镍基熔覆涂层受冲击载荷作用下的性能研究

45钢及1Cr18Ni9Ti表面激光熔覆WFCL-11涂层，研究了激光熔覆涂层与基体界面及表面显微组织和硬度特点，分析在冲击载荷作用下，显微组织、结合性能、硬度变化等特点。发现了不同基材与熔覆材料对结合面性能的影响。     

激光熔覆Al65Cu2OCr15准晶态合金的相选择问题

研究了在45#钢基体表面激光熔覆Al65Cu20Cr15准晶态合金过程中，工艺参数激光功率（P）和扫描速度（v)对激光熔覆涂层相结构的影响。结果表明，激光功率和扫描速度的变化使基体材料对熔覆涂层的稀释率发生改变，随着激光熔覆稀释率的增加，熔覆层的相结构依次为λ＋I，I＋β，β，β＋d，d Fe，激光熔覆涂层相结构的差异使涂层具有不同的显微硬度，参数δ（P／v)决定激光熔覆过程的稀释度，从而直接影响激光熔覆准晶涂层的相结构，涂层的表面显微硬度也因涂层相结构的不同而有所差异。     

基于工业合金激光熔覆制备Fe基非晶涂层

以FeCoCrMoCBY块体合金为熔覆材料,采用激光熔覆在低碳钢表面制备非晶涂层,探讨不同激光功率对涂层成形及组织的影响,通过显微硬度仪、电化学工作站测试涂层显微硬度及耐腐蚀性能。研究结果表明,其他参数不变,激光功率为17.6~20.8 W时,涂层成形良好,与基材呈典型冶金结合。随激光功率增加,涂层稀释率升高,裂纹倾向增大,非晶化程度降低。激光功率为17.6 W时,涂层主要由非晶组成,稀释率低于24.2%,结构致密,包括热影响区、熔合区和熔覆区;涂层平均显微硬度为1 330HV,约高于基材9倍,在3.5%NaCl溶液中的耐腐蚀性能明显优于316L不锈钢。     

车用316L不锈钢上激光熔覆Co-9Al-12W合金组织及腐蚀性能分析

通过大功率半导体耦合激光器在车用316L不锈钢上激光熔覆Co-9Al-12W合金,通过硬度与稀释率确定了最优的激光熔覆工艺参数,实验测试分析钴基涂层的微观组织及腐蚀性能。研究结果表明:增大激光能量密度能提高基材熔融程度,达到更大的稀释率。能量密度120 J/mm~2熔覆合金形成的熔覆合金达到了最大的硬度59 6HV。位于基体和熔覆合金界面层区域形成了具有平面晶特征的金相组织,涂层和基材之间达到了冶金结合的状态。在钴基熔覆合金内存在γ-Co与Al_3W_2两种成分,Co与Fe主要出现在枝晶组织中。结果显示涂层和基材之间达到了冶金结合的程度,获得质量更优的熔覆合金。Al含量增大便会跟氧气发生相互作用得到Al_2O_3膜层,形成致密结构,达到钝化效果。     

铝合金表面激光熔覆铁基合金涂层过渡区的特征

为了在铝合金表面获得无裂纹的熔覆层并提高铝合金的表面强度,通过热喷涂预制涂层,结合激光重熔在铝合金基体上进行了激光熔覆试验.利用SEM,XRD和电子探针(EPMA)等对涂层的形貌和成分分布以及过渡区的相组成进行了研究.结果表明:在Al合金表面可以获得低稀释率、无裂纹的铁基熔覆层;在熔覆过程中熔覆层/基材结合面处,Fe和Al反应生成的短棒状FeAl金属间化合物镶嵌在铝合金基体中,避免了裂纹形成.反应过程中释放的反应热使得熔覆层/基材结合面处形成锯齿状形貌.     

激光熔覆制备Al65 Cu20 Cr15准晶态合金及其类似相的研究

研究了以45＃钢基体表面激光熔覆准晶态Al65Cu20Cr15粉末制备准晶及其类似相涂层过程中，激光功率和扫描速度对激光熔覆涂层相结构的影响。实验结果表明：由于激光切率和扫描速度的变化，基体材料对熔覆涂层的稀释程度发生改变；随着激光熔覆稀释率的增加，熔覆层的相结构依次为β＋i,β d,β,β Fe；激光熔覆粉末所制备的涂层结构致密，无孔隙和裂纹；涂层的表面显微硬度及摩擦系数等力学性能也因涂层相结构的不同而有所差异。     

42SiMn表面激光熔覆SiC纳米陶瓷涂层试验研究

采用激光熔覆工艺 ,在 4 2SiMn表面制备了纳米SiC陶瓷涂层 ,对涂层的成分、物相、微观组织等进行了分析。结果表明 ,选用合理的工艺参数 ,利用激光熔覆可以得到质量较好的纳米SiC陶瓷涂层 ,但SiC晶粒尺寸有所长大 ,且熔覆过程中有分解反应 ,产生纳米Si与C。     

16Mn钢基Ni合金激光熔覆层耐冲蚀性能研究

采用CO2连续波激光器在16Mn钢基材表面进行Ni基合金熔覆处理，采用XRD、SEM等分析了熔覆层的相组戍和微观结构，在不同的介质中研究了16Mn钢基和合金熔覆层的耐冲蚀性。研究结果表明，涂层主要由γ-Ni等组戍，枝晶组织细小均匀，涂层硬度比基体显著提高。在含有3％（质量分数）、SiO2磨粒的酸碱腐蚀溶液中，激光熔覆Ni合金涂层的16Mn钢基材的耐冲蚀性得到提高。     

激光熔覆生物陶瓷涂层生物相容性体内研究

将激光熔覆原位合成的钙磷涂层及TC4分别植入健康的Mongrel成年狗,术后15天、60天和180天观察涂层与基材、涂层与机体组织的结合形态及植入后对动物的组织影响.此外,用涂层材料进行肌肉植入实验,分别在15天、37天、60天和180天观察其组织生长形态.结果表明:激光熔覆原位合成的钙磷涂层在动物体内其表面有新骨产生,说明了涂层材料在机体内具有诱导骨生成的生物活性;观察动物的植入部位无感染,无组织吸收或增生等不良反应,材料与肌肉间未发现有不良反应,材料与肌肉界面覆盖的结缔组织层随种植时间延长而增厚.激光熔覆原位合成的钙磷涂层具有良好的体内生物相容性和活性,是一种体内生物陶瓷涂层材料.     

激光熔覆TiCp／Ni基合金复合涂层中TiCp的行为

通过激光熔覆TiCp/Ni基合金复合涂层微观组织的研究表明,TiC颗粒在熔覆过程中表面发生部分溶解,当凝固时,溶解的部分TiC在残留TiC颗粒上重新外延生长析出,并与基体合金元素产生附加合金化,同时,TiC颗粒成为从激光熔体凝固各相优先形核的基底;TiC颗粒与凝固前沿间的相互作用控制其微观分布。     

Strengthening soda-lime-silica glass by a low-expansion coating applied by melt dipping

A method of strengthening glass by application of a low-expansion glass coating is described. Soda-lime-silica glass rods were dipped vertically into a low-viscosity borate glass melt at 1140 to 1200 °C and rapidly withdrawn. Uniform well-bonded coatings, 100 to 200 m in thickness, were produced. The modulus of rupture (MOR) of unabraded rods coated with a 60 ZnO-40 B₂O₃ (wt%) glass (glass 1) was 548 M Pa, compared with 225 M Pa for a control set of uncoated rods; coated rods after abrasion gave 343 M Pa compared with 110 M Pa for abraded uncoated rods. Rods coated with glass 1 fractured uniformly into small pieces in a manner similar to thermally toughened glass. Approximate calculated axial stresses, using thermal expansion and other data, were 233 M Pa (compressive) in the coating (glass 1) and 56 M Pa (tensile) in the substrate rod. The magnitude of the calculated axial compressive stress in the coating was in good agreement with the increase in average strength of the rods after melt dipping. The results indicate that the fracture origin was probably at the outer coating/air surface and not at the substrate/coating interface, and that the flaw length was less than the coating thickness. Severe flaws on the original rod surfaces were probably filled during melt dipping, rendering them inoperative.     

Characterisation of bioactive glass coatings on titanium substrates produced using a CO2 laser

Titanium and its alloys are widely used in load-bearing bioinert implants. Bioactive glasses (BAGs) form a chemical bond with bone, but they are not suitable for load-bearing applications. Creating a BAG coating on a titanium implant could combine the best properties of both materials. The results tend to be poor when conventional firing methods are applied to coat titanium with BAG. A local application of heat to melt the glass can be achieved by a CO2 laser. A new method is introduced to create BAG coatings on titanium locally in a controlled manner, with a focused CO2 laser beam. The coatings produced by this method precipitate calcium phosphate in vitro. Processing parameters (number of coated layers, laser power, and processing atmosphere) providing a firm attachment of the glass and good in vitro bioactivity were identified. XRD analysis showed no crystallisation of the glass due to processing with the laser. EDXA indicated the formation of a calcium phosphate layer, which FTIR suggested to be a hydroxyapatite. The results show CO2 laser processing to be a promising technique for the manufacture of 30-40 microm BAG coatings on titanium.     

A scratch-resistant and hydrophobic broadband antireflective coating by sol-gel method

A double-layer broadband antireflective (AR) and scratch-resistant coating with hydrophobic surface is fabricated via sol-gel process using acid and base catalyzed silica as precursor solutions. The coating is composed of a dense and a porous silica films of which the refractive indices are high and low respectively, realizing a step-index gradient structure with glass as the substrate. The AR property of the coating is optimized to maximize the amplification yield of the laser disk amplifiers used in high power laser system. The average transmittance of BK7 glass coated in this way increased to more than 99.5% over the range of 500 to 850 nm. After NH₃-heat treatment at 200 °C, the scratch-resistance of the coating is improved in a large degree. Trimethylchlorosilane is employed to modify the coating surface to improve the optical stability by resisting moisture. These treatments can ensure that this broadband AR coating is durable for its real application.     

热喷涂激光预处理的应用与影响研究进展

综述了激光预处理技术在热喷涂中的应用研究进展,通过调整激光工艺对基体进行清理或刻蚀处理,能够完成对基体表面的净化与粗化,提升涂层服役性能。分析了激光预处理对涂层性能的影响,激光预处理后能增强涂层在基体表面的机械结合,改善涂层/基体界面润湿,降低孔隙率。明确了激光预处理在热喷涂中存在的问题,并展望了其应用前景与研究方向。      

Fabrication of titania-coated silica fibers and effect of substrate shape on coating growth rate

Titania coating was fabricated on fused silica glass fibers of 4-6 μm in diameter by the hydrolysis of Ti-tetraethoxide in ethanol at 20 °C. Changes in the coating thickness with the deposition time were examined by scanning electron microscopy and compared with those on flat soda-lime glass substrate examined by atomic force microscopy. Uniform titania coating was obtained, but severe cracking occurred on coatings thicker than 150 nm due to isotropic shrinkage during the drying process. The faster growth rate of coating on fiber than that on flat substrate could be explained by employing an ‘adhesion growth model.’ X-ray diffractometry showed that titania coating on fused silica glass plate was transformed to anatase-phase TiO₂ by annealing in air at 300 °C. This indicates that the titania coating on a fused silica glass substrate becomes crystalline after annealing at that temperature.     

超音速火焰喷涂硅酸盐玻璃涂层工艺研究

采用超音速火焰喷涂技术制备了硅酸盐玻璃涂层,通过扫描电镜、能谱、衍射和强度试验研究了涂层的组织特征、机械性能等.研究表明,制备玻璃涂层的最佳工艺为:粉末颗粒尺寸为25～50μm,氧气流量34～36m3/h,煤油流量13～14L/h,喷涂距离25cm;涂层组织较致密,玻璃涂层厚度可达到0.5mm以上;涂层基本呈非晶态,热喷涂后玻璃涂层冷却速度对涂层的析晶行为有一定影响;涂层与基体之间的结合形式为机械结合,涂层的内聚强度约为8MPa,其拉伸断裂形式为宏观脆性断裂,涂层具有一定硬度和抗冲击性能.     

Microstructural development in microsecond pulsed laser melted polycrystalline nickel

The microsecond Nd glass pulsed laser interaction with polycrystalline nickel was studied with particular emphasis on melting and the nature of the microstructural development following irradiation. The change in the melt pool shape and the melting efficiency as a function of the total laser power has been determined. Evidence is presented to show that for low energy pulse, the microstructural development accompanies fresh nucleation of grains and leads to a finer grain size than that of the substrate. At a higher energy level, growth competition leads to a coarser grain size. We also report a banded feature roughly parallel to the melt substrate interface that develops in the resolidified region during high energy interaction. These results are discussed in the light of our present understanding of rapid solidification processes.     

Copper Plating on SiCp by Cooling Crystallization and Its Effects on the Spreading and Infiltration of AlSi12 Alloy Melt

A new cooling crystallization method is applied to plate copper on SiCp. Cu(NO₃)₂·3H₂O is crystallized on SiCp by decreasing the solution temperature, and is heat-treated to obtain CuO coating which is finally reduced to copper coating. Based on the optimizing of SiCp content and CuO reduction temperature, the effects of copper plating on SiCp on the spreading and infiltration of AlSi12 alloy melt are studied. The results show that the optimum coating effect is achieved when the SiCp content is 11.63% and the reduction temperature of CuO is 475 °C. The spreading area of AlSi12 alloy melt on the 15 μm copper-coated SiCp increases by 53.27% compared to the uncoated SiCp when holds at 950 °C for 20 min, indicating that copper plating has a significant improvement on the wettability of AlSi12 melt and SiCp. Additionally, infiltration preparation of copper-plated SiCp/Al alloy composites is achieved at a pressure of 0.3 MPa, but not under pressureless conditions. The main reason for this is the granular Cu on SiCp cannot form a complete Cu film. Therefore, the formation of complete Cu films on SiCp is presumed to be an important development direction for solving the problem of infiltration preparing ultrathick SiCp/Al composites.     

Stretched polymer nanohairs by nanodrawing

A simple, yet innovative, method is presented for fabricating high-aspect-ratio polymer nanohairs (aspect ratio >20) on a solid substrate by sequential application of molding and drawing of a thin polymer film. The polymer film was prepared by spin coating on a rigid or flexible substrate, and the temperature was raised above the polymer's glass transition while in conformal contact with a poly(urethane acrylate) mold having nanocavities. Consequently, capillary forces induced deformation of the polymer melt into the void spaces of the mold and the filled nanostructure was further elongated upon removal of the mold due to tailored adhesive force at the mold/polymer interface. The optimum value of the work of adhesion at the mold/polymer interface ranged from 0.9 to 1.1 times that at the substrate/polymer interface.     

Laser surface modification of titanium substrate for pulsed laser deposition of highly adherent hydroxyapatite

Biomedical implant devices made out of titanium and its alloys are benefited by a modified surface or a bioactive coating to enhance bone bonding ability and to function effectively in vivo for the intended period of time. In this respect hydroxyapatite coating developed through pulsed laser deposition is a promising approach. Since the success of the bioactive ceramic coated implant depends mainly on the substrate-coating strength; an attempt has been made to produce micro patterned surface structure on titanium substrate for adherent hydroxyapatite coating. A pulsed Nd-YAG laser beam (355 nm) with 10 Hz repetition rate was used for surface treatment of titanium as well as hydroxyapatite deposition. The unfocussed laser beam was used to modify the substrate surface with 500–18,000 laser pulses while keeping the polished substrate in water. Hydroxyapatite deposition was done in a vacuum deposition chamber at 400°C with the focused laser beam under 1 × 10⁻³ mbar oxygen pressure. Deposits were analyzed to understand the physico-chemical, morphological and mechanical characteristics. The obtained substrate and coating surface morphology indicates that laser treatment method can provide controlled micro-topography. Scratch test analysis and microindentation hardness values of coating on laser treated substrate indicate higher mechanical adhesion with respect to coatings on untreated substrates.