Effect of nano-size nickel particles on wear resistance and high temperature oxidation resistance of ultrafine ceramic coating

1　INTRODUCTIONImprovementsinaerogasturbineengineandartilleryrecoilabsorberperformanceintermsofpower ,efficiencyandmassnecessitatetheuseofhighspecific strengthandlow densitymaterials,whichresultsinthedevelopmentofawiderangeoftitaniumalloysinthecompressorsectionof modern gasturbinesandartilleryrecoilabsorber .Titaniumalloys,ingeneral,easilyabsorboxygen ,leadingtooxidationandalphaphaseformationwhenexposedtohightemperature ( >5 0 0℃ )inair,whichlimitsthehightemperaturecapabilityofalloysdueto…     

Influence of Ta on microstructure and abrasive wear resistance of laser clad NiCrSiB coating

A mixture of NiCrSiB alloy powder and tantalum (Ta) powder was used as laser clad material to improve abrasive wear resistance of the Ni-based coating. The microstructure and wear resistance of the coating were investigated. Addition of Ta element works to suppress the growth of coarse M₇C₃ carbide in the coating, resulting in a decrease in aspect ratio of coarse carbide. In the abrasive wear test, in situ synthesized TaC particles well bond with Ni-based matrix, and are hardly pull out from wear surface. Grooves on the worn surface of NiCrSiB coating are much deeper and sharper than those in the NiCrSiB+Ta composite coating. Also, a weight loss of the composite coating is much lower than that of the NiCrSiB coating. The wear resistance of the laser clad Ni-based coating is enhanced to a much greater extent through the addition of Ta. This is attributed to the in situ synthesized hard TaC particles of nearly equiaxed shape, the Ni-based matrix strengthened by Ta and the decrease in aspect ratio of the coarse brittle carbides.     

钛合金材料防微动磨损涂层性能研究

采用超音速火焰喷涂工艺在TC4钛合金基体材料表面制备碳化铬系耐磨涂层,通过自制微动磨损试验设备测试不同对磨副、不同位移副值试验条件下带涂层的TC4钛合金材料的摩擦因数、磨损量等微动磨损性能,利用SEM、EDS、XRD等分析手段,对比分析微动磨损表面形貌、成分和相组成的差异.结果表明:不同摩擦副和位移副值条件下的摩擦因数...     

镍基纳米碳管/二氧化钛复合镀层的制备及性能

为了改善金属基材的表面性能,以钛铁矿为原料,利用微波等离子体化学气相沉积法制备了纳米碳管/二氧化钛复合粉体.采用复合电泳电沉积法在不锈钢基体表面制备了镍基纳米碳管/二氧化钛复合镀层;利用扫描电镜、X射线衍射仪、数显维氏硬度计和电化学测试等手段研究了纳米碳管/二氧化钛复合粉体对复合镀层结构和性能的影响.结果表明纳米碳管/二氧化钛复合粉体的加入有效地减小了复合镀层中镍的晶粒尺寸,促进了金属镍沿(111)晶面择优取向生长,改变了镍的电沉积层结构,提高了镀层的硬度,改善了镀层的耐腐蚀性能;在复合粉体的作用下,复合镀层的硬度与纯镍镀层相比提高了110%,腐蚀电位正移了23mV,腐蚀电流密度减少了0.991微安/平方厘米.     

激光重熔制备TA1表面Ni/Al复合抗高温氧化涂层

为了提高纯钛的高温抗氧化性能,采用电弧喷涂和等离子喷涂方法在纯钛表面制备Ni/Al复合涂层.利用激光重熔使得Ni层与Al层发生冶金反应,对试件进行800℃×40 h连续氧化.根据生成的金属间化合物特征研究纯钛的高温抗氧化行为.结果表明,经过表面改性处理后Ni/Al复合涂层可以显著提高纯钛的高温抗氧化性能.在激光重熔过程中Ni/Al复合涂层中的Al发生熔化扩散并与Ni形成以Ni_2Al_3相为主的扩散层.在氧化过程中Ni/Al复合涂层表面形成连续且致密的α-Al_2O_3氧化膜与大量NiAl相,表面扩散层中的富铝相可为表面提供充足的Al元素,进而对纯钛基体提供有效的高温抗氧化保护作用.     

镍基粉末高温合金的铣削加工

为了研究镍基粉末高温合金的切削加工性,用整体硬质合金TiC涂层和未涂层立铣刀对镍基粉末高温合金FGH95进行铣削试验.通过研究铣削力、铣削温度与铣削用量之间的关系,分析硬质合金刀具的磨损、破损机理,观察其切屑形态,得出了镍基粉末高温合金FGH95的铣削力和铣削温度经验公式.试验表明：硬质合金涂层刀具加工镍基粉末高温合金FGH95的性能要明显优于未涂层刀具,未涂层刀具的崩刃现象严重,涂层刀具最佳铣削速度为40m/min,铣削速度对铣削温度的影响最大,并且随着铣削速度的提高形成了锯齿状切屑.     

Electroless copper-phosphorus coatings with the addition of silicon carbide （SiC） particles

Cu-P-silicon carbide(SiC)composite coatings were deposited by means of electroless plating.The effects ofpH values,temperature,and different concentrations of sodium hypophosphite(NaH2PO2·H2O),nickel sulfate(NiSO4·6H2O),sodium citrate(C6H5Na3O7·2H2O)and SiC on the deposition rate and coating compositions were evaluated,and the bath formulation for Cu-P-SiC composite coatings was optimised.The coating compositions were determined using energy-dispersive X-ray analysis(EDX).The corresponding optimal operating parameters for depositing Cu-P-SiC are as follows:pH 9; temperature,90℃; NaH2PO2·H2O concentration,125 g/L; NiSO4·6H2O concentration,3.125 g/L; SiC concentration,5 g/L; and C6H5Na3O7·2H2O concentration,50 g/L.The surface morphology of the coatings analysed by scanning electron microscopy(SEM)shows that Cu particles are uniformly distributed.The hardness and wear resistance of Cu-P composite coatings are improved with the addition of SiC particles and increase with the increase of SiC content.     

Effect of Titanium Content on Microstructure and Wear Resistance of Hardfacing Alloy

The hardfacing alloys with different concentrations of titanium were deposited on carbon steel substrates by shielded metal arc welding, and the effect of titanium content on the microstructure characteristics of the hardfacing alloys was investigated. The wear resistance test of the hardfacing alloys was carried out by using a slurry rubber wheel abrasion test machine, and the wear behaviour was also studied. The results indicate that the addition of titanium can effectively promote the precipitation of the complex carbides of Nb and Ti due to the prior precipitation of titanium carbide which acts as nucleation sites for complex carbides. With the increase of titanium content, the wear resistance of the hardfacing alloys is increased gradually resulting from the refinement of microstructure and dispersive distribution of fine carbide precipitates. And the wear mechanism is mainly minimum plastic deformation with interrupted grooves due to the strengthening and protecting effects of carbide precipitates.     

Microstructure and mechanical properties of an in situ synthesized TiB and TiC reinforced titanium matrix composite coating

A titanium-based composite coating reinforced by in situ synthesized TiB and TiC particles was fabricated on Ti6Al4V by laser cladding. The microstructure and mechanical properties were investigated. The coating was mainly composed of β-Ti cellular dendrites and an eutectic in which a large number of rod/needle-shaped TiB and a few equiaxial TiC particles were homogeneously embedded. The microstructural evolution could be divided into four stages: precipitation and growth of primary β-Ti phase, formation of the binary eutectic β-Ti+TiB, formation of the ternary eutectic β-Ti+TiB+TiC, and solid transformation from β-Ti to β-Ti. Microhardness of the coating showed a gradient variation from the surface (about HV0.2 876) to the bottom (about HV0.2 660) and was prominently improved in comparison with that of the substrate. Fracture toughness of the coating also exhibited a gradient variation from the surface (6.3 MPa·m1/2) to the interface (11.9 MPa·m1/2). Wear resistance of the coating was significantly superior to that of Ti6Al4V.     

变质莱氏体钢中共晶碳化物的热处理粒化

研究了变质莱氏体钢中共晶碳化物的粒化过程 ,探讨了碳化物的粒化机理。结果表明 ,变质莱氏体钢的粒化过程为 :热处理温度T <1 1 0 0℃为碳化物均匀溶解阶段 ,T≥ 1 1 0 0℃为共晶碳化物在其晶格畸变能较大处溶断和随后由曲率半径决定的断网和粒化阶段。变质处理使共晶碳化物中产生的孪晶等晶格缺陷增多 ,降低了共晶碳化物的稳定性 ,加快了共晶碳化物的粒化动力学过程。     

Analysis on the Wear Performances of Cemented Carbide Tools Containing Ti in the Coatings When Machining Ti-6Al-4V Alloys

含钛涂层硬质合金刀具在加工Ti-6Al-4V合金时的磨损性能分析

孙剑飞1,2,3,杜大喜4,丁梓轩1,王凯1,白大山1,陈五一1,2

（1.北京航空航天大学 机械工程及其自动化学院,北京100191;

2.先进航空发动机协同创新中心,北京100191,中国;

3.北京市高效绿色数控加工工艺与装备工程技术研究中心,北京100191,中国;

4.北京航天石化技术装备工程有限公司,北京100166,中国）

摘要：由于钛元素的高亲和力,在加工钛合金时含钛涂层的硬质合金刀具似乎不是最佳的选择。然而在实践中,含钛涂层硬质合金刀具仍然广泛应用于钛合金的加工。为了系统的解释实践与理论之间的矛盾,进行了切削实验。使用俄歇电镜扫描切削区域来解析钛合金与硬质合金刀具之间的扩散过程。并通过分子热力学模拟Ti/Co扩散行为对这一过程进行仿真。实验和仿真结果表明,Ti/Co原子的相互扩散是导致扩散磨损的主要原因。溶解-扩散磨损是含钛涂层硬质合金刀具的主要磨损机制之一。此外,采用四种硬质合金刀具和另外两种金属陶瓷刀具以不同的速度切削Ti-6Al-4V合金,进一步验证含钛刀具在基体和图层中的高亲和力。实验结果表明,含钛硬质合金刀具一般不能用于钛合金的切削加工,但在合理的切削条件下,刀具与工件的亲和力较低。

关键词：磨损机理;Ti/Co扩散;分子热力学模拟;含钛硬质合金刀具;Ti-6Al-4V钛合金

     

TC4钛合金低磷化学镀工艺研究

针对TC4钛合金低磷化学镀,在浸锌活化和乳酸-乙酸络合条件下,对镍磷质量浓度比、温度、pH值、乙酸、乳酸等工艺因素对镀速和镀层磷含量的影响进行系列实验研究。用扫描电镜、能谱仪、显微硬度仪、X射线衍射仪对镀层的表面形貌、硬度和物相进行表征。研究结果表明：提高镍磷质量浓度比、温度、pH值,控制络合剂乳酸在20g/L～22g/L,乙酸在19g/L～20g/L范围内,均有利于低磷镀层的形成,平均镀速为25.6μm/h;镀层为晶态的Ni-P过饱和固溶体,平均粒径10μm,磷含量为2.56wt%,硬度为750.2HV.     

Fuzzy Pattern Recognition in Atlas and Images of the Unevenness of Carbide in Tool Steel

Fuzzy pattern recognition has been employed to identify some atlas and images of the unevenness of carbide in tool steel. Three models have been constructed. These models were based on fuzzy mathematics theory, as well as fuzzy pattern recognition method. Distribution rule of the unevenness of eutectic carbide in ledeburite steel is proposed in these models respectively.     

Confocal laser scanning microscope evaluation of early bacterial colonization on zirconium oxide and titanium surfaces: An in vivo study

To investigate the bacterial colonization on zirconium oxide and titanium surfaces in vivo quantitatively using a confocal laser scanning microscope (CLSM). Ten samples of zirconium oxide ceramic and commercially pure titanium were fabricated and polished using silicon carbide abrasive paper. One sample from each group was evaluated topographic pattern under a scanning electron microscope. One sample from each group was to evaluate roughness using a profilometer. Eight volunteers were selected. The samples were cemented at the buccal surfaces of upper first molars. All samples were removed after 48 hours, immersed in SYTO-9 and propidium iodide fluorescent to stain for adherent bacteria and observed with CLSM. Fewer bacteria were observed in zirconia group than titanium group. However, there was no statistical difference between two groups. The experimental results demonstrate that zirconium oxide may be considered as a promising material for dental implant abutments.     

镍基喷涂层抗焦粒冲蚀磨损性能的研究

在干熄焦余热锅炉中，焦位微尘对过热器管有冲蚀磨损作用，为提高过热器管的使用寿命，在１５ＣｒＭｏ过热器管表面热喷涂镍基合金．本文通过６７３～８７３Ｋ氧化试验和焦粒的室温冲蚀磨损试验，比较１５ＣｒＭｏ钢喷涂镍基合金前后的抗氧化能力和冲蚀磨损抗力。试验结果表明，镍基合金喷涂层的抗氧化能力和抗焦粒冲蚀磨损的性能均大大优于１５ＣｒＭｏ钢。     

原材料对原位合成强化相结晶状态的影响

钛合金表面耐磨性能差限制了电厂重要成品部件的寿命。采用激光熔覆方法,研究了不同原料状态和稀土添加对原位合成复合TiB/TiN钛基涂层强化相粒度以及分布均匀性的影响。采用X射线衍射分析(XRD)、扫描电子显微分析(SEM)和高分辨投射分析(TEM)技术等方法研究了强化相组织形貌,得出以下结论:分别采用h-BN和纯硼酸、尿素为原料形成的Core-shell结构为原料,涂层中均原位合成TiB/TiN强化颗粒,采用非晶态BN有利于获得细小强化相组织,但强化相含量相对较少;添加CeO2有利于强化相晶粒细化以及均匀分布。     

Experimental study on the free surface deformation in the oxide melt

1 Introduction The convective motion induced by local variations of surface tension along a liquid free surface is called Marangoni convection. Flows driven by a temperature gradient aligned parallel to the free surface are often named thermocapillary convection, which is often a dominating effect in material processing techniques. It is well known for the melt crystal growth that the thermocapillary convection becomes instable at high Marangoni numbers, which gives rise to temperature oscill…     

AI—5.6wt%Mn合金的激光表面重熔实验研究.

利用5kWCO2激光器对AI－5.6wt%Mn合金进行了一系列表面重熔实验，并对熔池的形貌和微观组织进行了分析研究。实验结果表明：重熔区组织较基体组织大大细化；随着生长速度的增大，重粉区组织由AI6Mn枝晶向α（AI） AI3Mn共晶、α（AI）胞／枝晶及完全无偏析固溶体转变，并对其形成原因进行了分析。熔池中存在的对流和激光扫描过程中工作台运动的不稳定造成了熔池表面波纹状组织和熔池中三维条带带状组织的出现。     

激光熔覆Cr3C2/Fe复合涂层的组织与磨损性能

采用5kWCO2连续激光器在低碳钢表面激光熔覆Fe基合金涂层（Fe55）及添加20%Cr3C（2质量分数）的Fe基合金复合涂层（Cr3C2/Fe）,研究了两种涂层的组织结构、显微硬度及耐滑动磨损性能。结果表明,Fe55涂层以亚共晶方式结晶,在初生柱状固溶体枝晶间存在大量的网状共晶组织。Cr3C2/Fe涂层中Cr3C2大部分溶解,原Fe55涂层中初生柱状固溶体枝晶产生等轴化,枝晶组织也明显细化。激光熔覆Fe55涂层主要由α-Fe和Cr23C6组成,Cr3C2/Fe涂层的主要组成相为γ-Fe;α-Fe,Cr23C6以及未熔Cr3C2。激光熔覆Cr3C2/Fe涂层的硬度和耐磨性明显优于Fe55涂层。