不同粘结相WC基硬质合金微观结构与性能

以碳质量分数为理论含碳量的WC为硬质相，在1450℃下通过气压烧结制备WC-20Fe,WC-20Ni和WC-20Co硬质合金，通过X射线衍射、扫描电子显微镜、电子探针和力学性能测试研究了不同金属粘结相对烧结硬质合金微观结构和力学性能的影响。结果表明：WC-20Fe合金出现η脱碳相(Fe₃W₃C),W在粘结相Fe中的溶解度仅有1.915%(质量分数)，WC晶粒尺寸最小。WC-20Ni合金渗碳出现石墨相(C),W在粘结相Ni中的溶解度达到10.753%(质量分数)，WC晶粒尺寸最大，合金硬度最小。WC-20Co合金为正常两相区组织(WC+γ)，具有最高抗弯强度2720 MPa和最大硬度934.41 kg·mm^-2。所有合金断裂模式均为脆性断裂和沿晶断裂，WC-20Co合金断口出现明显的粘结相撕裂。     

Cr3C2含量对热压烧结WC基硬质合金材料微观组织和力学性能的影响

为了研制高强度高硬度的硬质合金刀具材料,本文采用真空热压烧结技术制备Cr₃C₂含量不同的WC基硬质合金。通过XRD、SEM、EDS等分析手段研究其物相组成及微观形貌,探究Cr₃C₂含量对WC基硬质合金力学性能和微观组织的影响规律。结果表明：在WC-Co硬质合金中添加适量Cr₃C₂可有效抑制WC晶粒异常长大,提高晶粒均匀度,减少微观组织缺陷,进而改善其综合力学性能。随Cr₃C₂含量增加,合金的硬度和抗弯强度先升高后降低,断裂韧性先降低后升高。当Cr₃C₂的质量分数为0.4%时,WC基硬质合金综合力学性能最佳,硬度(HV)达到20.97 GPa,抗弯强度为1 584 MPa,断裂韧性为10.92 MPa·m^1/2,其中硬度大幅提高对于硬质合金材料用作切削刀具具有重要意义。     

合金添加剂对WC基硬质合金氧化行为及其关联特性的影响

为了同步改善合金的高温抗氧化性能及物理与力学性能,设计WC-6Co-6Ni、WC-6Co-6Ni-1Cr₃C₂、WC-6Co-6Ni-1CeO₂和WC-12Co-1CeO₂等4组WC基硬质合金,分别对应1^#～4^#合金,对比研究合金的微观结构、物理与力学性能和700℃连续16 h的氧化行为。结果表明,CeO₂弥散相的存在不会导致WC基硬质合金强度降低,合金硬度遵循复合材料硬度及晶粒度和各相体积分数的耦合作用规律。4组合金中,4^#合金的硬度最高,其次为2^#合金,Co、Ni黏结金属对硬质合金硬度的影响显著。Cr₃C₂和CeO₂添加剂均可显著改善700℃下合金的抗氧化性能,但Cr₃C₂的改善效果明显优于CeO₂。在WC基硬质合金中添加适量的Cr₃C...     

V和Cr对超细WC-Co硬质合金Co粘结相成分与WC/Co界面组织结构的影响

采用粉末冶金法制备WC-30Co,WC-30Co-1VC和WC-30Co-1Cr3C2硬质合金(成分含量为质量分数,下同),分别采用随炉冷却和水淬2种方式进行冷却,采用电子探针分析技术和高分辨率透射电镜,分析合金的Co相成分以及WC/Co界面结构,研究V和Cr元素对WC-30Co合金的Co粘结相成分与WC/Co界面结构的影响。结果表明:VC抑制晶粒长大的效果比Cr3C2更明显;在1 280~1 360℃下烧结时,V和Cr的添加可提高W在Co相中的固溶量,而在1 400℃烧结时,对W在Co相中的固溶量影响不大。水淬态合金的WC/Co界面发现层状的含Cr和V的析出相,且含V析出相的厚度明显大于含Cr析出相的厚度;可以推断界面析出相是在烧结过程而并非冷却过程中形成的;析出相的形成是Cr3C2和VC抑制WC晶粒长大的重要原因。     

η相粉末的制备及烧结工艺对板状WC晶粒的影响

以W粉、Co粉及炭黑为原料制备η相粉末,向WC–10Co混合粉末中加入质量分数为8%的η相粉末和一定化学计量比的工业炭黑,利用传统粉末冶金工艺制备含板状WC晶粒的硬质合金。研究了合成温度对η相的影响以及烧结温度、固相烧结升温速率对板状WC晶粒的作用。结果表明:在氮气保护气氛下,当行星球磨时间为12 h时,1050℃保温1 h即可得到Co_6W_6C相含量较高的η相粉末。在保温时间为1 h的前提下,烧结温度为1440℃,有利于合金中板状WC晶粒的生长,此时合金的力学性能最佳;在烧结温度与保温时间一定的前提下,当固相升温速率由6℃/min降低到2℃/min时,板状WC晶粒的尺寸和长厚比逐渐增加,合金的强度保持不变,维氏硬度提高了3%,断裂韧性提高了13%。     

烧结方法对WC-Co硬质合金性能的影响

以原位还原碳化反应法制备的超细WC-Co复合粉为原料,分别采用放电等离子烧结、低压烧结和真空烧结工艺获得块体硬质合金,系统研究烧结方法对合金的显微组织、密度及力学性能的影响。结果表明:放电等离子烧结的合金中,主相为WC和Co,有少量η相(Co6W6C),低压烧结和真空烧结获得的合金中物相为WC和Co;所用3种不同的烧结方法均能获得细晶块体硬质合金,其中放电等离子烧结的晶粒最细为0.35μm;低压烧结合金具有优异的综合性能,HV30为15 121 MPa,断裂韧性为13.6 MPa.m1/2,横向断裂强度为4 210 MPa。     

Cr3C2/CrN复合添加剂对非均匀结构硬质合金性能的影响

本文以粗、中、纳米颗粒WC为原料,采用粉末冶金方法制备了不同Cr₃C₂/CrN复合添加剂含量的WC-10%Co非均匀结构硬质合金,并研究了Cr₃C₂/CrN复合添加剂对硬质合金微观组织结构和性能的影响。结果表明：随着Cr₃C₂/CrN复合添加剂含量增加,WC晶粒被抑制效果越显著,合金硬度呈递增趋势,抗弯强度则先增加后减小。当Cr₃C₂/CrN复合添加剂含量为1%时,合金综合性能最佳,维氏硬度达到1270HV3,抗弯强度达到2880MPa。复合添加剂增强作用机理主要是因为复合添加剂溶解在液相Co中,降低了WC在Co相中的溶解度,减缓WC溶解-析出过程,抑制了WC晶粒聚晶和异常长大现象,并起到固溶强化和弥散强化的作用,有效提升了合金综合性能。     

碳含量对WC-9Ni-1Cr细晶硬质合金组织结构及性能的影响

通过添加W粉或C粉调整WC原料粉末的总碳含量(质量分数)为6.04%~6.16%,采用低压烧结法制备WC-9Ni-1Cr细晶硬质合金。采用光学金相显微镜、X射线衍射、扫描电镜等,研究碳含量对WC-9Ni-1Cr细晶硬质合金组织结构及性能的影响。结果表明:在WC-Ni系合金中添加适量的Cr元素,得到无磁WC-Ni硬质合金,并且其无磁特性不随合金中碳含量的变化而发生转变。WC粉末的总碳含量为6.04%~6.16%时WC-9Ni-1Cr细晶硬质合金为二相区的正常组织,只存在WC相和Ni相,没有石墨夹杂或η相;而且在此二相区范围内WC的碳含量变化对WC-9Ni-1Cr细晶硬质合金的耐腐蚀性没有明显影响。随WC粉末的碳含量增加,合金硬度(HRA)与密度都逐渐降低,但降低幅度较小,而合金的抗弯强度逐渐提高。碳含量由6.04%增加至6.16%时,抗弯强度由2 250 MPa提高到2 850 MPa,提高26.6%。     

放电等离子烧结制备无粘结相SiCw/WC硬质合金

以碳化硅晶须(SiC whiskers,SiC_w)作为增韧相,通过放电等离子烧结制备了无粘结相SiC_w/WC硬质合金。考察了放电等离子烧结温度及SiC_w添加量对SiC_w/WC硬质合金组织性能的影响。结果表明,采用放电等离子烧结在1800℃下可获得相对密度高于99%的WC烧结体,其维氏硬度和断裂韧性分别达到25.99 GPa和4.99 MPa·m^1/2。添加适量的SiC_w可以改善SiC_w/WC烧结性能和断裂韧性,在SiC_w的质量分数为0.6%时,断裂韧性达到6.80 MPa·m^1/2,当添加过量的SiC_w时,增韧效果减弱。     

WC-(Co-Al)硬质合金的研究

研究采用反应烧结制备以Co3 Al代Co作为粘结金属的硬质合金技术。对制得的硬质合金进行了组织结构的观察及性能测定。结果表明 ,铝的加入有助于烧结过程中WC晶粒的细化和均匀化 ,制得了WC晶粒均匀的超细硬质合金。与相同粘结剂含量的钴粘结硬质合金相比 ,在耐腐蚀和高温抗氧化性方面 ,Co Al硬质合金表现出明显的优异性能。研究发现 ,在烧结中由于发生Co Al的激烈化合反应而导致孔隙的形成。采用低压等静压烧结或烧结后进行低压等静压处理可降低孔隙度提高合金的力学性能     

Effects of applied pressure on the brazing of superplastic INCONEL 718 superalloy

A superplastic INCONEL 718 superalloy was brazed with a Ni-P and a Ni-Cr-P amorphous filler metal. The effects of applied pressure on the bonding strength, microhardness, and corrosion resistance were studied. The results showed that the brazements with Ni-Cr-P filler metal have higher bonding strength and better corrosion resistance than those with Ni-P filler metal using a conventional brazing method without applied pressure. When brazing was conducted under applied pressure, the bonding strength increased with applied pressure for the brazements with both filler metals. This was caused by a decrease of intermetallic phase through ejection of the liquid phase enriched with melting temperature depressants in the molten filler metals from the joint clearance. Corrosion tests show that these brazements failed at the brazed joint and at the grain boundaries in the region adjacent to the brazement.     

“双层金属布”硬质涂层耐磨性能的研究

对复合在钢基体上的WC-Ni-Fe-Co系“双层金属布”硬质涂层的相对耐磨系数ε进行了测定,对比耐磨件是HRC60的高速钢,实验采用磨粒磨损和摩擦磨损,实验结果表明WC-Ni-Fe-Co系“双层金属布”涂层耐磨性明显优于高速钢（HRC60）,涂层耐磨性主要与WC相含量有关。     

中间层成分对TP304H不锈钢瞬间液相连接的影响

 采用镍基、铁镍基和铁基3种中间层合金进行了TP304H不锈钢的瞬间液相(TLP)连接试验,利用电子探针和能谱分析了中间层成分对接头组织和成分的影响。结果表明,镍基接头组织为固溶体,接头区出现了跨界面晶粒。虽然接头拉伸断裂于焊缝处,但强度、塑性已达到母材水平。铁镍基接头组织与母材组织不同,元素扩散差,焊缝界限清晰,接头性能低。铁基接头组织与母材组织相同,成分连续均匀分布,实现了真正的TLP连接。挂管试验结果表明,铁基接头不仅具有很好的强度和塑性,而且接头抗腐蚀性能好,可满足实际工业应用。     

Effect of Intermetallic Compounds on Microstructure and Mechanical Properties of Hot Roll Bonding Titanium to Steel

Titanium cladding on steel leads to the creation of properties such as resistance to corrosion that contribute to a widespread application of this metal composite in industries such as nuclear, chemical, aerospace, and biomaterial. One of the solid-state bonding methods to apply such a clad is to use the roll bonding method. In this paper, quality of the titanium cladded on carbon steel was studied in terms of metallurgical, mechanical properties and the effect of the copper interlayer on the metallurgical properties of bonding. The interface between the clad and the base metal was studied using a scanning electron microscope and light microscope and the phases formed were identified by X-ray diffraction analysis. The results showed that an increase in the bonding temperature increased the thickness of the intermetallic compounds, increased the hardness at close distances to the interface, and reduced the adhesion of the titanium cladded to the base metal.     

热喷涂WC-MoB-Co金属陶瓷涂层的耐腐蚀性能研究

本文采用团聚烧结法制备了WC-MoB-Co金属陶瓷喷涂粉末,使用超音速火焰喷涂技术在316L不锈钢基材上制备了WC-MoB-Co涂层;采用SEM、XRD表征了WC-MoB-Co粉末和腐蚀前后涂层的微观形貌及物相组成;测试了WC-MoB-Co涂层耐熔融锌铝腐蚀性能。研究结果表明,制备的WC-MoB-Co金属陶瓷复合粉末粒度集中、流动性好、松装密度高;WC-MoB-Co涂层结合强度高、孔隙率低;WC-MoB-Co涂层具有良好的耐腐蚀性能,随着腐蚀时间的延长,涂层中的WC颗粒逐渐参与反应。     

Investigating the Effect of WC on the Hardness and Wear Behaviour of Surface Modified AA 6063

The objective of this work is to reinforce Tungsten Carbide (WC) onto the surface of AA 6063 aluminium alloy using Gas Tungsten Arc (GTA) as heat source and investigate the hardness and wear properties. Based on number of trials, optimum GTA heat source parameters are finalized with reference to the proper fusion of base metal. It is found that the hardness is reduced after the application of heat. After the reinforcement of WC, the hardness returns back to the base metal value. In order to further to improve the properties, the reinforced alloy is heat Treated. The Microhardness of the reinforced and aged AA 6063 is increased by 50% with respect to base metal. The wear resistance of the reinforced surface is improved by 52% with respect to base metal. Characterization techniques like SEM, EDX and XRD are done and the presence of WC is confirmed.     

真空液相烧结法制备三元硼化物硬质合金覆层材料

采用液相烧结法在钢基体表面制备三元硼化物硬质合金覆层,将三元硼化物硬质合金的优异性能赋予钢基体表面,获得了耐磨抗蚀、界面结合强度高的新型硬质覆层材料。同时确定了硬质合金覆层的化学配比(B、Fe、Mo元素成分的配比)和C、Cr、Ni合金元素的添加量。对硬质合金覆层的洛氏硬度的测量结果表明,覆层的硬度明显高于钢基体的硬度,其中5Cr2Ni0.8C材料试样的硬度最大;对硬质合金覆层以及覆层与钢基体的界面结合处的扫描电镜观察和能谱分析表明,铬加入后部分进入陶瓷硬质相,加强了其硬度,而镍元素只在铁基粘结相中存在,并且覆层与钢基体之间形成了致密的冶金结合。     

In vitro genotoxic effects of hard metal particles assessed by alkaline single cell gel and elution assays

Hard metals (WC-Co) are made of a mixture of cobalt metal (Co, 5-10%) and tungsten carbide particles (WC, >80%). Excessive inhalation of WC-Co is associated with the occurrence of different lung diseases including an excess of lung cancers. The elective toxicity of hard metal is based on a physico-chemical interaction between cobalt metal and tungsten carbide particles to produce activated oxygen species. The aim of the present study was to assess the genotoxic activity of hard metal particles as compared with Co and WC alone. In human peripheral lymphocytes incubated with Co or WC-Co, a dose- and time-dependent increased production of DNA single strand breaks (ssb) was evidenced by alkaline single cell gel electrophoresis (SCGE) and modified alkaline elution (AE) assays. Addition of 1 M formate, a hydroxyl radical scavenger, had a protective effect against the production of ssb by both WC-Co or Co alone. On the basis of an equivalent cobalt-content, WC-Co produced significantly more ssb than Co. WC alone did not produce DNA ssb detectable by the AE assay, but results obtained with the SCGE assay may suggest that it either allows some uncoiling of the chromatin loops or induces the formation of slowly migrating fragments. Overall, this in vitro study is the first demonstration of the clastogenic property of cobalt metal-containing dusts. The results are consistent with the implication of an increased production of hydroxyl radicals when Co is mixed with WC particles. The SCGE results also suggest that WC may modify the structure of the chromatin, leading to an increased DNA sensitivity to clastogenic effects. Both mechanisms are not mutually exclusive and may concurrently contribute to the greater clastogenic activity of WC-Co dust. This property of WC-Co particles may account for the excess of lung cancers observed in hard metal workers.     

Corrosion Behavior of Welded Joints for Cargo Oil Tanks of Crude Oil Carrier

E32 grade corrosion resistant steel was welded with welding wires with three different S contents.The mi-crostructure,mechanical properties,inclusions,and corrosion behavior of welded joint were investigated.The joint coupon corrosion test and potentiodynamic polarization test were carried out under the simulated corrosion environ-ment of the inner bottom plates of cargo oil tanks.The pitting initiation and propagation mechanism of the weld metal were studied by scanning electron microscopy and infinite focus.The results indicated that the microstructures of three kinds of weld metals are all composed of acicular ferrite,ferrite side-plate and proeutectoid ferrite.The micro-structure of heat-affected zone is composed predominantly of bainite.Joint welded with low S filler wire has good me-chanical properties.S can decrease free corrosion potential and increase the corrosion tendency.The pitting initiation is oxide inclusion or sulfide-oxide inclusion complex.S can induce the formation of occluded area and promote the corrosion propagation.The chemical compositions of weld metal is similar to base metal,which can limit the galvanic corrosion between weld metal and base metal,and avoid formation of corrosion step.     

高质量低钴矿用硬质合金的研制和生产

运用矿用硬质合金非均匀结构的理论，以优质、结晶完整的ＷＣ粉和高纯细的的钴粉为原材料，利用先进的烧结等静压设备，采用“正碳烧结”和高压热等静压工艺，成功地研制和生产出了含钴６％的高质量矿用硬质合金。经现场使用，效果良好，其质量基本达到山特维克矿用硬质合金水平．并已投入大批量生产。