钼钨合金的生产工艺和性能

1 前言随着工业的发展,高熔点金属钼钨合金的研究及应用引起了人们的重视,目前已生产的钼钨合金有 M-30W-0.02C,Mo-25W-0.1Zr-0.05C,Mo-50W-1.25Ti-0.3Zr-0.15C等,部分性能见图1,图2。由于 Mo-30W 合金有比纯钼好得多的强度、硬度和耐蚀性能,在宇航、冶金等部门得到广泛地应用。     

Mo-30W钼合金棒材再结晶行为研究

采用粉末冶金工艺制备了Mo-30W钼合金棒材, 通过拉伸力学性能测试、硬度测试、光学显微镜(optical microscope, OM)、扫描电子显微镜(scanning electron microscope, SEM) 及能量色散谱仪(energy dispersive spectrometer, EDS) 等测试分析手段, 研究了Mo-30W钼合金棒材的再结晶行为。结果表明, 由于W的固溶强化和变形强化, Mo-30W钼合金棒材在1600℃高温抗拉强度达到170MPa, 延伸率为10%, 高温力学性能得到明显提升; 在1300~1500℃范围内, 随着温度的升高, Mo-30W钼合金棒材强度和硬度先保持稳定然后显著下降; 在1500℃时, Mo-30W钼合金棒材发生了完全再结晶, 抗拉强度为385 MPa, 维氏硬度为HV10 185, 抗拉强度和硬度值达到最低。     

钨12型高速钢的研究

本文在研究高速钢中合金元素配比对钢的组织和性能影响的基础上,提出了钨12钼2铬4钒稀土高速钢(简称W12R)。W12R符合我国资源特点,仍以钨为主。配合使用适量钼,提高了钢的强度、韧性,有利于钨系高速钢性能的改进,同时还可发挥返回料中残存钼的作用。钢锭成本与W18相当,但切削性能远超过后者;能达到高硬度水平,却保持良好的综合工艺性能。不同钨钼配比时,钨每增加2％,钼相应降低1％,则淬火温度可提高10℃左右。如淬火温度相同,则晶粒细化半级左右。高碳型高速钢在较低的奥氏体化温度时,晶粒比相同基体成分的通用型高速钢细;在较高的奥氏体化温度时,晶粒比通用型钢粗。使用钇稀土合金比加铈稀土1号合金所得低倍组织好。     

W质量分数对Mo-W合金组织结构与力学性能的影响

采用粉末冶金法制备含不同质量分数W(20%~80%)的Mo-W合金, 研究W含量对Mo-W合金组织结构与力学性能的影响。结果表明: 烧结过程中Mo与W相互扩散形成单相固溶体。W质量分数的增加能显著降低Mo-W合金的晶粒尺寸, 经1990℃烧结的Mo-80W合金晶粒尺寸比Mo-20W合金下降了46.5%。随W质量分数的增加, Mo-W合金的维氏硬度呈“双驼峰”形变化趋势, 在W质量分数为40%与60%处出现峰值。Mo-W合金的相对密度和抗拉强度随W质量分数的增加而下降, 抗拉强度最大值出现在烧结温度为1990℃的Mo-20W合金, 达到514.83 MPa; 随烧结温度的升高, 低W含量的Mo-W合金(W质量分数20%~40%)抗拉强度呈先上升后下降趋势, 而高W含量的Mo-W合金(W质量分数60%~80%)抗拉强度逐渐升高。Mo-W合金断裂方式为沿晶断裂与穿晶断裂相结合的混合模式。     

高密度钨合金研究现状与发展趋势

综合近年来国内外W—Ni—Fe，W—Ni—Cu，W—Cu等高密度钨合金及其材料的研究状况，介绍了有关钨合金方面的关键新技术，并且预测了今后钨合金材料的研究方向。     

球磨时间对钼钨合金粉物理性能及烧结特性的影响

本文采用球磨法制备了含30%钨的钼钨合金粉末,分析了不同球磨时间对钼钨合金粉的微观形貌、松装密度、费氏粒度等物理性能及烧结特性的影响。结果表明:随着球磨时间的延长,钼钨合金粉的颗粒团聚减少,松装密度增大,费氏粒度减小,烧结态相对密度增大。当球磨时间在20 h以上时,钼钨合金粉的颗粒分布均匀,松装密度增大至2. 07 g/cm~3以上,费氏粒度减少至3. 20μm以下,烧结态相对密度达到99%以上。     

W粉粒度对粉末温轧制备钨铜合金板组织和性能的影响

将不同粒度W粉分别和Cu粉混合均匀后,在100℃温轧成形获得钨铜生板坯。在1 350℃对生板坯进行液相烧结,获得钨铜合金板。研究了W粉粒度对钨铜生板坯密度和厚度的影响,探索了W粉粒度对烧结坯组织和性能的影响。结果表明:随着W粉粒度的增大,粉末温轧得到的钨铜生板坯的相对密度逐渐增大,厚度出现逐渐减小的变化趋势。W粉粒度越大,生板坯液相烧结后,获得的合金板坯的相对密度变化幅度越小,体积收缩率也越小。但W粉粒度越大,液相烧结过程中,W颗粒之间越难形成烧结颈,不利于生成金属W骨架,降低合金烧结板坯的力学性能。     

等离子钨、钼和钇共渗时钇原子对渗层的交互作用

利用双层辉光等离子渗金属技术,在20号钢表面进行钨-钼-钇和钨-钼共渗,并获得合金渗层。利用扫描电镜(SEM)和能谱仪(EDS)进行微观组织分析和成分分布检测,用X射线衍射仪(XRD)进行结构分析,用Fick第二扩散定律分别计算上述二元共渗和三元共渗渗层的钨、钼扩散系数以及扩散激活能。研究表明:钨-钼-钇和钨-钼共渗渗层组织均为柱状晶,渗层与基体之间有一条分界线。稀土钇的加入细化了渗层的组织;钨-钼-钇共渗层物相主要为:Fe(W,Mo,Y),Fe3Mo,Fe17Y2,W,Y等;钨-钼共渗渗层物相主要为:Fe(W,Mo);钇的加入使渗层中钼在距表面12~15,24~25,35~36μm处的扩散系数分别提高了1.72,1.85,2.10倍,平均增大1.89倍。而钨原子的扩散系数在加入稀土元素后减小了0.92,0.99,0.76,平均降低了0.89倍;稀土钇的加入降低了钼原子的扩散激活能,说明了稀土钇对钼具有催渗作用,但对钨没有催渗作用。     

钼合金、钨合金圆片

钼合金、钨合金圆片涉及一种电力半导体器件及电真空器件中的基片（俗称圆片）。主要是为解决现有的用钼制作的圆片只能制作普通的电力半导体器件及电真空器件。而用钨制作的圆片加工困难的问题而研制的。该发明的钼合金圆片是用钼钨合金或TZM合金或稀土钼合金制成的：钨合金圆片是用钨钼合金或钨钍合金或稀土钨合金或钨铼合金制成的。优点是加工比较容易，性能比现有的钼圆片优越，可用于制作高档的电力半导体器件及电真空器件。     

细晶Mo-18Cu合金烧结工艺的研究

采用溶胶-喷雾干燥-煅烧-氢还原方法制备了晶粒尺寸为30~50nm的超细Mo-18Cu复合粉末,并利用该复合粉末制备出了高性能细晶Mo-18Cu合金。研究了烧结工艺对烧结体致密化的影响、合金的力学性能和显微组织特征。结果表明:在1 350℃烧结,Mo-18Cu合金的相对密度可达98%以上,抗拉强度和伸长率分别达到545MPa和3.85%;合金的显微组织均匀,晶粒细小。     

梯度结构W(Mo)-Ni-Fe高密度合金的组织与结构

将93W-4.9Ni-2.1Fe混合粉末压坯经过脱脂预烧、渗钼和脱钼处理以及烧结,得到W(Mo)-Ni-Fe高密度合金,采用金相分析、能谱分析、显微硬度测试等方法对该合金的成分和微观结构进行分析.结果表明,W-Ni-Fe高密度合金经渗钥处理后形成显微组织、钼含量和镍铁粘结相的梯度分布,其特征是合金表层的粘结相少于芯部:...     

Nitrogenase phylogeny and the molybdenum dependence of nitrogen fixation in Methanococcus maripaludis

We studied the effects of molybdenum, vanadium, and tungsten on the diazotrophic growth of Methanococcus maripaludis. Mo stimulated growth, with a maximal response at 4.0 microM, while V had no effect at any concentration tested. W specifically inhibited diazotrophic growth in the presence of Mo. Coupling the results of our analysis and other known metal requirements with phylogenies derived from nifD and nifK genes revealed distinct clusters for Mo-, V-, and Fe-dinitrogenases and suggested that most methanogens also have molybdenum-type nitrogenases.     

The effects of MO and W on solidification of high speed steels

The effects of systematic variations in Mo content, W content, and the Mo:W ratio upon the freezing process and as-cast carbide morphology of high speed steels were studied for four series of alloys encompassing the nominal composition ranges of AISI type M2 (6 W-5 Mo-4Cr-2V-0.85C) and MIO (0W-8Mo-4Cr-2 V-0.85C) high speed steels. Thermal analysis, metallographic examination, and quantitative metallography were used to characterize these effects. The Hquidus, peritectic, and eutectic reactions were similarly influenced by molybdenum and tungsten, the peritectic temperature being strongly depressed by additions of either element. The types of carbides found in the as-cast structures did not vary, but the amount of feathery eutectic carbide (a layered structure of MC and M₆C) was directly relatedto the total Mo plus W content. The amount of isolated vanadium-rich MC type carbide was seen to increase as the amount of feathery eutectic decreased, and also varied with the Mo:W ratio.     

W4Mo2Cr4VNb钢的组织和力学性能

 由于钨、钼、钒合金元素价格昂贵,因而导致含较多这类合金元素的钢的成本较高。合理运用高速钢的合金化理论,研究出了一种低合金高速钢——W4Mo2Cr4VNb。此钢的(W+Mo+V)含量比通用高速钢W9低很多,而且通过调整碳含量及加入价格较便宜的微合金元素铌,使该钢具有较好的综合力学性能和较低的成本。文章研究了W4Mo2Cr4VNb钢的组织和力学性能。     

Interfacial reaction-controlled reprecipitation of W atoms in liquid matrix phase during the sintering of W-8 pct Mo-7 pct Ni-3 pct Fe

Microstructural evolution and variation in phase composition of W-8 pct Mo-7 pct Ni-3 pct Fe alloy were investigated with respect to various isothermal holding times, ranging from 5 to 240 minutes, at a sintering temperature of 1480 °C. Mass transfer was found to proceed actively in both the liquid matrix phase and the tungsten-based solid phase during the initial stage of the isothermal hold. Formation of large jagged grains was found to be a result of excessive interdiffusion between molybdenum and tungsten. The jagged grains gradually developed into spheroidal grains with the reprecipitation of supersaturated tungsten atoms in the liquid matrix phase, which also resulted in crystallization of the matrix phase with less lattice dilation during cooling. Based on model fitting, reprecipitation of tungsten atoms from the liquid matrix phase to grains is proposed to be controlled by a first-order interfacial reaction.     

Decomposition of ferrite in commercial superduplex stainless steel weld metals; microstructural transformations above 700 °C

The microstructural stability at temperatures above 700 °C of weld metal of type 29Cr-8Ni-2Mo-0.39N and weld metal of type 25Cr-10Ni-4Mo-0.28N has been compared. Multipass welding was employed using the gas tungsten arc welding technique with a shielding gas of Ar+2 pct N₂. The quantitative assessment of the intermetallic phase was performed using automatic image analysis in the light optical microscope (LOM). Detailed microanalysis was also performed using scanning and transmission electron microscopy. A computer program developed by the authors was used to calculate a continuous cooling-temperature (CCT) diagram on the basis of the experimentally determined time-temperature-transformation (TTT) diagram. Thermodynamic calculations for estimating phase stabilities and for interpreting experimental observations were performed. It was found that weld metal of type 29Cr-8Ni-2Mo-0.39N was microstructurally more stable than weld metal of type 25Cr-10Ni-4Mo-0.28N. A lower molybdenum concentration and a higher nitrogen concentration in the former alloy could explain the higher stability with respect to the intermetallic phase. The higher nitrogen concentration also provides a rationale for the higher stability against the formation of secondary austenite in weld metal of type 29Cr-8Ni-2Mo-0.39N. This effect, which is associated with a lower thermodynamic driving force for precipitation of secondary austenite during multipass welding, can be explained by nitrogen-enhanced primary austenite formation.     

Effect of molybdenum on the fracture characteristic of high-speed steel quenched matrix

The fractures of three model alloys, imitating by their chemical composition the matrixes of the quenched high-speed steels of various Mo: W relations were analyzed. According to the measurements of the stress intensity factor K_Ic and the differences in the precipitation processes of carbides it was found out that the higher fracture toughness of the matrix of the molybdenum high-speed steels than on the tungsten ones is the results of the differences in the kinetics of precipitation from the martensite matrix of these steels during tempering. After tempering at 250 and 650°C the percentage of the intergranular fracture increases with the increase of the relation of Mo to W in the model alloys of the high-speed steel matrix. This is probably the result of higher precipitation rate of the M₃C carbide (at 250°C) and the MC and M₆C carbides (at 650°C) in the privileged regions along the grain boundaries. The change of the character of the model alloy fractures after tempering at 450°C from the completely transgranular one in the tungsten alloy to the nearly completely intergranular one in the molybdenum alloy indicates that the coherent precipitation processes responsible for the secondary hardness effect in the tungsten matrix begin at a lower temperature than in the molybdenum matrix. After tempering for the maximum secondary hardness the matrix fractures of the high-speed steels reveal a transgranular character regardless the relation of Mo to W. The higher fracture toughness of the Mo matrix can be the result of the start of the coherent precipitation processes at a higher temperature and their intensity which can, respectively, influence the size of these precipitations, their shape and the degree of dispersion. The transgranular character of the fractures of the S 6-5-2 type high-speed steel in the whole range tempering temperatures results from the presence of the undissolved carbides which while cracking in the region of stress concentration can constitute flaws of critical size which form the path of easy cracking through the grains. The transgranular cracking of the matrix of the real high-speed steels does not change the adventageous influence of molybdenum upon their fracture toughness. On the other hand, the carbides, undissolved during austenitizing, whose size distribution in the molybdenum steels from the point of view of cracking mechanics seems to be unsatisfactory, influence significantly the fracture toughness of these steels.     

MA-SPS制备超细晶Ti-8Mo-3Fe合金的摩擦磨损性能

以机械合金化+放电等离子烧结（MA-SPS）制备的超细晶Ti-8Mo-3Fe合金为研究对象,研究了合金在模拟体液（SBF）中的摩擦磨损性能,并与放电等离子烧结制备的微米尺寸晶粒的Ti-8Mo-3Fe合金、铸造纯Ti及Ti-6Al-4V （TC4）合金进行了对比.结果表明:采用MA-SPS工艺可制备出高致密度、组织均匀的超细晶Ti-8Mo-3Fe合金,合金由β相及少量α相组成,平均晶粒尺寸为1.5 μm,显微硬度为448 HV;在相同摩擦磨损条件下,超细晶Ti-8Mo-3Fe合金的摩损程度明显低于微米晶粒Ti-8Mo-3Fe和铸态的纯Ti及TC4合金,具有最低的磨损体积和较稳定的摩擦系数.超细晶Ti-8Mo-3Fe合金的磨损机制为磨粒磨损,而微米晶粒Ti-8Mo-3Fe和铸态纯Ti及TC4合金的磨损机制为磨粒磨损和黏着磨损并存的混合磨损.      

以柠檬酸和过氧化氢为络合剂电感耦合等离子体原子发射光谱法测定选矿样品中钨和钼

以盐酸、硝酸、氢氟酸、硫酸、柠檬酸和过氧化氢溶解样品,选择W239.709 nm和Mo 284.823 nm的谱线分别作为钨和钼的分析线,用ICP-AES光谱法测定了样品中钨和钼含量。利用柠檬酸和过氧化氢与钨酸、钼酸络合作用,抑制钨酸和钼酸的析出,促使样品的快速溶解,确保了钨、钼测定结果的准确性。钨和钼的检出限分别为0.015 μg/mL 和0.003 μg/mL,测定下限分别为0.075 μg/mL和 0.015 μg/mL。当钨、钼含量分别在0.1~100 μg/mL范围内,其校准曲线均呈线性关系,且线性相关系数都在0.999 5以上。采用本方法测定钼矿石标准样品和选矿流程样品中钨、钼时,测定值与认定值或硫氰酸盐光度法或重量法的测定值相符。用钨矿石标准样品和选矿流程样品进行加标回收试验,测得钨的加标回收率在96%～105%之间,钼的加标回收率在94%～102%之间。