超细无立方相层梯度硬质合金的研究进展

综述了目前应用于涂层基体的无立方相层含氮功能梯度硬质合金的研究进展;详细介绍无立方相层的形成机理,无立方相层梯度合金烧结工艺的研究,无立方相层梯度合金中N元素添加方式的成果;评述了N含量以及组分对无立方相层的影响规律;提出深入研究N含量对超细无立方相层梯度硬质合金性能和结构的影响,以及深入研究烧结工艺参数是今后研究工作...     

采用不含氮原料制备脱β层梯度硬质合金的组织和成分

采用不含氮的硬质合金原料,在梯度烧结工艺前添加一步微压氮化烧结(氮气分压为0.5kPa)工艺,然后于1 420,1 450,1 480℃下烧结1h制备了脱β层梯度硬质合金;另在无微压烧结工艺下制备了均质结构硬质合金;分别采用SEM、XRD及EDS等分析了合金的组织、相组成及成分分布。结果表明:在上述微压烧结工艺下制备的梯度硬质合金中脱β层厚度分别为8,13,24μm;该脱β层梯度硬质合金的物相和成分分布规律与采用含氮硬质合金原料制备的基本一样,即脱β层中仅含WC及钴相,心部为WC、(Ti,W)C和钴相,脱β层中的钛元素含量基本为零,钴元素的含量高于心部的平均含量,钨元素含量的变化不大。     

梯度过渡层对异质树脂材料并联结构拉伸强度和延性的影响

选择弹性模量依次减小的7种树脂材料,利用多材料喷射打印技术制备由最大和最小弹性模量材料并联形成的具有4种界面结构的拉伸试样,界面结构分别为无过渡层、宽度3 mm均质过渡层(由弹性模量居中的1种材料组成)以及宽度分别为3,5 mm的梯度过渡层(由另外5种材料组成),分析了其界面成形质量及拉伸性能.结果表明:无过渡层试样的界面处存在纹道和较多孔洞,成形质量较差;添加均质过渡层后,界面缺陷减少,拉伸强度略微增大,但是断裂应变降低了14.8％;添加梯度过渡层后,界面成形质量进一步提高,拉伸强度略微增大,延性明显提高,含宽度3,5 mm梯度过渡层试样的断裂应变分别比无过渡层试样提高了10.6％,37.9％.     

铸造铝合金激光表面改性金属-陶瓷梯度层

利用5kW CO2横流激光器对铸造铝合金表面先后预置不同成分粉末进行两次激光辐照扫描，成功地制备了Ni/WC和Cr/WC表面改性梯度层，并运用XRD、EDXS和SEM方法对激光表面改性梯度层的组织结构进行观察分析。发现经第二次激光扫描过程后在激光改性梯度层中因合金元素之间的反应，产生了大量的金属间化合物，激光改性梯度层的组织除α－Al、Si和WC外，在Ni/WC激光改性梯度层中，金属间化 的主要为Al3Ni2和Ni3Al，Cr/WC激光改性梯度层的金属间化合物为Al9Cr4和Cr9Al17。另外，显微硬度测试表明，自基体至改性层表面激光改性梯度层内显微硬度呈现连续变化趋势，而单次激光表面合金化层在与革体的交界处存在硬度突变。     

梯度结构对氧化铝陶瓷涂层抗冲击载荷性能的影响

梯度结构陶瓷涂层以其优异的抗热震性表现出巨大的工程应用前景。为推动梯度陶瓷涂层在机械零件表面强化上的应用,采用“三明治”式梯度结构形式,建立镍基氧化铝梯度陶瓷涂层在冲击载荷作用下有限元模型,分析冲击载荷作用下涂层的力学性能,以及梯度层的结构形式、厚度及层数等参数对涂层的力学性能影响。结果表明：较无梯度结构陶瓷涂层相比,梯度结构能有效减缓涂层与基体结合面上的应力突变,涂层内部最大Mises应力明显降低,合理的梯度结构能改善涂层内部Mises应力分布,改变应力分布特征,减缓表面陶瓷涂层的冲击应力,从而防止陶瓷涂层在冲击载荷作用下脱落。最后对制备层状结构梯度陶瓷涂层时,如何进行梯度层结构设计进行了探讨,并提出了采用0.25次方幂指数梯度结构,得出10层中间层就可有效减缓冲击载何、降低Mises应力突变的结论。     

梯度聚晶金刚石复合材料的开发

应用粉末层铺法制备梯度聚晶金刚石复合片材料 ,并通过SEM、XRD、显微硬度等对该材料进行组织与性能分析。结果表明 ,在以钴作粘结剂的聚晶金刚石层中金刚石相实现了D D结合 ,通过梯度过渡层与硬质合金基体结合既保证了聚晶金刚石的硬度 ,又改善了界面的结合状况 ,从而提高了聚晶金刚石复合片的性能和使用寿命     

硬质合金刀具高能离子源增强多弧镀AlCrTiSiN梯度涂层制备及性能研究

采用离子源增强的多弧离子镀新技术,在硬质合金刀具表面制备了不同含Si层梯度结构的AlCrTiSiN梯度涂层,并对涂层组织结构、残余应力、结合强度、摩擦磨损以及铣削和钻削加工灰铸铁性能进行了详细的研究。结果表明：不同含Si层梯度结构的AlCrTiSiN涂层主要由固溶的(Al,Cr) N、(Al,Ti) N相和非晶态Si₃N₄相组成。其中,含Si层梯度变化最缓和的G3(Gradient 3)涂层具有较高的结合强度,较低的残余压应力、摩擦因数和磨损率。铣削和钻削试验显示,涂层刀具的切削磨损机理主要表现为磨粒磨损和粘着磨损。G3涂层降低了磨粒磨损,其刀具的铣削和钻削寿命均最高,这主要得益于其含Si层的梯度设计、适当的压应力(-3.8 GPa)以及良好的膜基结合强度。研究结果表明,通过对含Si层进行梯度设计可显著提高涂层刀具的切削性能。     

梯度聚晶金刚石复合片的耐热性能

在应用粉末层铺法制备梯度聚晶金刚石复合片（PDC）的基础上,用扫描电镜、热分析仪对其进行了微观组织观察和耐热性能测定。结果表明：以钴作粘结剂的聚晶金刚石层中金刚石相实现了金刚石-金刚石结合,通过梯度过渡层与硬质合金基体结合,既保证了聚晶金刚石的硬度,又改善了界面的结合状况;聚晶金刚石的耐热性比单晶金刚石有较大提高,并且其耐热性受到加热速度、环境气氛的影响。     

铜合金表面镍基渗层制备及在800 ℃的氧化行为

选用镍基合金粉末作为铸渗剂,利用负压铸渗工艺在铜合金表面制备了镍基渗层,用SEM、EDS、XRD对表面渗层的显微结构、成分变化以及相组成进行了分析;并研究了表面渗层在800 ℃的氧化行为.结果表明:渗层结构由表面烧结层、中间冶金熔合层和内层扩散层三层组成;渗层元素从表面到基体呈梯度变化;渗层表面氧化后生成了含有NiO、Cr2O3和NiCr2O4的致密氧化膜,氧化动力学曲线遵循抛物线规律,与基体相比抗氧化性能显著提高.     

硬质合金表面化学镀Ni-P-金刚石粉沉积金刚石膜的研究

利用直流等离子射流装置在以化学镀Ni-P-金刚石粉为过渡层的硬质合金上沉积金刚石薄膜。采用SEM、EDS和X射线衍射仪(XRD)初步探讨了金刚石薄膜的表面形貌和物相组成。结果表明硬质合金刀片表面化学镀Ni-P后沉积金刚石薄膜,金刚石成核密度小、晶形差,难以得到结晶质量良好的金刚石膜。而在硬质合金刀片表面化学镀Ni-P-金刚石粉后沉积金刚石薄膜,成核密度比较高,晶形多为(100),但结合力较差。     

缓冲层对硬质合金环与钢体钎焊接头残余应力的影响

采用有限元软件对硬质合金圆环与钢基体钎焊接头残余应力的分布状态进行模拟,研究缓冲层对接头残余应力的影响,结果表明, 在钎缝与硬质合金一侧接触面上残余应力最大,在接触面上靠近中心侧区域为最危险区域.通过添加缓冲层,可以大大缓解焊后的残余应力,且缓冲层的厚度存在最佳值.经试验验证,计算结果与试验基本一致.     

Effects of Co content and WC grain size on wear of WC cemented carbide

WC cemented carbides are used extensively to improve abrasion resistance. Co content and WC grain size influence the mechanical properties of the cemented carbides. In this study, the effects of Co content and WC grain size of cemented carbide on wear were examined. We prepared 13 different cemented carbides with different Co content and WC grain size. Wear tests were carried out against 0.45% carbon steel under dry condition at 98 N and 232 mm/s. From the results, we found that wear increased with both Co content and WC grain size. Specific wear rate of the cemented carbides tested was in the range of 10⁻⁷ mm³/(N m). We discussed the wear properties with hardness and the mean free path of the cemented carbide. These two parameters alone cannot explain the wear property.     

Resistance of a binderless cemented carbide to abrasion and particle erosion

A binderless cemented carbide has been evaluated in abrasion and erosion tests. The binderless carbide was compared with: SiC, Al₂O₃ and two conventional cemented carbides with 6% Co and different WC grain sizes (1 and 7 μm). In the abrasion tests, the materials were ground with silica, silicon carbide and diamond particles in the size range of 5–15 μm. The erosion tests were performed with 80, 200 and 600 μm silicon carbide erodents. The angle of impingement was 45° and the erodent velocity 70 m/s. In all tests, the conventional cemented carbides showed the highest, the binderless cemented carbide an intermediate and the ceramics the lowest wear resistance. Scanning electron and atomic force microscopy of the abraded surfaces revealed that the binderless cemented carbide was worn by a preferential removal of TiC grains. In erosion, the wear mechanism was largely plastic for the cemented carbides, whereas the ceramics were worn by micro-fracture. The SEM analysis also showed an impact scaling effect for the cemented carbides in erosion. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparison of the wear resistance of selected steels and cemented carbide cutting tool materials in machining wood

An experimental investigation is described where specimens of selected steels and cemented carbides are tested to simulate cutting green wood and cured wood. Extensive results are presented that show quantitatively the progressive wear of several Stellites, steels and cemented carbides as a function of time for sliding under wet and dry conditions.A simple theoretical analysis of tool wear that applies to cutting green wood with cemented carbide tools is described. The analysis, which indicates the important parameters in the wear process, is used to predict the effect of carbide particle size on wear rate. Comparisons are made between the predicted and experimentally determined wear rates for two groups of cemented carbide materials. Good agreement is found between experimental measurements and theoretical predictions. It is shown that wear depends on carbide particle size. Superior wear resistance of cemented carbides is attributed to the high hardness and low chemical reactivity of the carbide phase. The improved wear resistance of the Stellites is attributed to the low reactivity of the matrix.     

纳米硬质合金刀具切削Al/SiC_p复合材料的实验

针对SiC颗粒硬度高,切削Al/SiCp复合材料时刀具磨损剧烈,本文提出用具有较高硬度、韧性及良好抗磨损能力的WC-7Co制备纳米硬质合金刀具,并对Al/SiCp复合材料进行了切削实验。研究了纳米硬质合金刀具磨损机理和Al/SiCp复合材料的切屑去除机理,以及刀尖处后刀面磨损值。研究认为,纳米硬质合金刀具磨损的机理为SiC颗粒的微切削作用引起的磨料磨损,及SiC颗粒对刀尖刃口的高频、断续冲击引起的微崩刃及微破损;Al/SiCp复合材料的切削实质是断续切削;去除机理为切屑的崩碎去除;纳米硬质合金后刀面磨损值较普通硬质合金小30%～50%。实验表明,纳米硬质合金较普通硬质合金更适于加工Al/SiCp复合材料。     

硬质合金刀具材料性能参数的灰色识别

采用灰色系统参数识别的方法，以材料的物理机械性能作为分析参数，对国产YT类和YG类硬质合金刀具材料与ISO标准牌号硬质合金之间的对应关系进行分析．结果与传统的依据材料成分的分类方法基本一致，为国际间参考使用硬质合金材料提供了理论依据。     

Effect of continuously grading fiber orientation face sheets on vibration of sandwich panels with FGM core

The main purpose of this paper is to investigate effect of continuously grading fiber orientation face sheets on free vibration of sandwich panels with functionally graded core using generalized power-law distribution. The benefit of using generalized power-law distribution is to illustrate and present useful results arising from symmetric, asymmetric and classic profiles. The fiber-reinforced composite material studied in the present work consists of silicon carbide fibers embedded in titanium matrix with the fiber volume fraction and fiber orientation graded in the radial direction. The face sheets have variation of the fiber orientation while the core has variation of fiber volume fraction. Generalized differential quadrature (GDQ) method is used to yield natural frequencies of the simply supported functionally graded sandwich (FGSW) panels on the basis of the 2-D, linear and small strain elasticity theory. The fast rate of convergence of the method is demonstrated and comparison studies are carried out to establish its very high accuracy and versatility. In this research work, a detailed parametric study is carried out to highlight the influences of continuously grading fiber orientation face sheets and different profile of fiber volume fraction and fiber orientation on the vibration characteristics of the FGSW panels.     

单涂层与复合涂层硬质合金刀具性能对比

随着涂层技术的进步，硬质合金刀具涂层种类也在不断地增加，从单一的化合物涂层朝着多元复杂化合物涂层发展。通过多次实验，将单涂层与复合涂层硬质合金的刀具寿命作了比较。研究结果表明，复合涂层刀具在提高切削性能方面效果是显著的。     

ELID超精密磨削钢结硬质合金及其表面质量分析

运用铁基结合剂金刚石砂轮与专用高频脉冲电源相配合,对钢结硬质合金（ＧＴ３５）进行在线电解修整（ＥＬＩＤ）精密磨削。分析了ＥＬＩＤ超精密镜面磨削异相非均质材料钢结硬质合金表面的磨削机理,并通过原子力显微镜对其表面进行了微观表面形貌的分析。