WC碳量对WC-6%Ni硬质合金组织与性能影响

选用总碳含量为5.90%（不饱和碳,质量分数,下同）和6.15%（饱和碳）两种WC原料,分别配制WC-6%Ni硬质合金的橡胶混合料和石蜡混合料并压制成压坯,通过调整压坯的脱胶和脱蜡条件来改变合金的相对磁饱和,使合金具有二相（WC+Ni）或三相（WC+Ni+η和WC+Ni+C）结构,对比研究了在相对磁饱相当的状态下,不饱和碳化钨原料和饱和碳化钨原料对WC-6%Ni硬质合金的组织结构与性能的差异。结果表明：WC-Ni硬质合金的比饱和磁化强度较低,但仍然和WC-Co硬质合金类似可以作为衡量合金碳含量高低的指标,其极限相对磁饱和值约为90%左右;不饱和碳化钨原料由于W2C相的存在,制得的合金组织受碳含量影响敏感,极易出现异常粗大晶粒的情况;在无磁状态、且处于二相结构时,不饱和碳化钨原料制得合金的密度、硬度、抗弯强度都稍高于饱和碳化钨原料制得合金;在相对磁饱和约80%、且处于二相结构时,不饱和碳化钨原料制得合金的密度、硬度稍高于饱和碳化钨原料制得合金,但饱和碳化钨原料制得合金的抗弯强度比不饱和碳化钨原料制得合金高19.4%。生产实践中,应选用饱和碳的碳化钨原料生产WC-Ni硬质合金以获得均匀的组...     

VC/Cr_3C_2及配碳量对WC-0.5Co超细硬质合金组织与性能的影响

以超细WC粉末和超细WC-6Co复合粉末为原料,添加VC/Cr3C2作为晶粒长大抑制剂,同时进行配碳,采用高能球磨和气压强化烧结制备晶粒度小于0.5μm的WC-0.5Co超细硬质合金,研究了不同VC/Cr3C2添加量及配碳量对其组织与性能的影响。结果表明:VC/Cr3C2有效抑制了烧结过程中WC晶粒的长大,显著提高了WC-0.5Co超细硬质合金的硬度。当VC/Cr3C2添加量为0.73%(质量分数,下同)时,合金的硬度(HV0.05)最高,达到32 658 MPa;同时一定的配碳量有利于控制合金中的脱碳,提高合金性能,当配碳量为0.2%时,WC-0.5Co-0.73VC/Cr3C2合金的综合力学性能最好,断裂韧性为6.935 MPa·m1/2,维氏硬度(HV0.05)为32 216 MPa。     

两相WC-Ni系硬质合金成份的评估原理

探讨了两相 WC- Ni系硬质合金的成分、相含量同合金密度 d及比饱和磁化强度 4πσ的定量关系 ,并将这些关系归因于γ相 (镍基 Ni- W- C固溶体 )成分 (钨和碳在γ相中的固溶度 )的影响。得到了相应于 WC- Ni系合金材料处于 WC+γ两相区上、下限成分和消磁 (4πσ=0 )成分的密度求值公式。论述了评估两相 WC- Ni系硬质合金成分的原理。     

WC-Ni硬质合金游离碳的无损测定原理

以三相 WC+ γ+石墨合金中各相含量同合金密度 d和比饱和磁化强度 4πσ的定量关系为基础 ,论述了用 d和 4πσ无损测定 WC- Ni系高碳硬质合金的游离碳的原理。用密度测定时的精度 (相对误差 )为 4‰ ,用比饱和磁化强度测定时的精度为 1%。     

超细硬质合金WC-8Co-0.8(Cr_3C_2/TaC)的组织与性能

以超细WC-8Co硬质合金为研究对象,混合添加晶粒长大抑制剂Cr3C2/TaC。结果表明,合金在添加0.8wt%Cr3C2/TaC时的TRS达到3675MPa,而在添加0.5wt%和1.0wt%Cr3C2/TaC时的TRS降到2120MPa;Cr3C2/TaC在很大程度上影响了合金烧结时的致密化,WC-8Co-0.8wt%(Cr3C2/TaC)压坯在1400℃下完全致密化需要的烧结时间为60分钟;而同类普通WC-8Co-0.8wt%(Cr3C2/TaC)的压坯,由于没有超细粉末的高表面能,烧结60分钟后密度只能达到理论密度的98.8%;TaC和Cr3C2对W在γ相中的固溶度具有相反的作用。     

Ni含量对粗晶WC-Co-Ni硬质合金组织和性能的影响

以WC-10%(Co+Ni)硬质合金为研究对象,在相同含量的Co+Ni粘结相中采用不同的钴镍比来研究Ni含量对WC-Co-Ni硬质合金组织和性能的影响。结果表明随Co+Ni粘结相中的镍含量的增加,合金中显微组织结构中的粘结相的分布均匀性变差;WC晶粒的尺寸和圆度增大。合金的强度性能结果表明WC-(Co+Ni)硬质合金在粘结相质量分数为60%Co-40%Ni时抗弯强度出现最大值;随Ni含量的增加,WC-(Co+Ni)硬质合金的硬度值相差不大,但呈下降趋势;合金的密度几乎没有变化;合金的钴磁降低,磁力呈现先增后降。     

铬的添加量对WC-9Ni硬质合金微观结构与性能的影响

以WC、Ni及Cr粉末为原料,采用传统粉末冶金方法制备了WC-9Ni-x Cr系列硬质合金。利用扫描电镜、X射线衍射仪、机械性能检测设备和浸泡腐蚀测试方法等观察和表征了试样的微观结构、物理机械性能和耐浸泡腐蚀性能。结果表明:Cr的添加量对WC-9Ni硬质合金的微观结构与性能有着显著地影响。微量的Cr添加后,合金的WC晶粒长大被抑制,晶粒尺寸出现下降;同时,合金的密度、抗弯强度下降,而硬度和耐中性水浸泡腐蚀性能(根据国际标准BS:6920:2000)得到提升。随着Cr添加量的进一步增加,合金的晶粒尺寸、密度、硬度、强度和耐腐蚀性能等变化趋势放缓。另外,根据XRD、SEM和EDX等检测结果发现:过量的Cr粉添加后,WC-9Ni硬质合金的结构中倾向于形成一种新相—(Wx,Cr(1-x))2C,这种新相易成为合金的断裂源。综合合金的微观结构和各项性能检测分析认为:当Cr粉添加量为1.2%(质量分数)时,WC-9Ni硬质合金具有相对最佳的综合性能。     

VC/Cr_3C_2添加剂对超细硬质合金组织及性能的影响(英文)

研究了VC/Cr3C2添加剂对WC-12Co超细硬质合金的显微组织、硬度和抗弯强度(TRS)的影响.结果表明,舍一定比例VC/Cr3C2添加剂的合金具有更均匀的微观组织和优异的力学性能.当添加剂含量(质量分数)为0.5%VC/0.2%Cr3C2时,1430℃烧结制备的WC-12Co超细硬质合金的抗弯强度达3786 MPa,硬度达91.7 HRA.VC添加剂对WC晶粒的连续长大和非连续长大的抑制作用比Cr3C2添加剂更有效.此外,当烧结温度较高时,VC/Cr3C2添加剂对WC晶粒长大的抑制效果更显著.VC和Cr3C2添加剂抑制WC晶粒长大的作用机理为:VC和Cr3C2添加剂降低了WC相在粘结相中的过饱和度,从而降低烧结温度下粘结相中WC相溶解-析出过程的驱动力,起到阻碍WC晶粒长大的作用.     

稀土Y_2O_3对WC-6%Co超细硬质合金组织及性能的影响

本文研究了在复合抑制剂(Cr3C2/VC/TaC)组成及含量不变的基础上,添加不同量Y2O3对WC-6%Co超细硬质合金的组织结构、磁性能及力学性能的影响。通过XRD以及性能测试,研究发现:在WC-6%Co超细硬质合金中添加Y2O3,能起到细化晶粒的效果,当添加0.2%Y2O3时,合金的晶粒最细,致密度最好,WC晶粒分布均匀;Y2O3会影响WC-6%Co超细硬质合金的磁性能,随着Y2O3含量的增加,合金的矫顽磁力增加,磁饱和强度略有降低,Y2O3能有效的改善合金的机械性能,特别是其抗弯强度。结果表明,当抑制剂配方为0.8%(Cr3C2/VC/TaC)+0.2%Y2O3时,制备的WC-6%Co超细硬质合金的机械性能具有最佳值,硬度达到94.1 HRA,抗弯强度1 770 MPa。     

关于纯Ni、纯Co及WC-Co硬质合金比饱和磁化强度值探讨(Ⅱ)

对纯Ni、纯Co及WC-Co硬质合金比饱和磁化强度值的有关文献作了进一步研究,发现某些作者的比饱和磁化强度值σ(以A·m~2/kg为单位)约为正常值的4π倍,对此做了初步分析。     

Spark plasma sinterability and dry sliding-wear resistance of WC densified with Co,Co+Ni,and Co+Ni+Cr

The spark plasma sinterability and the dry sliding-wear resistance of ultrafine-grained WC densified with ~16.7 vol% of Co, Co+Ni, and Co+Ni+Cr, compositions equivalent to that of the typical WC-10wt.%Co, were investigated and compared critically. Firstly, it was found that the partial substitutions of Co by Ni or by Ni+Cr are detrimental for the pressureless ultrafast sinterability, but much more in the latter than the former case, attributable to the higher eutectic temperatures during liquid-phase sintering. However, it was also observed that, thanks to the auxiliary stress supplementing the sintering stresses, the ultrafast sinterability with pressure is affected by these partial substitutions either not at all (Co by Ni) or very little (Co by Ni+Cr), making it possible in all cases to obtain fully-dense WC cermets with almost no grain growth at the same spark plasma sintering temperature. And secondly, it was found that these cemented carbides are very resistant to dry sliding wear, but that WC-(Co+Ni+Cr) is markedly more so, attributable essentially to its greater hardness. This is due to wear occurring essentially by two-body abrasion dominated by plastic deformation (ploughing), plus some oxidative wear with formation of tribo-oxidation layers that, although not entirely coherent, are nonetheless beneficial for the wear resistance.     

Optimization of Initial WC Grain-Size Distribution in WC-6Ni Cemented Carbides

The initial WC grain-size distribution, as one of the most important factors influencing the properties of alloys, has been focused on for a long time in some fields other than cemented carbides. In the present work, five groups of WC-6Ni cemented carbides were prepared and the effect of initial WC grain-size distribution on the microstructure and properties of the hard alloys was studied. The results indicate that initial WC grain-size distribution has significant influence on the microstructure and properties of WC-6Ni cemented carbides, except density. When the mass ratio of coarse-WC and fine-WC is 7:3, WC-6Ni cemented carbide samples with initial WC grain-size distribution of WC-1(4.8 μm) and WC-4(0.7 μm) show a relatively good combination properties, while the cemented carbide samples with WC-5(0.4 μm) as the fine-WC component exhibit higher values on some properties, mainly hardness and immersion corrosion resistance in acid and alkali.     

W+Co+C(碳黑)制备板状晶硬质合金及其性能研究

采用经球磨扁平化处理的W粉末为原料,添加适量Co、C(碳黑)、成型剂及纳米W粉制备板状晶硬质合金,研究了烧结温度、时间和添加纳米W粉,对板状晶硬质合金显微组织结构和性能的影响。结果表明,球磨预处理中颗粒W粉末可获得扁平化程度高的薄片状W粉末,以其为原料制备的WC-12%Co(质量分数)板状晶合金相对密度达97%,合金硬度呈现出明显的各向异性;添加纳米W粉或提高烧结温度、延长烧结时间,均有利于压坯烧结收缩致密化,生成更多的板状WC晶粒。     

Role of Co Content on Densification and Microstructure of WC–Co Cemented Carbides Prepared by Selective Laser Melting

WC–Co cemented carbides, well-known as the conventional tooling materials, have not been successfully produced by one step additive manufacturing processes such as selective laser melting(SLM) yet. The microstructure evolution as well as WC grain growth behavior has rarely been investigated in detail during SLM process. In this study, the WC–Co cemented carbides with different Co contents(12–32 wt%) were prepared by optimized SLM processes for comparative investigation of densification behavior, microstructure characterization and mechanical property. The increase in Co content in feedstock carbide granules can improve the densification behavior during SLM process. The SLM processed WC-12 Co shows larger average WC grain size and higher percentage of coarser WC grains as compared with both WC-20 Co and WC-32 Co. The microstructure characterization, combined with finite element simulation, shows the WC grain growth mechanisms include agglomeration and dissolution-deposition of WC during SLM process and agglomeration of WC is an important mechanism especially for WC–Co cemented carbides with Co content as low as 12 wt%. The comparison between horizontal(perpendicular to the SLM laser beam) and vertical(parallel to the SLM laser beam) cross sections of carbides shows that SLM process introduces a certain degree of microstructure and mechanical behavior anisotropy for WC-12 Co, WC-20 Co, and WC-32 Co.     

超细硬质合金WC-10Co-0.8(VC/Cr_3C_2)的烧结特征

超细硬质合金粉末粒度细小,具有高的比表面积和缺陷密度,因而具有较高的烧结活性,呈现出与普通硬质合金不同的烧结特征。因此,针对超细硬质合金特点制定合适的烧结工艺在生产超细硬质合金中是至关重要的。真空烧结超细硬质合金WC-10Co-0.8(VC/Cr3C2)的结果表明:1320℃烧结温度下的超细硬质合金,较1350℃和1380℃的密度和硬度低,WC晶粒细而孔隙度高。1350℃比1380℃具有更高的横向断裂强度(TRS)。WC-10Co-0.8(VC/Cr3C2)超细硬质合金的适宜烧结温度为1350℃。差热分析(DTA)对烧结过程中的热效应分析表明:出现液相温度为950℃,1300℃结束。同时氧化杂质被还原导致质量的损失和气体的产生。晶粒长大抑制剂VC和Cr3C2的加入,提高了氧化物杂质还原温度。     

钎料对YG8合金与低碳钢焊接性能的影响

采用两种铜基钎料HL841(CuZnMnSnNiCo合金)和HL105(CuZnMn合金)对YG8硬质合金和低碳钢进行真空钎焊,并对比研究了焊缝的微观组织、元素扩散情况及接头抗拉强度。研究表明:两种钎料与硬质合金结合处形成互溶区,HL105形成的互溶区宽度大概为1μm,而HL841形成的互溶区宽度约为3μm;HL841钎料中的Co、Ni等元素有利于形成Fe-Co-Ni单相固溶体,同时钎焊过程中钎料中的Co还能缓解硬质合金中粘结相Co的扩散流失。这些原因使得采用HL841焊接的试样的接头力学性能优于HL105。     

Cr_3C_2对WC-6.5％Co硬质合金组织和性能的影响

通过向WC-6.5%Co硬质合金中添加0%～2.0%的晶粒长大抑制剂Cr_3C_2,研究了其对硬质合金组织和力学性能的影响。研究结果表明,Cr_3C_2的添加细化了WC晶粒,但不能完全抑制WC晶粒的异常长大。Cr_3C_2使合金的硬度提高,但是却降低了合金的致密度和抗弯强度。Cr_3C_2添加量为0.5%时,合金的综合性能最好。     

碳量及B类孔隙对WC-8%Co硬质合金抗弯强度的影响

采用粉末冶金方法制备了WC-8%Co硬质合金试样,经氢气烧结后,利用钴磁测试仪、强度测试仪、电子显微镜和金相显微镜分别对试样的钴磁和抗弯强度进行测定、对试样断口和金相缺陷进行观察。研究了WC-8%Co硬质合金抗弯强度与碳量(相对磁饱和)、金相缺陷(B类孔隙)之间的关系。结果表明:将试样碳含量及孔隙度控制在一定的范围内,可以使试样抗弯强度保持在较高的水平,当试样相对磁饱和为88%~92%,B类孔隙为B00时,合金显微组织中WC晶粒较为均匀,无异常长大情况,WC-8%Co硬质合金抗弯强度可达3 286 N/mm2;同时,抗弯强度值的大小随孔隙度的增多而下降。另外,氢气烧结后经HIP处理可以有效消除WC-8%Co硬质合金中的孔隙缺陷,从而提高合金抗弯强度,经HIP处理的试样的强度比正常样的强度高出2.3%。