复杂形状钛管件内表面氧化铝涂层综合制备新工艺研究

摘要：为提高钛管件的耐腐蚀性能及抗冲刷磨损性能,研究了在具有复杂形状钛管件内表面制备氧化铝陶瓷涂层的新方法。先通过爆炸焊接制备了Ti／Al双金属复合管,再将其成形为复杂管件,接着通过微弧氧化将复合管件的铝层进行陶瓷化处理,从而将铝层部分转化为氧化铝层。采用XRD、SEM对氧化铝层的相组成及形貌进行了分析,并对氧化铝层与基体的结合强度、耐腐蚀性能和耐冲刷性能进行了表征。结果表明：涂层主要由γ-A12O3及α—A1203组成,其中γ-A12O3的厚度约为40／μm,α-A1203。的厚度约为10μm;陶瓷涂层与基体结合力达55N,涂层腐蚀电流比钛基体降低5个数量级。另外,氧化铝陶瓷涂层可以有效地防护基体被冲刷。     

沉积温度对类金刚石涂层表面形貌和性能的影响

采用直流等离子体增强化学气相沉积(DC-PECVD)技术,在不同温度下于YG8硬质合金基体上沉积了类金刚石(DLC)涂层,探讨了沉积温度对DLC涂层结构、表面形貌、厚度、显微硬度、耐磨损性能以及界面结合性能的影响。结果表明:随着沉积温度的升高,DLC涂层中sp3键的比例呈先增大后减小的趋势,并在160℃达到最大,为69%;沉积温度过高将导致DLC涂层出现石墨化;DLC涂层的厚度、显微硬度、耐磨损性能、界面结合力均随沉积温度的升高呈先增大后减小的趋势,当沉积温度为160℃时,涂层表面平整光滑、致密,此时涂层的厚度、显微硬度和界面结合力均达到最大,分别为3.2μm、2 395HV和63N;DLC涂层的显微硬度、抗磨损能力、厚度和界面结合强度随沉积温度的变化规律与sp3键含量密切相关。     

316L不锈钢表面氧化铝梯度涂层的制备

用热浸镀铝+高温热扩散工艺在316L不锈钢表面制备了铁铝梯度涂层,再用工业纯氮气中残留的氧气对其进行氧化处理制备了氧化铝梯度涂层;用OM、SEM、EDS、XRD、XPS和显微硬度仪等方法对涂层进行了分析。结果表明:750℃浸镀10 min的热浸镀铝涂层经950℃×4 h热扩散后,涂层表面质量较好,平均厚度120μm,与基体结合紧密;铝、铁呈良好梯度分布,表面最高硬度为800~850 HV;经900℃×4 h氧化处理后,氧与铝涂层进行了择优氧化,在距表面100nm以内原位反应生成了氧化铝,且除涂层表面是一层致密的氧化铝膜外,在膜以内氧化铝含量呈梯度分布。     

涂层材料热特性参数对点接触弹流润滑的影响

为探究涂层材料热特性参数对点接触弹流润滑的影响,选择3种不同方法制备的类金刚石（DLC）涂层和氧化锆陶瓷涂层,构建考虑涂层热特性的点接触弹流润滑模型,分析涂层材料、涂层厚度和润滑剂的流变性对接触区润滑性能的影响。结果表明：在弹流润滑状态下具有不同热特性的4种表面涂层导致了膜厚的差异,固体表面温度及润滑区温度场会随涂层热惯性变化;热惯性最小的DLC涂层加在快速运动表面能获得更高的膜厚;随着涂层厚度的增加,会引起固体表面的温度升高,使摩擦因数降低;非牛顿流体对压力、膜厚的影响很小,但与牛顿流体相比,能获得相对较低的温度。在弹流润滑状态下,涂层覆在快表面对于减小摩擦、提高膜厚是有益的。     

钛合金表面磁控溅射制备羟基磷灰石/氧化钇稳定氧化锆复合涂层

采用磁控溅射法在Ti6Al4V基体上制备了HA／YSZ复合涂层。用X射线衍射仪、扫描电镜、原子力显微镜和划痕法对涂层进行了表征。结果表明：用磁控溅射法可在Ti6Al4V基体上成功制备HA／YSZ复合涂层,涂层主要含有HA、ZrO2和Y2O3物相,此外还有少量的TCP和CaO相;涂层表面呈多孔状,有利于类骨组织的长入,表面显微粗糙度约为140nm,涂层厚度约为4μm;划痕法测量涂层与基体的附着力约为80N。     

热喷涂-激光制备CrFeAlTiC金属/玻璃陶瓷涂层

将铬铁粉、铁铝粉和钛粉按40%:40%:20%的比例混合,制成复合粉末,采用热喷涂-激光复合工艺在304不锈钢基材表面制备CrFeAlTiC金属/玻璃陶瓷涂层。借助光学显微镜、扫描电镜、能谱仪对涂层的宏观形貌、微观结构和组成成分进行了分析,并研究了其界面结合性能。结果表明:经激光处理得到的涂层厚度为20~30μm,表面较为平整、致密,且与基材呈良好的冶金结合;试样拉伸5%时,没有出现裂纹与涂层脱落的现象,涂层与304不锈钢基材界面结合性能较好。     

7050铝合金表面氧化膜厚度对其搅拌摩擦焊焊接接头性能的影响

采用阳极氧化法在7050铝合金表面制备了两种厚度的氧化铝薄膜,再用搅拌摩擦焊对铝合金进行焊接,研究了表面氧化膜厚度对焊接接头性能的影响。结果表明,氧化膜厚度对焊接接头性能的影响与焊接参数密切相关,当氧化膜厚度为12.μm,焊速为50 mm·min~(-1),搅拌针转速为600～800 r·min~(-1)时,接头的抗拉强度十分接近表面为自然状态接头的,而当氧化膜厚度为44μm时,接头焊缝氧化物含量增多,接头强度与自然状态接头的强度相比大幅降低;氧化膜提高了焊核区的硬度,膜厚度为44μm时焊核区硬度最高达265 HV,最低约180 HV。     

锌夹层添加对镁-铝异种金属搅拌摩擦点焊接头组织与性能的影响

对于镁-铝异种金属的搅拌摩擦点焊(Friction stir spot weld,FSSW),镁-铝界面处连续分布的脆性Mg-Al金属间化合物是影响其强度的关键因素。针对AZ31镁合金和2024铝合金薄板的FSSW,采用0.1 mm厚纯锌箔作为预置夹层,分析锌夹层添加对接头微观组织与力学性能的影响。结果表明,无夹层时,接头中仅在钩状区中的镁-铝界面处生成了厚度约为5μm的连续金属间化合物层,其余部分以机械结合为主,接头拉剪载荷仅为0.8 k N。锌夹层添加后,降低了钩状区中靠近匙孔一侧的过渡层厚度(约2μm),并使钩状区外侧界面处生成了新型Al-Zn、Zn-Mg化合物组织,起到了阻碍该区域Mg-Al金属间化合物生成的作用,达到了促进镁、铝之间冶金结合的效果。与无夹层相比,有夹层接头拉剪载荷提高了75%,达到1.4 k N。     

NAK80模具钢表面激光熔覆钴基合金涂层的组织和摩擦磨损性能

采用激光熔覆方法在NAK80模具钢表面制备钴基合金熔覆层,用扫描电镜、X射线衍射仪分析了熔覆层的显微组织,通过干滑动摩擦试验研究了熔覆层的摩擦磨损性能,分析了其磨损机制,并用三维表面形貌仪观察磨损试样的表面形貌。结果表明:熔覆层的主要组成相为Cr23C6、Co3Mo2Si、MoC、FeCr和γ-Co;熔覆层由涂层与基体界面处的平面晶区、涂层中部的胞状树枝晶区和表层的网状等轴晶粒区组成;经激光熔覆处理后的NAK80模具钢表面硬度和耐磨性得到了显著改善,与NAK80模具钢相比,熔覆层表面的平均摩擦因数降低了约34%,比磨损率下降了约91.3%;熔覆层的磨损机制为粘着磨损和轻微的显微切削。     

掺杂钨类金刚石膜的显微结构与性能

利用非平衡磁控溅射与离子源复合沉积技术,以高纯甲烷和氮气作反应气体,钨为溅射靶,在40Cr、Si(100)基片和不锈钢基体上分别制备了厚度约为2μm的掺杂钨类金刚石膜,并在类金刚石膜与基体间沉积了过渡层;应用X射线衍射、拉曼光谱、俄歇电子能谱等手段分析了掺杂钨类金刚石膜的显微结构和表面成分;应用球盘摩擦磨损试验机以及纳米硬度计等测试了膜的硬度、摩擦性能及结合强度。结果表明:所制备的膜表面均匀、致密、光滑,具有典型的类金刚石结构特征;掺杂的钨弥散分布在无定型的碳中,一部分形成W2C微晶相;当膜中钨原子分数约为20%时,膜的硬度最高,摩擦因数也相对较小,膜基结合力在70 N以上。     

Surface stresses in coated steel surfaces—influence of a bond layer on surface fracture

Thin hard coatings in the thickness range of only a few micrometers deposited by physical vapour deposition (PVD) on components or tools can improve the friction and wear properties by several orders of magnitude. A 2 μm thick TiN (E=300 GPa) coating on a high-speed steel substrate with a bond layer at the interface between the coating and the substrate was modelled by micro-level three-dimensional finite-element method (3D FEM) in order to optimise a coated surface with regard to coating fracture. Both compliant low modulus (E=100 GPa) and stiff high modulus (E=500 GPa) bond layers at the coating/substrate interface of 200 and 500 nm thickness were investigated. First principal stresses were simulated for scratch test geometry in the load range of 7.5-15 N. Very high stress concentrations of above 5700 MPa tensile stresses were observed in the bond layer just behind the contact zone for the stiffer bond layer. The stiff bond layer generated 5 times higher tensile stress maxima compared to the compliant bond layer. There was approximately 3.5 times larger strain in the compliant bond layer compared to the stiff bond layer. The general coating design advice based on this exercise is that when a bond layer is used e.g. for coating/substrate adhesion improvement should the bond layer be less stiff than the coating not to generate high and critical tensile stresses. The thickness of the bond layer may vary and is not critical with respect to generated stresses in the surface.     

钎焊单层金刚石砂轮的实验研究

单层高温钎焊超硬磨料砂轮具有传统砂轮和电镀砂轮无法比拟的优异磨削性能。利用高频感应钎焊的方法,以Ag-Cu合金和Cr粉为钎料,在一定的钎焊工艺条件下进行了实验研究,实现了金刚石与钢基体间的牢固化学冶金结合。扫描电镜分析发现在Ag-Cu-Cr与金刚石的界面之间形成CrC,与钢基体结合界面之间形成(FexCry)C,这是实现合金层与金刚石及钢基体之间都有较高结合强度的主要因素,并在相同的磨削参数条件下与电镀砂轮进行了对比实验,取得了较好的结果。     

Combined influences of mechanical properties and surface roughness on the tribological properties of amorphous carbon coatings

Carbon films (∼2 μm thick) with a range of mechanical properties and underlying substrate roughnesses were evaluated for delamination and wear under conditions of combined impact and sliding contact. One-side-coated and both-sides-coated titanium alloy pin and disk wear couples were assessed using a custom-made impact/sliding pin-on-disk apparatus in a colloid-based blood volume expansion medium. The normal stress distribution along the film/substrate interface upon impact loading by a smooth titanium alloy pin was modelled analytically for each coated system. For disk surface roughness centre-line average (R_a) values below 0.05 μm, the area of disk film delamination was shown to correlate with the presence of tensile stress at the film/substrate interface. The interfacial tensile stress was shown to occur when there was a film/substrate elastic modulus mismatch, either within or outside the perimeter of contact, depending on the direction of the film modulus deviation. We propose that the tensile stress promotes delamination by lifting the film locally from the substrate. With increased disk R_a, the area of disk coating loss tended to decrease, because the surface roughness improved the mechanical bonding of the composite system.     

304不锈钢表面预处理对沉积CrMoN涂层性能的影响

使用砂纸将对304不锈钢基体依次打磨至1200^#(1^#工艺)、2000^#(2^#工艺),以及打磨磨至2000^#并经粒度0.5μm金刚石抛光膏抛光(3^#工艺)后,在其表面沉积CrMoN涂层,研究了涂层的物相组成、表面与截面形貌、硬度、表面疏水性、耐腐蚀性能和导电性。结果表明:1^#工艺预处理基体表面沉积涂层的表面粗糙度最大,2^#工艺预处理后的次之,3^#工艺预处理后的最小;涂层均由CrN,Cr₂N,Mo₂N等物相组成;随着基体表面粗糙度的降低,涂层的显微硬度、自腐蚀电位和水接触角增大,自腐蚀电流密度、极化后的界面接触电阻降低;2^#工艺预处理基体表面沉积CrMoN涂层的综合性能优异,与3^#工艺预处理的接近。     

用表面活化技术提高金刚石与镀层的结合性能

分别用活化处理和未活化处理的金刚石磨粒制备了电镀金刚石工具,通过扫描电子显微镜观察金刚石与镀层的结合状况。对氧化铝陶瓷材料进行钻削加工,对比电镀金刚石钻头在耐用度期间的陶瓷材料去除体积。结果表明,经活化处理的金刚石表面沉积分散的钯质点,工具电镀过程中,在金刚石与镀层间的结合面上形成分散的连接点。应用表面活化技术制作电镀金刚石工具,可使金刚石与镀层形成牢固连接,改善镀层与金刚石的结合性能,其氧化铝陶瓷材料去除体积是未经活化处理金刚石电镀钻头的1.5倍,明显提高了电镀金刚石工具的磨削性能和使用寿命。     

Ni-Cr合金真空感应钎焊单层金刚石砂轮的实验研究

利用真空感应钎焊方法 ,用Ni Cr合金片作钎料 ,实现了金刚石与钢基体间的牢固连接。利用扫描电镜和X射线能谱 ,结合X射线衍射结构分析 ,发现Ni Cr合金中的Cr原子与金刚石表面的碳原子反应生成稳定连续的CrC膜 ,在与钢基体结合界面上生成 (FexCry)C ,这是实现合金层与金刚石及钢基体之间都有较高结合强度的主要因素。最后通过磨削实验验证了金刚石确有较高把持强度。     

CVD金刚石厚膜刀具切削性能的试验研究

分析了CVD金刚石厚膜刀具材料的性能特点 ,对CVD金刚石厚膜车刀进行了精密切削和难加工复合材料切削试验 ,结果表明 :CVD金刚石厚膜刀具加工铝合金的表面粗糙度可达Ra0 0 5 μm ;切削难加工复合材料时刀具耐磨性和使用寿命明显优于硬质合金刀具、PCBN刀具和PCD刀具     

Numerical analysis of Nd:YAG pulsed laser polishing CVD self-standing diamond film

Chemical vapor deposited(CVD) diamond film has broad application foreground in high-tech fields.But polycrystalline CVD self-standing diamond thick film has rough surface and non-uniform thickness that adversely affect its extensive applications.Laser polishing is a useful method to smooth self-standing diamond film.At present,attentions have been focused on experimental research on laser polishing,but the revealing of theoretical model and the forecast of polishing process are vacant.The paper presents a finite element model to simulate and analyze the mechanism of laser polishing diamond based on laser thermal conduction theory.The experimental investigation is also carried out on Nd:YAG pulsed laser smoothing diamond thick film.The simulation results have good accordance with the results of experimental results.The temperature and thermal stress fields are investigated at different incidence angles and parameters of Nd:YAG pulsed laser.The pyramidal-like roughness of diamond thick film leads to the non-homogeneous temperature fields.The temperature at the peak of diamond film is much higher than that in the valley,which leads to the smoothing of diamond thick film.The effect of laser parameters on the surface roughness and thickness of graphite transition layer is also carried out.The results show that high power density laser makes the diamond surface rapid heating,evaporation and sublimation after its graphitization.It is also found that the good polish quality of diamond thick film can be obtained by a combination of large incident angle,moderate laser pulsed energy,large repetition rate and moderate laser pulse width.The results obtained here provide the theoretical basis for laser polishing diamond film with high efficiency and high quality.     

金刚石表面的膜层沉积处理及其感应钎焊的研究

将热丝化学气相沉积(HFCVD)处理的金刚石作为磨料感应钎焊制作金刚石工具。HFCVD处理试验中,混合气为H2和CH4(体积流量比为100∶1.5),炉内压力为2.0kPa,700℃下处理45min后,在金刚石表面沉积了一层非晶碳膜。感应钎焊HFCVD处理的金刚石显示,出露部分的金刚石棱边能保持良好的锋利性;浸没在钎料层下面的金刚石表面形成了有均匀孔隙且形状不规则的铬碳化合物,液态钎料充填这些化合物孔隙之间,能够增强钎料对金刚石的把持强度。3种金刚石磨料感应钎焊制作的金刚石磨盘的高效重负荷石材磨削试验显示,HFCVD处理的金刚石的整体破碎率和脱落率最低。     

硫化锌基底上减反膜的镀制

硫化锌是红外波段重要的光学材料 ,在许多光电系统应用中 ,要求镀制适当的减反膜增加其透过率。介绍了硫化锌基底上的减反膜 ,该设计是用薄的氧化钇层作为与硫化锌的结合层 ,用一氧化硅和锗分别作为低、高折射率膜料的膜堆组成的。这种五层膜满足环境稳定性标准 ,在 3μm～ 5 μm波段的某应用范围内平均透过率即可达 96% ,并在 4.2 μm处有超过 98%的峰值透过率。