加工氧化锆陶瓷的金刚石涂层刀具的制备及切削试验研究

使用热丝化学气相沉积法(HFCVD)在硬质合金片以及球头铣刀表面沉积了微米金刚石薄膜(MCD),纳米金刚石薄膜(NCD)以及微米纳米复合金刚石薄膜(MNCD),通过扫描电子显微镜和拉曼光谱对其进行表征,结果呈现出典型的金刚石薄膜的性质,沉积质量高。金刚石薄膜与氧化锆陶瓷的摩擦磨损实验表明:金刚石薄膜能有效地降低对磨时的摩擦系数以及磨损率。使用三种金刚石薄膜涂层铣刀对氧化锆陶瓷进行铣削加工试验,结果显示:金刚石涂层刀具磨损率大幅度降低,刀具寿命显著增强。     

两步生长法制备大面积HFCVD金刚石薄膜

本文报道了一种利用两步热丝化学气相沉积法来提高金刚石薄膜质量的方法,在Si（100）基体上获得了面积45cm^2、厚度60μm的金刚石薄膜。第一步是在HFCVD反应室生长CVD金刚石薄膜,第二步是利用H2SO4：CrO3的饱和溶液对样品进行处理,再用H2O2：NH4OH（1：1）溶液冲洗干净,处理之后再沉积第二层金刚石薄膜。利用SEM、拉曼光谱、XPS分析金刚石薄膜。结果表明,薄膜厚度达60μm,纯度很高,并且在整个面积上是均匀的。     

热丝CVD金刚石涂层膜基界面结合强度研究新进展

硬质合金基体金刚石涂层工具产业化应用的主要障碍之一在于涂层的膜基界面结合强度较差,易引发涂层早期脱落。提高膜基界面结合强度、保证刀具正常使用寿命,已成为金刚石涂层工具产业化亟待解决的主要问题。我们介绍了近年来在提高硬质合金基体金刚石涂层膜基界面结合强度方面所取得的一系列研究新进展,并提出了进一步改善其膜基界面结合强度的新思路,以促进热丝CVD金刚石涂层工具的产业化应用。      

大孔径内孔表面金刚石薄膜涂层的制备

应用热丝化学气相沉积（HFCVD）工艺,并采用合适的衬底预处理方法和优化的工艺参数,在大孔径硬质合金内孔表面沉积了金刚石薄膜。分别采用SEM、EDS和喇曼光谱依次对衬底预处理前后内孔表面及沉积的金刚石薄膜进行了表征,并通过压痕实验评估了薄膜的附着强度。该压痕实验结果与薄膜的SEM及喇曼光谱表征的结果具有一致性。结果表明：采用合适的衬底预处理方法和优化的HFCVD工艺,可以在大孔径硬质合金内孔表面沉积高质量的金刚石薄膜。     

碳源浓度对CVD金刚石涂层质量的影响

在自制不锈钢钟罩式HFCVD设备上,以CH3COCH3和H2为气源,采用热丝CVD法在经过碱酸两步法预处理后的YG6硬质合金基体上制备了微米金刚石涂层;利用扫描电镜、Raman光谱仪、洛氏硬度计、维氏硬度计检测涂层的形貌结构、成分、附着性能和硬度,着重考察了碳源浓度对涂层质量的影响。结果表明过低碳源浓度造成涂层晶粒间存在缝隙,而过高的碳源浓度会使涂层晶粒细化,同时非金刚石相成分增加。以两步法工艺预处理基体,当碳源浓度为2%、沉积功率为4 kW、反应气压3 kPa、衬底温度为800℃、热丝基体距离为5 mm时,经4 h生长,可获得厚度为5.36μm、平均硬度HV为8 143.09、平均粒径1~2μm、纯度高、附着性能良好的微米金刚石涂层。     

CVD金刚石涂层刀具研究与应用前景

论述了CVD金刚石涂层硬质合金刀具的研究开发现状、存在的主要问题,重点介绍了硬质合金基体表面预处理方法及工艺。     

不同沉积功率对CVD金刚石涂层性能的影响

利用热丝化学气相沉积法(HFCVD),固定其他工艺参数,通过改变沉积功率在YG6硬质合金上制备金刚石涂层,并利用扫描电镜(SEM)、洛氏硬度计和Raman光谱对涂层进行性能测试。结果表明:两步法处理硬质合金基体,可以有效去除表层的Co,同时增大表面粗糙度,提高金刚石形核率,提高涂层附着力;涂层表面形貌观察可知,沉积功率4kW时,晶形完整,晶粒大小非常均匀致密,晶面主要呈现金刚石典型的(111)面生长;压痕测试表明,当功率为4kW时,涂层的结合力最好,表面均匀、平整;结合Raman光谱分析,功率4kW时,涂层质量很好。     

硬质合金成形铣刀的金刚石涂层热应力分析

针对B212型YG6硬质合金成形铣刀片,采用热丝化学气相沉积的方法,在其上沉积微米级金刚石薄膜。采用有限元分析的方法,研究成形铣刀片金刚石涂层的制备工艺,对热载荷作用下的金刚石薄膜和硬质合金基体间的热应力进行数值模拟计算,分析主要沉积工艺参数对金刚石涂层热应力的影响;采用扫描电镜、拉曼光谱及压痕实验等表征方法验证刀片不同部位金刚石薄膜的热应力特性。结果表明:较低的生长温度和较大的厚度有利于金刚石薄膜热应力的降低;在现有的制备条件下,保持沉积温度750℃基本恒定,沉积6 h后,薄膜厚度约为10μm,金刚石薄膜热应力较低,沉积质量较好,表现出良好的附着力,附着强度介于600 N和1000 N之间。     

沉积参数对硬质合金基体微/纳米金刚石薄膜生长的影响

基体温度、反应压力和碳源浓度等沉积参数决定热丝化学气相沉积金刚石薄膜的性能。运用正交试验方法,研究参数对硬质合金基体金刚石薄膜生长的综合作用。采用场发射扫描电镜（FE-SEM）、原子力显微镜（AFM）和拉曼（Raman）光谱检测薄膜的形貌结构、生长速率和成分。结果表明：随着基体温度的降低,金刚石形貌从锥形结构向团簇状结构转变;低反应压力有利于纳米金刚石薄膜的生成;生长速率受反应压力和碳源浓度综合作用的影响。     

柴油机增压器Si3N4陶瓷涡轮的制造与性能研究

利用热等静压法制备一种金属增韧的Si3N4陶瓷基增压器涡轮。这种新型涡轮既有常规氮化硅材料高强度、高导热系数和低膨胀系数等特性,又在很大程度上克服了陶瓷固有的脆性,增加了金属的可塑性,具有高韧性、高耐磨防腐蚀性能,可以在高强、高压等恶劣环境下工作。用Si3N4陶瓷代替现有K418镍基合金,提高了增压器的响应性,降低了柴油机的排放烟度,消除了涡轮出现的滞后响应。     

高强度多孔氮化硅陶瓷的制备及性能研究

以氮化硅为原料,以叔丁醇为溶剂,采用凝胶注模成型工艺和无压烧结工艺,制备出具有高强度和高气孔率的多孔氮化硅陶瓷。在浆料中初始固相含量固定为10vol%的基础上,研究烧结温度和保温时间对多孔氮化硅陶瓷材料的气孔率、孔径尺寸分布、物相组成及显微结构的影响,分析抗弯强度与结构之间的关系。结果表明,通过改变烧结温度和保温时间,可制备气孔率63.3%~68.1%的多孔氮化硅陶瓷;气孔尺寸呈单峰分布,平均孔径为0.97~1.42μm;抗弯强度随烧结温度提高或保温时间延长单调增大,在1750℃保温1.5h下达到最大值(74.2±8.8)MPa。     

TiZrNiCu钎焊Si3N4-MoSi2复合陶瓷与Nb接头组织与力学性能

采用高温活性钎料TiZrNiCu对Si₃N₄-MoSi₂复合陶瓷和金属Nb进行真空钎焊试验,研究了其典型界面组织组成及形成机理,分析了钎焊温度和保温时间对钎焊接头界面组织及力学性能的影响规律。结果表明,接头典型界面结构为Nb/β-Ti/(Ti. Zr)₂(Cu, Ni)+β-Ti+(Ti, Zr)₅Si₃/TiN+(Ti, Zr)₅Si₃+MoSi₂/Si₃N₄-MoSi₂。钎焊温度和保温时间主要通过控制Si₃N₄-MoSi₂复合陶瓷母材中Si原子向钎料中扩散程度,来影响钎缝中(Ti, Zr)₅Si₃化合物的数量及分布,进而影响钎焊接头的抗剪强度。在920 ℃/10 min的工艺参数下,Si₃N₄-MoSi₂/Nb接头的室温抗剪强度最高达到112 MPa,选择最优参数条件下的Nb/Si₃N₄-MoSi₂钎焊接头在500 ℃和600 ℃条件下进行高温剪切实验,其高温抗剪强度分别达到123 MPa和131 MPa。     

Grinding of Si3N4 Ceramic Balls with the Aid of Photo-Catalyst of TiO2

There are big needs from industry that the polishing process using loose abrasive be replaced by grinding process. This paper explores the possibility of replacement by investigating effects of the free radical reaction on the precision grinding performance. Free radicals were generated with the aid of TiO₂, a kind of photo-catalyst. Experiments were conducted on Si₃N₄ ceramic ball grinding with a metal bonded diamond wheel of SD8000 and SD16000. It is found that, for SD8000, the material removal rate increases by a factor of about 6 when adding 7.5 wt% of TiO₂ into grinding fluid. Ion exchanged water was used in this experiment. This increase in the material removal rate is expected to be due to the dressing effect of the free radicals of H and HO₂ in water, which are both very strong oxidizing agents. The free radicals of H and HO₂ are generated in the photocatalytic reaction process of TiO₂ with water and oxygen under ultraviolet rays. For SD16000 only adding 1 wt% of TiO₂ leads to a dramatic increase in material removal rate from 0.08 μm/hr to 0.55 μm/hr.     

Microstructure evolution of the Si3N4/Si3N4 joints brazed using Au-Ni-V filler alloys with different V content

Au-Ni-V filler alloys with different vanadium contents were designed to braze Si₃N₄ ceramic at 1373 K for 30 min, and the microstructures of brazing seams were investigated by SEM and TEM. When the Au-Ni-V filler alloy contains 5 at.% V, round-like Ni[Si, V, Au] precipitates form in the Au[Ni] solid solution matrix and a VN reaction layer with 0.5 μm thickness appears on Si₃N₄ interface. When the V content increases to 10 at.%, a new polygonal Ni₂SiV₃ phase occurs in the seam, and the Ni[Si, V, Au] precipitate coarsens and VN layer thickens. With increase of V contents to 15 and 20 at.%, laminar Ni[Au] and polygonal Ni₃V precipitates form. With 25 at.% V content in the filler alloy, the Ni₂SiV₃ and Ni₃V precipitates distribute homogenously in the brazing seam. These microstructure evolutions were attributed to the reaction between Si₃N₄ and vanadium, which forms VN reaction layer and releases Si into the molten alloy.     

Si3N4/Ti/Cu/Ti/Si3N4部分瞬间液相连接界面动力学

采用Ti(5μm)／Cu(70μm)／Ti中间层，通过改变连接时间和连接温度进行Si3N4。陶瓷的部分瞬间液相连接(PTLP连接)，用扫描电镜、电子探针对连接界面区域进行了分析，系统地研究了Si3N4／Ti／Cu／Ti／Si3N4 PTLP连接过程的动力学。结果表明，界面反应层的生长和等温凝固界面的迁移均符合扩散控制的抛物线方程。PTLP连接参数的优化不同于通常的活性钎焊和固相扩散连接的参数优化,反应层生长和液相区等温凝固这两个过程必须协调，才能同时提高室温和高温连接强度。     

Strengthening of transparent spinel/Si3N4 nanocomposites

In response to a need for improving the mechanical properties of optically transparent ceramics, the nanocomposites approach is used to strengthen transparent magnesium-aluminate spinel with Si₃N₄ nanodispersoids. The as-processed nanocomposites are found to be >70% transparent in the critical infrared wavelength range of 3-4.5 μm. Mie scattering combined with absorption by the Si₃N₄ nanodispersoids explains quantitatively the IR transmission behavior of these nanocomposites. The nanocomposites are also found to be transparent in the visible region. Upon heat treatment (1000 °C for 4 h in air), the optical properties of the nanocomposites remain unchanged. However, the heat treatment results in a 29% increase in the average strength, accompanied by almost doubling of the Weibull modulus, and an 85% increase in the indentation toughness. The improvements in mechanical properties after the heat treatment in these nanocomposites are explained qualitatively, based on generally accepted arguments involving surface-oxidation-induced surface compression and flaw-healing. While further work is needed to fully understand and exploit these effects, this first report on transparent nanocomposites could have broad implications for the creation of mechanically robust, transparent ceramics of the future.     

Deposition and characterization of CrN/Si3N4 and CrAlN/Si3N4 nanocomposite coatings prepared using reactive DC unbalanced magnetron sputtering

Nanocomposite coatings of CrN/Si₃N₄ and CrAlN/Si₃N₄ with varying silicon contents were synthesized using a reactive direct current (DC) unbalanced magnetron sputtering system. The Cr and CrAl targets were sputtered using a DC power supply and the Si target was sputtered using an asymmetric bipolar-pulsed DC power supply, in Ar + N₂ plasma. The coatings were approximately 1.5 μm thick and were characterized using X-ray diffraction (XRD), nanoindentation, X-ray photoelectron spectroscopy and atomic force microscopy. Both the CrN/Si₃N₄ and CrAlN/Si₃N₄ nanocomposite coatings exhibited cubic B1 NaCl structure in the XRD data, at low silicon contents (< 9 at.%). A maximum hardness and elastic modulus of 29 and 305 GPa, respectively were obtained from the nanoindentation data for CrN/Si₃N₄ nanocomposite coatings, at a silicon content of 7.5 at.%. (cf., 24 and 285 GPa, respectively for CrN). The hardness and elastic modulus decreased significantly with further increase in silicon content. CrAlN/Si₃N₄ nanocomposite coatings exhibited a hardness and elastic modulus of 32 and 305 GPa, respectively at a silicon content of 7.5 at.% (cf., 31 and 298 GPa, respectively for CrAlN). The thermal stability of the coatings was studied by heating the coatings in air for 30 min in the temperature range of 400-900 °C. The microstructural changes as a result of heating were studied using micro-Raman spectroscopy. The Raman data of the heat-treated coatings in air indicated that CrN/Si₃N₄ and CrAlN/Si₃N₄ nanocomposite coatings, with a silicon content of approximately 7.5 at.% were thermally stable up to 700 and 900 °C, respectively.     

Ti箔厚度对Si3N4/Ti/Cu/Ti/Si3N4部分瞬间液相连接界面结构及强度的影响

采用Ti／Cu／Ti中间层在l273K、180min的条件下，改变Ti箔厚度进行Si3N4陶瓷的部分瞬间液相(PTLP)连接，讨论Ti箔厚度对界面结构及连接接头强度的影响，用扫描电镜、电子探针对连接界面区域进行了分析。结果表明，在试验范围内，Ti箔厚度为10μm时Si3N4／Ti／Cu／Ti／Si3N4接头的室温强度最高，为210MPa。PTLP连接时，当连接温度和时间不变，且连接时间能保证等温凝固过程充分进行的条件下，Si3N4／Ti/Cu／Ti／Si3N4连接界面结构、反应层厚度、等温凝固层厚度随着Ti箔厚度改变而改变。