶金高合金化Fe(Cr,Mo)钢同步器齿毂制备的小型试棒测定抗拉强度、冲击强度及3点弯曲横向断裂强度,并和常规拉伸试样(DIN EN ISO 2740)的强度与冲击性能进行了对比.结果表明,由同步器齿毂与常规试样测定的数据都在试验误差范围之内,完全一致.为了证实对比的有效性,还用全面的化学与显微组织分析证明了2种试样的相似性.最后,建立了小型拉伸试棒的横向断裂强度与抗拉强度之间的相关性.     

First-principles computations of mechanical properties of Ni2Cr and Ni2Mo

Nickel-based alloys are being considered for use as the outer container of the waste package for the disposal of high-level nuclear waste. During fabrication processes and long-term storage, Ni-based alloy outer containers can undergo microstructural changes due to the formation of Ni₂Cr, Ni₂Mo, and Ni₂(Cr, Mo), which are ordered orthorhombic (oI6) phases whose mechanical properties are unknown because of fabrication difficulties. To circumvent the experimental limitation, a first-principles quantum-mechanical code based on the full-potential linearized augmented plane-wave (FLAPW) method was used to compute the elastic constants and the theoretical stress-strain curves of Ni₂Cr and Ni₂Mo. The theoretical mechanical properties were then correlated with charge-density distributions of the stressed oI6 unit cell to identify the critical conditions at the onset of fracture. Using first-principles results as material input, the unstable stacking energy and the Peierls-Nabarro (P-N) barrier energy were computed and used to estimate the tensile ductility and fracture toughness of Ni₂Cr and Ni₂Mo. The influences of the elastic anisotropy and slip vector on dislocation mobility in Ni₂Cr and Ni₂Mo are identified and contrasted to those in MoSi₂ with a tetragonal (tI6) crystal structure. This article is based on a presentation made in the symposium “Computational Aspects of Mechanical Properties of Materials,” which occurred at the 2005 TMS Annual Meeting, February 13–17, 2005, in San Francisco, CA, under the auspices of the MPMD-Computational Materials Science & Engineering (Jt. ASM-MSCTS) Committee.     

Thermionic emission properties of cermets of eutectic compositions in Me(IV)-(C,B)-(Mo,Re, W) systems

Conclusions Sintered eutectic (Ti, Zr, Hf)C-(Mo, Re, W) and ZrB₂-(Mo, Re, W) cathode cermets having a quasieutectic coarse-conglomerate structure are characterized by high stability of emission, and their effective work function is lower than that of their most emission-active components. The rapid stabilization of the emission characteristics of the eutectic cathode cermet composites is linked with the specific character of electron exchange between their phases, which creates optimum conditions for the formation of a self-stabilized structure on the surface of an emitter. The relative fall in work function exhibited by the cathode cermets investigated compared with their metallike compound components grows with increasing work function of their pure metallic components. Composite emitters of the eutectic compositions of the MeC (MeB₂)-Me' (where Me' = Mo, Re, W) systems are film-type emitters, on whose surfaces thin layers of the metal Me' form during heat treatment (sintering) and actual operation. The metal surface layers adsorb atoms from the metallike compounds MeC and MeB₂, which are supplied to the surfaces of the emitters by diffusion.Translated from Poroshkovaya Metallurgiya, No. 1(205), pp. 81–87, January, 1980.     

氮对0Cr13Ni4Mo马氏体不锈钢机械性能的影响

研究结果表明，含0．018％N的低氮对0Cr13Ni4Mo马氏体不锈钢未出现中温回火脆性，含0．054％N的高氮钢有中温回火脆性出现，经600℃高温回火后可获得高的强韧性配合和极高的－60℃低温冲击韧性。     

Contact interaction,structure, and properties of W(Mo,Cr)-Cu composites with additives

The results of research on the effect of additives on the adhesive characteristics and phase-boundary formation in W(Mo, Cr)-Cu systems are summarized. The distinctive features of structure formation and the properties of powder composites compacted in the presence of a liquid phase have been studied. Composites with optimal properties (high-temperature hardness, electrical conductivity, high adhesiveness, and stable structure) have been identified.Institute of Problems in Material Science, National Academy of Sciences of Ukraine, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8, pp. 46–57, July–August, 1996.     

Influence of Tempering Process on Mechanical Properties of 00Cr13Ni4Mo Supermartensitic Stainless Steel

To investigate the influence of tempering process on microstructural evolutions and mechanical properties of 00Cr13Ni4Mo supermartensitic stainless steel(SMSS),specimens were tempered in the temperature range of 520-720 ℃ for 3 h followed by air cooling and an optimized tempering temperature was chosen to prolong holding time from 3 to 12 h.After heat treatments,microstructure examination was conducted by scanning electron microscope,X-ray diffraction examinations,hardness measurements and tensile tests.The results revealed that the superior mechanical properties were achieved by quenching at 1040 ℃ for 1 h+water cooling and tempering at 600 ℃ for 3 h+air cooling.Increasing isothermal tempering time could improve the toughness notably.It was believed that the property was correlated with the microstructure of tempered lath martensite and retained austenite.More retained austenite content is beneficial to the higher toughness of the SMSS.     

碳纳米管对低Ni含量Ti(C,N)基金属陶瓷组织与性能的影响

为了探讨碳纳米管对Ti(C,N)基金属陶瓷性能的影响,添加不同质量分数的碳纳米管作为增强相,采用粉末冶金法制备Ti(C,N)基金属陶瓷材料.通过对材料的显微组织分析,抗弯、硬度等力学性能的测试,研究了碳纳米管含量对Ti(C,N)基金属陶瓷的组织和性能的影响.结果表明:添加碳纳米管后,低Ni含量的金属陶瓷材料的组织结构为典型的芯-壳结构,由黑色芯部、具有明显包覆层的组织,白色芯部、包覆层不明显的组织,粘结相组成;相同烧结温度下,添加≤1％(质量分数)的CNTs时,随碳纳米管含量增多,材料抗弯强度下降;添加Ni包覆的碳纳米管的金属陶瓷材料的性能比添加未做过表面处理的碳纳米管的材料性能好.     

固溶处理对00Cr27Ni7Mo5N不锈钢的组织及力学性能的影响

 研究了不同固溶处理温度对特超级双相不锈钢00Cr27Ni7Mo5N组织及力学性能的影响。采用光镜、扫描电镜、能谱仪、显微硬度、冲击和拉伸测试等手段研究σ相的析出规律及其对力学性能的影响。运用Thermo-Calc热力学软件计算00Cr27Ni7Mo5N相含量随温度的变化,并与测试结果进行对比分析。研究结果表明,当固溶温度在800～1050℃之间,00Cr27Ni7Mo5N有大量金属间化合物σ相析出,导致钢的强度和硬度增加,塑韧性显著下降。当固溶温度在1070～1200℃时,钢中σ相溶解,钢的塑韧性提高,硬度下降。1100℃固溶处理时,00Cr27Ni7Mo5N具有最佳的综合力学性能。     

钛含量对00Cr13Ni8Mo2TiNbAl马氏体时效不锈钢机械性能的影响

运用拉伸试验，金相组织分析等方法研究了合金元素钛含量对00Cr13Ni8Mo2TiNbAl马氏体时效不锈钢机械性能的影响。研究发现，钛含量增加，使钢中获得细小沉淀物的弥散分布，细化晶粒，增强时效硬化，从而提高该钢的抗拉强度。     

固溶温度对00Cr22Ni5Mo3N钢组织及力学性能的影响

研究了固溶温度对00Cr22Ni5Mo3N钢组织及力学性能的影响。结果表明：在1000-1150℃之间,随着固溶温度的提高,00Cr22Ni5Mo3N钢组织中的铁素体含量呈直线上升;钢的强度和硬度先下降后上升,在1050℃达到最低点;钢的塑、韧性变化明显,当固溶温度低于950℃时,钢的塑、韧性急剧下降。经过分析,塑、韧性的下降主要是脆性相的析出所致。     

亚微米级Ti(C,N)基金属陶瓷的显微组织和力学性能

以亚微米级的粉末为原料制备Ti（C,N）基金属陶瓷,通过透射电镜（TEM）、扫描电镜（SEM）、能谱分析（EDX）等方法研究其在烧结过程中的组织结构变化规律及特点,并探讨烧结工艺参数对金属陶瓷力学性能的影响。结果表明,随着烧结温度升高,Ti（C,N）基金属陶瓷的组织更均匀,硬质颗粒逐渐球化,表面的Rim相更完整。Rim相分为两层,里层Rim相的Mo、W含量比外层Rim相高,里层Rim相是在固相烧结阶段形成的,外层Rim相是在液相烧结阶段形成的。Rim相的形成及晶粒长大都是通过溶解-析出机制进行的。在1 410℃下保温60 min,可获得较佳的力学性能,抗弯强度达2 266 MPa,硬度为HRA 90.6。     

Preparation and properties of VC + Ni cermets with controlled carbon-to-metal ratio

A series of VC + Ni cermets was prepared where the carbon to metal (C / M) ratio of the carbide was varied from 0.86 to 0.75. Transmission electron microscopy and diffraction were used to determine the C/M ratio of the carbide and binder microstructure. At high C/M ratios, the carbide was principally V₈C₇ or V₈C₇ + V₆C₅, while at low C/M ratios the carbide was V₆C₅ or V₆C₅ + V₄C₃. The vanadium content of the binder increases as the C/M ratio of the carbide is decreased. The mechanical behavior of the cermets was evaluated by crack resistance and hardness measurements. In inverse crack resistancevs hardness plots, the VC + Ni cermets exhibit three types of behavior (labeled Type I, II, and III) in order of decreasing fracture toughness for a given hardness. Auger electron spectroscopy and scanning electron microscopy show that the three behavior types are characterized by differences in the dominant fracture mode. The fracture mode is principally transgranular fracture through the binder for Type I, transgranular cleavage of carbides for Type III, and intergranular or mixed fracture mode for Type II. The differences in fracture mode and mechanical behavior are induced by changes in microstructural features, as well as changes in the binder composition and formation of second phases. These results suggest that binder strengthening is a viable means to improving cermet performance only in systems when the cleavage energy of the carbide is sufficiently high to withstand the stresses generated by plastic flow in the binder. Formerly with Martin Marietta Laboratories, Baltimore     

316L（00Cr17Ni14Mo2）特级优质的钢管试制

试制的316L（00Cr17Ni14Mo2）特级优质钢管技术要求苛刻，不仅要有较好室温性能，也要有较好的高温性能，对管壁、表面质量要求极为严格。试制结果表明，化学成份、室温性能、高温性能、晶腐、涡流探伤、超声波探伤、水压试验、氦气检漏等质量指标满足用户技术要求，工艺路线成熟。     

固溶温度对马氏体时效钢00Ni14Cr3Mo3Ti组织和力学性能的影响

研究了马氏体时效钢00Ni14Cr3Mo3Ti(%:0.002C、14.06Ni、3.19Cr、3.06Mo、1.32Ti)750～1 050℃固溶处理的组织和力学性能。结果表明,≤900℃固溶处理,该钢奥氏体晶粒和强度无明显变化,固溶温度超过900℃时钢的奥氏体晶粒显著增大,钢的强度呈下降趋势。当固溶温度由750℃增加至900℃时,随固溶处理温度提高,钢中Fe2Mo相量降低,810℃时完全溶解,钢的冲击功由32 J提高至61 J,当固溶温度由900℃增至1 050℃,随奥氏体晶粒增大,钢的冲击功由61 J 降至26 J。