A series of metal-rich metallaboranes of groups 7 and 9 comprising triply bridging borylene and boride units have been isolated and structurally characterized. Thermolysis of nido-[(RhCp*)2B3H7] (1...

Effect of Cooling Rate on Boride and Room Temperature Tensile Properties of β-Solidifying γ-TiAl Alloys

High-Resolution Transmission Electron Microscopic Study of Various Borides Precipitated in Superalloys

Characterization of borided Inconel 625 alloy with different boron chemicals

Boronizing of 50Fe-50Co alloy and its characterization

Preparation of USY Zeolite Supported Cobalt Boride Amorphous Alloy Catalysts and Its Application in Catalytic Hydrogen Production via Hydrolysis of Sodium Borohydride

Ni-based single-crystal superalloy DD5 has excellent high temperature properties, which is the preferred raw material for aero-engine turbine blade in recent year. In this research, DD5 superalloy was brazed by different contents of Ni-Co-Cr-W-B+DD99 mixed powder filler alloy. The microstructure evolution and interfacial formation mechanism of DD5 superalloy brazing joint were analyzed by SEM and EPMA. The mechanical properties of joint after solid solution treatment and aging treatment were tested. The results show that g-Ni primary phase formed firstly in the Ni-Co-Cr-W-B/DD99 interface during the brazing process, and then B element segregated and precipitated to fine granular M3B2 type boride. The residual liquid phase solidified and formed lastly to the M3B2 phase, g+g′ eutectic phase and g-Ni+Ni3B+CrB eutectic phase during cooling. With increasing the ratio of DD99 in mixed powder filler alloy, the low melting point eutectic phase and borides in the joint decrease and the uniformity of composition and microstructure of joint improve. When the ratio of DD99 increased to 70% (mass fraction) in the mixed powder filler alloy, it can be observed that element of B diffused to DD99 additive powder which result*国家自然科学基金项目51401210和51331005以及国家高技术研究发展计划项目2014AA041701资助 收到初稿日期: 2015-12-03,收到修改稿日期: 2016-04-17 作者简介:孙元,女, 1980年生,副研究员 DOI: 10.11900/0412.1961.2015.00622 第875-882页 pp.875-882

Подано результати дослідження з нанесення боросиліцидних покриттів порошковим методом на вуглецеві сталі. Досліджено структуру, фазовийсклад, розподіл елементів по товщині шару, тріщиностійкість і зносостійкість комплексних боросиліцидних покриттів в умовах сухого тертя – ковзання на повітрі. Встановлено, що боридні покриття, отримані в боруваль-ному середовищі з додаванням кремнію чи ферокремнію, складаються з боридних фаз FeB, Fe2B та додатково фази графіту. Боросиліцидні покриттямають в 1,2 – 1,4 рази вищу зносостійкість ніж боридні покриття. Показано, що боросиліціювання забезпечує оптимальний комплекс характеристикборидних фаз при зносі, а саме: достатню мікротвердість – 19 ГПа, підви-щення значення параметра К1с – 2,2 МПа·м0,5 порівняно з 1,2 МПа·м0,5 безкомплексного насичення і зростання значень напруг сколювання до 485 МПа впорівнянні з 170 МПа для боридних шарів. Рентгеноспектральним аналізомвиявлено розподіл кремнію по товщині боридних фаз зі зміною розчинностівід 0,01 до 0,5 % мас. при максимальному зосереджені кремнію в центральнійзоні фази Fe2B

Brittle to Ductile Transition Dependence upon the Transition Pressure of MB_2 (M=Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) Compounds

The microstructures,morphology of boride and grain refinement in directional solidified Ti-47Al-2Cr-2Nb-0.8B alloy with different withdrawal rates have been investigated.The results indicated that the primary phase,borides and their precipitation consequence varied with the increasing of withdrawal rates(0.36,5,10 and 20 mm/min).The morphologies of borides and grain refinement were affected by the solidification paths due to the different withdrawal rates.The alloy with fine grains and borides were obtained at the withdrawal rate of 5 mm/min.

Alkaline rechargeable batteries,such as Ni/Cd batteries and Ni/MH batteries have been widely used as power sources,however,their further applications are limited due to contamination of Cd in Ni/Cd batteries and lower discharge capacities of Ni/MH batteries.Some metal borides, such as Co-B,Ni-B,Fe-B,V-B and Ti-B,have been known to own very high discharge capacity in alkaline aqueous solution,in which Co-B alloy exhibits the highest reversible discharge capacity and the best cyclic stability.However,the reversible capacity of Co-B alloy prepared by arc melting process is usually less than 250 mA·h/g,which is only one fourth of the theoretical capacity of the alloy electrode(908 mA·h/g).In the present study,chemical reduction method was used to prepare Co-B alloy to further enhance the electrochemical capacity of the alloy.A series of ultrafine powders of amorphous Co-B alloys,Co_(0.68)B_(0.32),Co_(0.55)B_(0.45) and Co_(0.50)B_(0.50),were prepared by reducing CoSO_4 with solution of NaBH_4.Electrochemical measurements indicate that the prepared alloys exhibit excellent electrochemical properties.At a high current density of 300 mA/g,the initial discharge capacities of these alloys are 510.6,666.4 and 667.2 mA·h/g,respectively,their discharge capacities still keep 331.6,379.5 and 390.5 mA·h/g after 60 cyc,respectively.Even at a discharge current density as high as 1200 mA/g,the three alloys still deliver reversible capacities of 336.2,373.4 and 390.1 mA·h/g,respectively.In the Co-B alloy electrodes,the boron atoms have two functions.First, boron can be oxidized to BO_3~(3-),thereby partly contributes to the discharge capacity.Second,most importantly,the gradual dissolution of boron into the electrolyte(in the form of BO_3~(3-)) during the charging/discharging creates a new surface in the electrodes,which can effectively increase the surface area of the active material in contact with the electrolyte.The alloy with higher boron content thereby can produce a larger reaction surface area by boron dissolution than the alloy prepared with lower B content.So the higher B content in the Co-B alloys can be helpful for improving their electrochemical properties.

Microstructure of the wear-resisting functional gradient borides materials on the agricultural machinery casting surface.

Mnを添加したMo<SUB>2</SUB>NiB<SUB>2</SUB>型複硼化物系サーメットの組織と機械的特性

Effects of alloying elements on the mechanical properties and boride crystal structure of Mo2NiB2 base hard alloys were studied using the alloys whose compositions were Ni-6 mass%B-58.6 mass%Mo-(0-20)mass%Cr and Ni-6 mass%B-58.6 mass%Mo-10 mass%X (X: V, Fe, Co, Ti, Mn, Zr, Nb and W). The alloys consist of a Mo2NiB2 type ternary boride as a hard phase and a nickel base binder alloyed with Mo and other elements, both of which are formed by reaction boronizing sintering.The transverse-rupture strength (TRS) of the Cr containing alloys depended strongly on the microstructure, which varied significantly with Cr content. The maximum TRS of 2.3 GPa and a hardness of HRA87 were obtained at 10 mass%Cr content. A crystal structural change from the orthorhombic M3B2 (M: Metal) to the tetragonal M3B2 was observed with increasing Cr content. The highest TRS value at 10 mass%Cr was attributed to the formation of fine M3B2 particles with a tetragonal structure.In the eight additional elements, vanadium showed the same effects as chromium on the mechanical properties associated with the crystal structural change of M3B2 from the orthorhombic to the tetragonal. Additions of the other alloying elements did not lead to the crystal structural change of M3B2 and the improvement of the mechanical properties of the Mo2NiB2 base hard alloys.The Rietveld analysis method successfully revealed the atomic configurations as well as the lattice parameters of the unit cells of the orthorhombic M3B2 at non-Cr and the tetragonal M3B2 at 10 mass%Cr.

(Mo, Ni)硼化物系硬質合金の諸特性に及ぼすCr添加量の影響

Sm2B5 boride and its structure

Fivefold symmetry in boron and borides

Examen par spectroscopie Mossbauer pour approfondir les resultats de diffraction X sur du fer Armco borure pendant 15 h a 850 C par un melange de B 4 C contenant 20% de poudre de SiC et active par KBF 4 (2,5%). Mise en evidence d'une phase FeB x et d'une phase (B,Fe) ss amorphe ou tres finement dispersee. Resultats analogues sur des alliages synthetiques faiblement allies (jusqu'a 1,35% en poids) avec Mn ou Cr

Improving the technique of boriding from pastes

Chromium coatings with oxides, caebides, and borides