W, Co, Ni对时效合金强度和韧性的影响

研究了Ｗ,Ｃｏ,Ｎｉ对时效合金强度和韧性的影响。结果表明：高Ｃｏ的ＦｅＷＣｏ合金有强的时效硬化能力,但其韧性较低。以Ｎｉ取代部分Ｃｏ之后,合金的韧性得到大的提高。ＦｅＷＣｏ合金的Ｃｏ量约２３％,Ｗ,Ｍｏ总量超过１８％时,硬度增加甚少,韧性损害较大,而ＦｅＷＣｏＮｉ的Ｃｏ当量达２３％,Ｗ,Ｍｏ总量达２４％时获得最佳的强度和韧性的配合。萃取化合物的Ｘ射线衍射（ＸＲＤ）分析表明,时效合金的主要金属间化合物是Ｆｅ３Ｗ２型,还有Ｆｅ７Ｗ６和Ｆｅ２Ｗ型化合物。淬火态、退火态萃取物的化学分析表明,时效合金中,Ｗ,Ｍｏ主要存在于化合物中,而Ｃｏ,Ｎｉ主要存在于固溶体中。时效硬化主要通过Ｗ,Ｍｏ金属间化合物的析出引起。而Ｃｏ,Ｎｉ主要通过影响析出相的数量、析出物形态及分布状态来影响时效硬化。     

WC（15—20）m?—Co—Ni硬质合金研究

研究了富铁的高粘结剂ＷＣ基硬质合金,其基本化学成分为ＷＣ－（１５－２０ｍ％）（Ｆｅ－１９％Ｃｏ－１６％Ｎｉ）,根据ＷＣ粉原始颗粒度等的不同,试制了４种硬质合金,其物理机械性能均达到或相当地相应牌号ＷＣ－Ｃｏ基硬质合金的水平,对２０％粘结相的２种硬质合金做了应用试验,均取得了满意的使用效果。     

钛制机动艇船台

研究了配碳量与Ｎｉ／Ｃｏ比对ＷＣ－９（Ｎｉ－Ｃｏ）硬质合金抗率强度的影响。实验结果表明：ＷＣ－３Ｎｉ－６Ｃｏ的配碳量是６．０４ｗｔ％时，其抗弯强度与ＷＣ－９Ｃｏ硬质合金相当；Ｎｉ的分布均匀性对抗弯强度的影响极其重要，粗粒Ｎｉ粉或（和）较多η相的存在都会使硬质合金形成脆性断裂，直接影响合金的抗弯强度。     

镍代钴WC－9（Ni－Co）硬质合金的研究

研究了配碳量与Ｎｉ／Ｃｏ比对ＷＣ－９（Ｎｉ－Ｃｏ）硬质合金抗弯强度的影响。实验结果表明：ＷＣ－３Ｎｉ－６Ｃｏ的配碳量是６．０４ｗｔ％时，其抗弯强度与ＷＣ－９Ｃｏ硬质合金相当；Ｎｉ的分布均匀性对抗弯强度的影响极其重要，粗粒Ｎｉ粉或（和）较多η相的存在都会使硬质合金形成脆性断裂，直接影响合金的抗弯强度。     

HREM STUDY OF GRAIN BOUNDARY PHASES IN Fe-Ni-Co-Nb-Ti SUPERALLOY

ＨＲＥＭＳＴＵＤＹＯＦＧＲＡＩＮＢＯＵＮＤＡＲＹＰＨＡＳＥＳＩＮＦｅ－Ｎｉ－Ｃｏ－Ｎｂ－ＴｉＳＵＰＥＲＡＬＬＯＹＲ．Ｍ．Ｗａｎｇ；Ｃ．Ｚ．Ｌｉ；Ｓ．Ｗ．ＺｈａｎｇａｎｄＭ．Ｇ．Ｙａｎ（１）ＩｎｓｔｉｔｕｔｅｏｆＡｅｒｏｎａｕｔｉｃａｌＭａｔｅｒｉａｌ...     

CRYSTALLOGRAPHIC PROPERTIES OF AN INHERENT LOW－ENERGY INTERFACE（1■1）Cu／／（0001）_（AIN）IN Cu－AlN BICRYS

ＣＲＹＳＴＡＬＬＯＧＲＡＰＨＩＣＰＲＯＰＥＲＴＩＥＳＯＦＡＮＩＮＨＥＲＥＮＴＬＯＷ－ＥＮＥＲＧＹＩＮＴＥＲＦＡＣＥ（１■１）Ｃｕ／／（０００１）_（ＡＩＮ）ＩＮＣｕ－ＡｌＮＢＩＣＲＹＳＴＡＬ￥Ｊ．Ｄｕ,Ｇ．Ｙ．ＹａｎｇａｎｄＳ．Ｈａｇｅｇｅｇｅ（Ｇｅ?..     

掺杂Fe对贮氢合金Ml（Ni—Co—Mn—Ti）5电化学性能的影响

针对混合稀土金属中含有不定量的Ｆｅ杂质及贮氢电极合金在熔炼过程中容易混入Ｆｅ杂质的特点,采用在Ｍｌ（Ｎｉ－Ｃｏ－Ｍｎ－Ｔｉ）５合金中入为地添加不同量Ｆｅ的方法,系统地研究了Ｆｅ掺 对贮氢电极合金Ｍｌ（Ｎｉ－Ｃｏ－Ｍｎ－Ｔｉ）５电化学性能的影响。     

Y2O3对WC—8Ni硬质合金物理机械性能和显微结构的影响

本文研究了添加微量Ｙ２Ｏ３对ＷＣ－８Ｎｉ硬质合金物理机械性能和显微结构的影响。研究发现Ｙ２Ｏ３对合金的密度、硬度影响不大，但抗弯强度、耐磨性提高幅度较大，分别为５０．４％和８２．７％，达到并超过ＹＧ８合金性能。利用显微分析方法观察到Ｙ相微粒弥散分布在Ｎｉ相和ＷＣ与Ｎｉ的相界处；过量Ｙ２Ｏ３会生成Ｙ的聚集相；ＷＣ晶粒均匀、细化；孔隙度降低；α－Ｗ２Ｃ相消失。讨论了Ｙ２Ｏ３对显微结构影响的机理。     

贮氢电极合金Ml（NiMnTi）4.2Co0.8—XFex（x=0—0.8）的电化学性能

详细地研究了Ｍｌ（ＮｉＭｎＴｉ）４．２Ｃｏ０．８－ｘＦｅｘ（ｘ＝０－０．８）合金的电化学性能。试验发现,随着Ｆｅ含量ｘ从０增加至０．,合金的活化性能得到改善,但最大放电容量从３０２ｍＡｈ／ｇ逐渐降低到２８０ｍＡｈ／ｇ,高倍率放电性能从７８．５％缓慢降至７２．５％;当Ｆｅ含量ｘ≤０．４时,合金的自放电率与高Ｃｏ合金（ｘ＝０）相比有所降低,但当Ｆｅ含量ｘ超过０．４后,合金的自放电率较高Ｃｏ合金有所上升     

Co含量对（WC—Co／NiCrBSi）复合钎焊涂层耐磨性的影响

采用真空钎焊技术,将ＷＣ－Ｃｏ硬质合金粉和ｉＣｒＢＳｉ（ＡＷＳ ＢＮｉ－２）合金粉钎焊到４５＃钢表面,得到（ＷＣ－Ｃｏ／ｎｉＣｒＢＳｉ）复合钎焊涂层。在不同钎焊工艺下,涂层自身 和层／基体间的拉伸结合强度分别达（１００－１４０）ＭＰａ和（３００－３６０）ＭＰａ。研究了Ｃｏ含量对（ＷＣ－Ｃｏ／ＮｉＣｒＢＳｉ）复合涂层磨损性能的影响。实验结果表明（ＷＣ－Ｃｏ／ＮｉＣｒＢＳｉ）复合涂层磨损性能高于同配比     

Interface characteristics in cemented carbides with alternative binders

Cemented tungsten carbides with Co, Ni or Fe binders were studied by transmission electron microscopy. Particular attention was paid to phase and grain boundaries. A striking feature is the high frequency of coherent carbide/binder interfaces with Fe. The Fe rich binder adopts an epitaxy orientation relationship with prismatic facets of WC, with a parametric misfit of about 1.5%. A special orientation relationship with basal facets of WC grains is sometimes observed with Ni binder, as already noticed for Co. It is associated with a parametric misfit of about 15%. Binder segregation in WC grain boundaries was studied taking into account the effect of carbon content in the alloys. Whatever the binder, no influence of the carbon content could be pointed out. The analyses performed in random grain boundaries in WC-Co alloys agree with the literature value of 0.5 monolayer of segregated Co while slightly larger values are obtained for Ni and Fe binder. ∑ = 2 special grain boundaries were studied in WC-Co and WC-Ni alloys and no segregation was detected. The higher grain boundary segregation as well as the occurrence of coherent interfaces should influence the mechanical properties of WC-Fe alloys.     

Carbide grain growth in cemented carbides sintered with alternative binders

Cemented carbides are composites made of a hard refractory ceramic phase and a ductile binder, most commonly WC and Co, respectively. Since the use of cobalt in the hard metal industry is questioned by the new European regulation on chemicals, extensive research has been done to develop new grades based on a Co-Ni-Fe binder. With similar mechanical, physical properties and affinity to C and W, nickel and iron are the best candidates for an efficient binder in cemented carbides. As mechanical properties are strongly dependent on the materials microstructure, and especially on the WC grain size, understanding the effect of the binder on the final microstructure is crucial.In this work, the carbide grain growth behaviour of WC-M alloys (M = Co, Ni, Fe) with different carbon contents is discussed from qualitative and quantitative microstructural analyses. Whereas grain growth is more or less inhibited in WC-Fe alloys, increasing carbon content promotes grain growth in WC-Co and WC-Ni alloys, with a slight abnormal grain growth in case of Ni binder. Different mechanisms for grain growth are discussed, in relation with the observed morphology of WC grains after sintering.     

Diffusion parameters of grain-growth inhibitors in WC based hardmetals with Co,Fe/Ni and Fe/Co/Ni binder alloys

The diffusion behaviour of the grain-growth inhibitors (GGI) Cr and V during early sintering stages from 950 to 1150 °C was investigated by means of diffusion couples of the type WC-GGI-binder/WC-binder. Besides Co, also alternative Fe/Ni and Fe/Co/Ni binder alloys were investigated. It was found that the diffusion in green bodies differs significantly from sintered hardmetals. Diffusivities in the binder phase were determined from diffusion couples prepared from model alloys and were found to be almost equal for Co and alternative binder alloys. The diffusion parameters determined from green bodies allowed to estimate the GGI distribution in a hardmetal during heat up. This was subsequently used to estimate an appropriate grain size of VC and Cr₃C₂ in hardmetals, which is required to ensure a sufficient GGI distribution during sintering before WC grain-growth initiates.     

Effects of Ni addition and cyclic sintering on microstructure and mechanical properties of coarse grained WC–10Co cemented carbides

Coarse grained WC–10(Co, Ni) cemented carbides with different Ni contents were fabricated by sintering-HIP and cyclic sintering at 1450 °C. The effects of Ni addition and cyclic sintering on the microstructures, magnetic behavior and mechanical properties of coarse grained WC–10(Co, Ni) cemented carbides have been investigated using scanning electron microscope (SEM), magnetic performances tests and mechanical properties tests, respectively. The results showed that the mean grain size of hardmetals increases from 3.8 μm to 5.78 μm, and the shape factor Pwc decreases from 0.72 to 0.54, with the Ni content increases from 0 to 6 wt.%. Moreover, the W solubility reaches the highest value of 10.33 wt.% when the Ni content is 2 wt.%. The hardness and transverse rupture strength of WC–8Co–2Ni are 1105 HV₃₀ and 2778 MPa, respectively. The cyclic sintering is conducive to increase the WC grain size of WC–10(Co, Ni) and improves the transverse rupture strength of WC–10Co without compromising the hardness of alloys.     

Phase formation in cemented carbides prepared from WC and stainless steel powder – An experimental study combined with thermodynamic calculations

Cemented carbides prepared from mixes of WC and stainless steel powder have been proposed as possible alternatives to WC-Co. However, phase formation in such systems is not well described in the literature, in particular with regard to the possible formation of Cr-carbides. In this work, cemented carbides have been prepared from batches of coarse WC powder and 20 wt% AISI 360 L stainless steel powder, considering different carbon black additions to vary the final carbon contents to 4.9, 5.64, 5.75 wt% C. Both experimental results and thermodynamic calculations show that no classical two phase area – containing only WC and metallic binder- can be expected in these alloys. (Cr, Fe)-carbides are observed at all carbon contents in equilibrium with eta phases and binder, and at the highest carbon content also with graphite. As a consequence of the formation of (Cr, Fe)-carbides the amount of metallic binder decreases significantly, and the composition of the binder changes drastically. The binder phase in the sintered materials constitute an Fe-15Ni alloy with about 5 wt% Cr and 2 wt% W in solid solution, which is more similar to a maraging steel rather than a stainless steel. Both thermodynamic calculations and experimental results confirm that the maximum amount of Cr that can be retained in the metallic binder is around 5 wt% Cr which implies that, after sintering, the stainless steel properties will be lost.     

Effect of Cu, Ni on the property and microstructure of ultrafine WC-10Co alloys by sinter-hipping

Sub-micron size (0.4-0.6 μm) Co-Cu/Ni composite powders were synthesized by a co-precipitation method. The effects of minor Cu and Ni additions on the microstructure and the mechanical properties of ultrafine WC-10Co alloys were investigated using scanning electron microscope, X-ray diffraction and mechanical properties tests. The results show that Co-Cu binder phase refines the WC grains and increases the hardness of the base alloys. But the addition of Ni can't refine the WC grains and increase the hardness. The addition of minor Cu or Ni can improve transverse rupture strength of alloys through the solid solution strengthening. However, adding excess Cu can lead to the decrease in transverse rupture strength. With the partial substitution of Co by Cu and Ni, the hardness and transverse rupture strength of the alloys have a little change.     

WC-Co-(Ni)-(Cr)硬质合金在中性溶液中的腐蚀行为

以WC粉、Co粉、Ni粉及Cr3C2粉为原料,采用粉末冶金方法制备了3组不同粘结相成分的WC-Co-(Ni)-(Cr)硬质合金,通过极化曲线测试和浸泡实验研究了3组合金在中性溶液中的腐蚀行为,并采用扫描电镜、能谱分析、X射线光电子能谱(XPS)和EBSD等手段对其腐蚀机理进行了探讨。结果表明,WC-Co和WC-Co-Cr硬质合金在中性溶液中主要发生粘结相Co的腐蚀,浸泡产生的腐蚀产物主要是Co(OH)2;添加Cr将提高WC-Co硬质合金在中性溶液中的耐腐蚀性能,这可能与Cr的添加明显降低了粘结相中密排六方Co的含量有关;同时添加Ni和Cr可进一步提高WC-Co合金在中性溶液中的耐腐蚀性能,在pH=7的Na2SO4溶液中浸泡480 h后,WC-Co-Ni-Cr合金发生很少量的腐蚀。     

Effects of fine WC particle size on the microstructure and mechanical properties of WC-8Co cemented carbides with dual-scale and dual-morphology WC grains

Dual-scale and dual-morphology WC grained WC-8Co cemented carbides comprising triangular or hexagonal fine WC grains and plate-like coarse WC grains were synthesized by vacuum sintering using Co, flaky graphite, WC, and coarse W as the starting materials. The effects of fine WC particle sizes on microstructure, relative densities, and mechanical properties of the dual-scale and dual-morphology WC grained cemented carbides were investigated. The results revealed that the growth of plate-like coarse WC grains was further promoted with the decrease in the particle size of the added fine WC; hence, their aspect ratio increased. In addition, added fine WC led to the separation of plate-like coarse WC grains so as to break their oriented arrangement and prevent their face contact; hence, plate-like coarse WC grains were completely covered by the Co binder phase. Moreover, the addition of smaller particle size of fine WC contributed to more uniform Co binder phase. When 0.4-μm WC powders was added, the aspect ratio of plate-like coarse WC grains was greater than that of plate-like WC grained cemented carbides without the addition of fine WC. The dual-scale and dual-morphology WC grained cemented carbides by adding 0.4-μm fine WC exhibited good comprehensive mechanical properties, with a transverse rupture strength of 3645 MPa, a Rockwell hardness of 91.5 HRA, and a fracture toughness of 12.3 MPa∙m^1/2.     

Investigations on kinetics of formation of fcc-free surface layers on cemented carbides with Fe-Ni-Co binders

The formation of surface layers free of face centered cubic (Ti,Ta,Nb,W)(C,N) carbonitrides and enriched in ductile binder phase (fcc-free surface layers) was investigated on cemented carbides containing Fe-Ni-Co binders. Cemented carbide alloys with varying Fe-Ni-Co binders were sintered in vacuum atmospheres at 1450 °C for 2, 3 and 5 h. Independent of the binder composition the growth of fcc-free surface layers obeys a parabolic law. For same sintering conditions, fcc-free layer growth kinetics is enhanced by the addition of Fe to Co and Ni binders. Thermodynamic calculations showed that adding Fe to Co and Ni binders increases the solubility of the element nitrogen in the liquid binder phase. The higher solubility of N in Fe-containing binder phases promotes the formation of larger fcc-free surface layers, so that the width of fcc-free surface layers can be modified by controlling the Fe content in the binder phase.     

Mechanical properties of WC–10Co cemented carbides sintered from nanocrystalline spray conversion processed powders

Mechanical properties and microstructures of nanocrystalline WC–10Co cemented carbides were investigated. The nanocrystalline WC–10Co cemented carbide powders were manufactured by reduction and carbonization of the nanocrystalline precursor powders which were prepared by spray drying process of solution containing ammonia meta-tungstate (AMT) and cobalt nitrate. The WC powders were about 100 nm in diameter mixed homogeneously with Co binder phase and were sintered at 1375 °C under a pressure of 1 mTorr. In order to compare the microstructures and mechanical properties with those of nanocrystalline WC–10Co, commercial WC powders in a diameter range of 0.57–4 μm were mixed with Co powders, and were sintered at the same conditions as those of nanocrystalline powders. TaC, Cr₃C₂ and VC of varying amount were added into nanocrystalline WC–10Co cemented carbides as grain growth inhibitors. To investigate the microstructure of Co binder phase in the WC–10Co cemented carbides, Co–W–C alloy was fabricated at the temperature of sintering process for the WC–10Co cemented carbides. The hardness of WC–10Co cemented carbides increased with decreasing WC grain size following a Hall–Petch-type relationship. The fracture toughness of WC–10Co cemented carbides increases with increasing HCP/FCC ratio of Co binder phase by HCP/FCC phase transformation.