刀具基体表面织构化对硼掺杂金刚石薄膜性能的影响

目的分析硼掺杂织构金刚石薄膜的微观组织结构和表面质量,并探究刀具基体表面不同织构对薄膜结合强度和切削性能的影响。方法通过热丝化学气相沉积(HFCVD)法,分别在表面有椭圆织构、沟槽织构和无织构的硬质合金刀具上制备硼掺杂金刚石薄膜(BDD)。运用扫描电镜(SEM)观察各薄膜表面及横截面形貌;使用白光干涉表面三维轮廓仪观测各薄膜表面粗糙度;通过拉曼光谱仪检测各薄膜组织结构;通过铣削试验分析各薄膜刀具的切削性能。结果经测试,硼掺杂无织构金刚石薄膜(Boron doped un-textured diamond film,BDUTD film)的粗糙度为299.9 nm,硼掺杂椭圆织构金刚石薄膜(Boron doped elliptical texture diamond film,BDETD film)及硼掺杂沟槽织构金刚石薄膜(Boron doped groove texture diamond film,BDGTD film)的粗糙度分别为333、323.9nm,粗糙度略有增加。三种金刚石薄膜的厚度均为18μm,在相同切削条件下,经过铣削碳/碳-碳化硅(C/C-Si C)复合材料420 s后,BDUTD薄膜的剥落程度及其刀具磨损程度明显大于BDETD薄膜和BDGTD薄膜。结论硬质合金刀具基体表面织构化能够有效提高薄膜的结合强度,从而提高刀具的耐磨性。其中硼掺杂沟槽织构金刚石薄膜的切削性能相对更好,与普通硼掺杂金刚石薄膜刀具相比,硼掺杂织构金刚石薄膜刀具具有更长的使用寿命。     

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。     

PCB微钻不同金刚石涂层加工性能的研究

本文讨论了在微钻加工PCB板时化学气相沉积(CVD)金刚石薄膜的优化问题。首先进行了微米金刚石(MCD)薄膜、纳米金刚石(NCD)薄膜、硬质合金与PCB板的摩擦实验,通过观察磨损后的表面形貌及对磨损区域的化学元素分析,对比研究不同类型薄膜与PCB板的摩擦磨损特性;随后对MCD涂层、NCD涂层、类金刚石(DLC)薄膜涂层以及未涂层刀具进行了钻削PCB板的实验,研究不同类型薄膜微钻时的工作寿命与钻孔质量,综合比较微钻切削性能并优化薄膜类型。得到了以下结论:摩擦试验表明NCD-PCB摩擦对的摩擦系数最低(0.35),PCB板去除率最高;微钻实验的对比发现NCD涂层微钻的切削性能优异。在加工PCB板时,NCD薄膜最适应PCB板复杂的加工特性,是PCB微钻优良的硬质涂层。     

硬质合金微细刀具多种硬质涂层的研究

不同的刀具涂层具有不同的特性,为了寻找一种综合性能适用于微细刀具表面涂覆的涂层,本文在微细刀具基体材料硬质合金表面涂覆了包括微米金刚石(MCD)、纳米金刚石(NCD)、微纳米金刚石(MNCD)、普通类金刚石(DLC),含氢类金刚石(DLC-H)、四面体非晶碳类金刚石(TaC)薄膜及其复合薄膜在内的16种硬质薄膜。采用扫描电镜、三维白光干涉仪、洛氏硬度计、自制动载荷冲击试验机和摩擦磨损实验机分别表征了薄膜的微观表面和截面形貌、表面粗糙度、静和动载膜基结合强度及干摩擦学性能。实验发现,TaC薄膜虽在静和动载荷作用下,其膜基结合强度逊于DLC和DLC-H薄膜,但其表面光洁度,摩擦学性能明显优于DLC和DLC-H薄膜,可作为优秀的表面涂层。同时,将TaC薄膜与MNCD薄膜相结合,所得的MNCD+TaC薄膜兼具了底层MCD耐磨,中间NCD吸收冲击载荷,表层TaC薄膜光洁的优点,在所有薄膜中具有最低的摩擦系数和磨损率。     

织构对硼掺杂金刚石涂层刀具摩擦学性能的影响

利用激光技术在硬质合金刀具上分别制备椭圆织构和沟槽织构。同时,利用热丝化学气相沉积法(HFCVD)在刀具上分别制备硼掺杂无织构金刚石(Boron doped un-texture diamond film,BDUTD film)薄膜、硼掺杂椭圆织构金刚石(Boron doped elliptical textured diamond film,BDETD film)薄膜以及硼掺杂沟槽织构金刚石(Boron doped groove textured diamond film,BDGTD film)薄膜,通过摩擦磨损试验机,对不同织构形状的薄膜进行摩擦试验研究。另外,采用扫描电镜(SEM)、拉曼光谱(Raman)和能谱分析(EDX)对表面形貌、成分及残余物质进行分析。试验结果表明,BDUTD薄膜表现出最大平均摩擦因数,其值为0.13。BDETD以及BDGTD薄膜的平均摩擦因数分别为0.124和0.123。从磨损形貌来看,BDUTD薄膜及BDGTD薄膜对偶件的磨损直径分别为1.506 mm和1.254 mm。BDUTD薄膜的磨损表面黏附有少量团簇状的磨屑,且有破裂的金刚石晶粒出现。BDGTD薄膜的表面织构沟槽中有少量磨屑,金刚石晶粒几乎没有出现磨损。     

微米、纳米及微/纳米复合金刚石涂层的切削性能研究

利用化学气相沉积(chemical vapor deposition,CVD)法在硬质合金上制备纳米、微米以及微/纳米复合金刚石涂层,并进行了切削对比试验。通过测试已加工材料的表面粗糙度和金刚石涂层刀具前、后刀面磨损,对比分析了不同金刚石涂层的切削性能,同时总结了CVD金刚石涂层刀具的失效形式及机理。结果表明:纳米金刚石涂层刀具切削加工后的表面粗糙度值最小,Ra=0.942μm;微米金刚石涂层刀具切削加工表面粗糙度值最大,Ra=1.631μm;纳米涂层刀具的后刀面磨损最大,约为微米涂层的2倍,复合涂层的5倍;微/纳米复合金刚石涂层刀具膜/基结合力高,前、后刀面的金刚石涂层没有出现脱落,且刀具的磨损量较少;金刚石涂层刀具的主要失效形式是涂层的过早脱落,其失效主要是由金刚石涂层的残余应力大、涂层化学纯度低、内部产生微裂纹多,以及切削时表面粗糙度高、切削力大和刀具积屑瘤普遍等原因引起的。     

金刚石涂层刀具加工石墨的切削性能

为充分对比不同类型金刚石涂层刀具的切削性能,定制几种不同类型金刚石涂层刀具进行等静压石墨切削加工,并与WC硬质合金刀具和TiAlN涂层刀具的切削情况对比,分析不同类型金刚石涂层刀具的涂层形貌、切削寿命、加工后的表面质量以及切削力。结果表明:制备的金刚石涂层刀具的涂层形貌主要为纳米晶和微晶,其寿命是硬质合金和TiAlN涂层刀具的10倍以上,且几种不同类型的金刚石涂层刀具寿命差异较小;金刚石涂层表面的晶粒细化可以降低加工表面的粗糙度和切削力,涂层脱落是金刚石刀具的主要磨损形式。      

纳米/微米金刚石薄膜对钛合金摩擦性能和耐腐蚀性能的影响

金刚石薄膜可以加强牙科用钛合金(TC4)基台止动螺钉稳定性,延长其使用寿命。通过热丝辅助化学气相沉积(HFCVD)在TC4上沉积微米晶金刚石(MCD)和纳米金刚石(NCD)薄膜,分别采用SEM、AFM和Raman光谱对金刚石薄膜的形貌和质量进行表征,采用划痕实验检测了薄膜的结合强度。结果表明:沉积得到的NCD和MCD薄膜连续致密,表面粗糙度小,结合良好;金刚石薄膜有效地降低了TC4表面的摩擦因数和磨损率,NCD的摩擦因数约为0.09~0.15,MCD的约为0.18~0.22,其中在人工唾液环境下表现出更低的摩擦因数;金刚石薄膜人工唾液环境中能有效地提升材料的耐腐蚀性能,TC4表面沉积所得NCD薄膜的各项性能指标均优于MCD薄膜的。     

金刚石薄膜涂层刀具及其切削性能的实验研究

用燃焰法进行了金刚石薄膜涂层刀具的沉积实验,研究了刀具基体材料对金刚石薄膜形成的影响,通过对ＳｉＣ颗粒增强铝复合材料的切削实验,研究了以金属Ｗ为基体的金刚石薄膜涂层刀具的切削性能。     

CVD金刚石涂层刀具切削性能与磨损机理研究

针对普通刀具切削质量差、刀具耐用度低等问题，对CVD涂层刀具制备方法及切削性能进行研究。首先以硬质合金刀具为基体通过CVD方法制备金刚石涂层，分析涂层表面形貌。然后在不同条件下进行铝合金材料的干式切削试验，分析金刚石涂层对切削力、切削温度以及工件表面粗糙度的影响规律。最后，通过对刀具磨损机理的分析，讨论涂层对刀具使用寿命的影响。研究结果表明，所制备的涂层刀具能够降低切削力和切削温度，大大提高刀具的切削性能和工件的表面质量，并能有效提高刀具使用寿命。     

Cutting performance of multilayer diamond coated silicon nitride inserts in machining aluminum–silicon alloy

Aluminum–silicon (Al–Si) alloy is very difficult to machine and diamond tools are considered by far the best choice for the machining of these materials. Experimental results in the machining of the Al–Si alloy with diamond coated inserts are presented. Considering the fact that high adhesive strength and fine surface morphology play an importance role in the applications of chemical vapor deposition (CVD) diamond films, multilayer technique combining the hot filament CVD (HFCVD) method is proposed, by which multilayer diamond-coating on silicon nitride inserts is obtained, microcrystalline diamond (MCD)/ nanocrystalline diamond (NCD) film. Also, the conventional monolayer NCD and MCD coated inserts are produced for comparison. The as-deposited diamond films are characterized by field emission scanning electron microscopy (FE-SEM) and Raman spectrum. All the CVD diamond coated inserts and uncoated insert endure the aluminum-silicon alloy turning to estimate their cutting performances. Among all the tested inserts, the MCD/NCD coated insert exhibits the perfect behavior as tool wear due to its very low flank wear and no diamond peeling.     

Influence of textured diamond film on tribological properties of cemented carbide substrate

The texture of different shapes and spacing were machined on the carbide tool surface by laser technology, and the microcrystalline diamond film (MCD film) and nanocrystalline diamond film (NCD film) were deposited on the textured tools by hot filament chemical vapor deposition (HFCVD). The influence of different shape parameters and film types on tribological properties of the textured diamond coated tool was investigated using UMT-2 ball-on-disc friction tester. The surface morphology and wear scar morphology of the textured tool coated were characterized by scanning electron microscopy (SEM). The results showed that the friction coefficient of the narrow groove texture is less and more stable than those of the elliptical texture and the wide groove texture. The friction coefficient of the textured NCD film is generally less than that of the textured MCD film. Besides, for the same film, the more complex shape and the smaller spacing of the texture are, the stronger adhesion strength between the film and the substrate, and debris collection ability of the texture are, the less the friction and wear of the textured diamond film would be.     

Fabrication and application of nano/microcrystalline composite diamond coated drawing dies using alternative carbon sources

Nano/microcrystalline composite diamond films were deposited on the holes of WC-6%Co drawing dies by a two-step procedure using alternative carbon sources, i.e., methane for the microcrystalline diamond (MCD) layer and acetone for the nanocrystalline diamond (NCD) layer. Moreover, the monolayer methane-MCD and acetone-NCD coated drawing dies were fabricated as comparisons. The adhesion and wear rates of the diamond coated drawing dies were also tested by an inner hole polishing apparatus. Compared with mono-layer diamond coated drawing die, the composite diamond coated one exhibits better comprehensive performance, including higher adhesive strength and better wear resistance than the NCD one, and smoother surface (R_a=65.3 nm) than the MCD one (R_a=95.6 nm) after polishing at the same time. Compared with the NCD coated drawing die, the working lifetime of the composite diamond coated one is increased by nearly 20 times.     

Nanocrystalline CVD diamond coatings for drilling of WC-Co parts

Drilling of pre-sintered cemented carbide parts is a challenging task due to the high hardness and abrasive nature of the WC grains. This operation is commonly done using uncoated cemented carbide drill bits but the tool life is very limited requiring tool re-sharpening after a few holes. A solution for the improvement of the tool performance is here exploited by the use of nanocrystalline diamond (NCD) films as high abrasion resistant coatings. These coatings were grown in a hot filament chemical vapor deposition (HFCVD) reactor. Filament temperatures in the range of 1940-1980 °C were crucial to obtain highly adherent and very uniform coatings at the cutting edge and on the surfaces of the flutes. The performance of the coated tools was evaluated in through-hole drilling of a pre-sintered cemented carbide showing outstanding cutting efficiency when compared to that of an uncoated tool: maximal 940 mm/min infeed rates (app. 1 s to drill 17 mm) instead of 20 mm/min for the latter; absence of tool wear in contrast to a flank wear of about 50 μm in the uncoated tool after only 4 holes; hole edge integrity even at the highest infeed rates while grain decohesion at the hole edge takes place when using bare drill bits.     

CVD diamond coatings on geometrically complex cutting tools

The manufacturing of chemical vapour deposition (CVD) diamond coated shaft type cutting tools is demanding due to the complex design of the cutting edges and the cobalt content of the cemented carbide. The influencing parameters of substrate, pre-treatment and diamond film on the tool cutting performance are discussed. The optimised manufacturing route of CVD diamond coated thread milling drills is identified with the use of material and tribological tests. Following the optimised production of the tools, the thread milling drills are then applied in the machining of AlSi17Cu4Mg, whereby the tool performance is characterised with respect to their wear behaviour, the process forces and temperatures as well as the workpiece quality.     

Characterization of N-doped polycrystalline diamond films deposited on microgrinding tools

Chemical vapor deposited diamond films have many industrial applications but are assuming increasing importance in the area of microengineering, most notably in the development of diamond coated microgrinding tools. For these applications the control of structure and morphology is of critical importance. The crystallite size, orientation, surface roughness, and the degree of sp ³ character have a profound effect on the tribological properties of the films deposited. In this article, we present experimental results on the effects of nitrogen doping on the surface morphology, crystallite size, and wear of microgrinding tools. The sp ³ character optimizes at 200 ppm nitrogen, and above this value the surface becomes much smoother and crystal sizes decrease considerably. Fracture-induced wear of the diamond grain is the most important mechanism of material removal from a microgrinding tool during the grinding process. Fracture occurs as a consequence of tensile stresses induced into diamond grains by grinding forces to which they are subjected. The relationship between the wear of diamond coated grinding tools, component grinding forces, and induced stresses in the model diamond grains is described in detail. A significant correlation was found between the maximum value of tensile stress induced in the diamond grain and the appropriate wheel-wear parameter (grinding ratio). It was concluded that the magnitude of tensile stresses induced in the diamond grain by grinding forces at the rake face is the best indicator of tool wear during the grinding process.     

Nanocrystalline diamond coating tools for machining high-strength Al alloys

Diamond coating tools have been increasingly used for machining advanced materials. Recently, a microwave plasma-assisted chemical vapor deposition (CVD) technology was developed to produce diamond coatings which consist of nano-diamond crystals embedded into a hard amorphous diamond-like carbon matrix. In this study, the nanocrystalline diamond (NCD) coating tools were evaluated in machining high-strength aluminum (Al) alloy. The conventional CVD microcrystalline diamond coating (MCD) tools and PCD tools were also tested for performance comparisons. In addition, stress distributions in diamond coating tools, after deposition and during machining, were analyzed using a 2D finite element (FE) thermomechanical model.

The results show that catastrophic failures, reached in all except one machining conditions, limit the NCD tool life, which is primarily affected by the cutting speed. In addition, coating delamination in the worn NCD tools is clearly evident from scanning electron microscopy (SEM) and force monitoring in machining can capture the delamination incident. At a high feed, coating delamination may extend to the rake face. Furthermore, SEM observations of coating failure boundaries show intimate coating-substrate contact. Though the NCD tools are inferior to the PCD tools, they substantially outperform the MCD tools, which failed by premature delamination. The diamond coating tools can have high residual stresses from the deposition and stresses at the cutting edge are highly augmented. Further machining loading causes the stress reversal pattern which seems to correlate with the tool wear severity.     

Analyzing the performance of diamond-coated micro end mills

A method is presented to improve the tool life and cutting performance of 300 μm diameter tungsten carbide (WC) micro end mills by applying thin (<300 nm) fine-grained diamond (FGD) and nanocrystalline diamond (NCD) coatings using the hot-filament chemical vapor deposition (HF-CVD) process. The performance of the diamond-coated tools has been evaluated by comparing their performance in dry slot milling of 6061-T6 aluminum against uncoated WC micro end mills. Tool wear, coating integrity, and chip morphology were characterized using SEM and white light interferometry. The initial test results show a dramatic improvement in the tool integrity (i.e., corners not breaking off), a lower wear rate, no observable adhesion of aluminum to the diamond-coated tool, and a significant reduction in the cutting forces (>50%). Reduction of the cutting forces is attributed to the low friction and adhesion of the diamond coating. However, approximately 80% of the tools coated with the larger FGD coatings failed during testing due to delamination. Additional machining benefits were attained for the NCD films, which was obtained by using a higher nucleation density seeding process for diamond growth. This process allowed for thinner, smaller grained diamond coatings to be deposited on the micro end mills, and enabled continued operation of the tool even after the integrity of the diamond coating had been compromised. As opposed to the FGD-coated end mills, only 40% of the NCD-tools experienced delamination issues.