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.     

激光熔覆Ni+Cr2O3复合涂层的耐蚀性

研究了激光搭接熔覆Ni+Cr2 O3复合涂层在 0 .5mol/LH2 SO4 +0 .5mol/LNaCl水溶液中的电化学行为 .试验表明Cr2 O3粒子在激光熔池中发生了完全溶解 ,涂层具有胞状枝晶组织特征 .激光熔覆Ni+Cr2 O3复合涂层比单一熔覆Ni合金涂层和 2Cr13马氏体不锈钢基材具有更低的维钝电流密度和更宽的钝化区范围 ,明显改善了在该腐蚀介质中的抗点蚀能力 .     

Microstructure and electrochemical behavior of laser cladded HA coating on pure titanium TA2

Hydroxyapatite (HA, Ca10(PO4)6(OH)2) coating was fabricated on pure Ti (TA2) by laser cladding technology. The phase structure, microstructure, microhardness and electrochemical behavior of the laser cladded HA coating in artificial body fluid were investigated. The results show that the HA coating is mainly composed of highly crystallized HA. A transitional layer between HA coating and Ti substrate is formed. Microhardness measurement shows the gradually increasing of microhardness from 150 HV at TA2 substrate to 600 HV at transitional layer, and followed by a decreasing to 400 HV at HA coated layer. Electrochemical corrosion tests show that the HA coating has higher open circuit potential , lower corrosion current density and corrosion rate in comparison to the TA2 substrate.     

包覆法制备Gp/SiC复合材料的显微结构和性能

以不同粒径的石墨颗粒和SiC粉体为原料,采用SiC粉体包覆石墨颗粒的方法,于2000℃热压制备了石墨/碳化硅（Gp/SiC）复合材料.利用扫描电子显微镜（SEM,EDS）分析了材料的金相和断口显微结构.研究表明,石墨粒径较小且质量分数较少的复合材料比石墨粒径较大且质量分数较多的复合材料在热压工艺中更致密.石墨颗粒呈岛状紧密地镶嵌在SiC基体中,石墨与SiC界面处C和Si的扩散不明显.复合材料的相对密度、抗折强度,断裂韧性和硬度随石墨粒径和质量分数的减少而增加.断口形貌表明SiC陶瓷基体为脆性,石墨为韧性断裂.当石墨粒径为125μm、SiC与石墨的质量比为3.5时,复合材料的综合性能最佳,开口气孔率为0.3%,相对密度为97.9%,抗折强度为75±15 MPa,断裂韧性为5.4±0.5 MPa.m1/2,硬度为26.8±3GPa.     

2738模具钢表面激光熔覆Ni基WC复合涂层的摩擦磨损性能

在2738模具钢表面通过CO2激光熔覆制备Ni基WC复合涂层。分别对2738钢基体和Ni-WC激光熔覆层进行干摩擦试验。用三维表面形貌仪测量磨损体积,用扫描电镜观察磨痕的表面形貌。试验结果表明,Ni-WC复合涂层试样的硬度显著提高,表面硬度超过1200HV,保证了Ni-WC熔覆层的耐磨性。熔覆层的平均摩擦因数约为0.24,与2738钢基体的摩擦因数0.43相比,降低了约44%。熔覆试样的比磨损率比基体试样的比磨损率下降了96.7%,WC硬质相提高了摩擦副表面的承载能力。磨粒磨损为Ni-WC复合涂层的主要磨损机理。     

钛合金表面激光熔覆Cr3C2/Ni基合金复合涂层的微观组织

将质量分数为25％的Cr3C2／Ni基合金混合粉末预置在TCA合金表面，利用5kW横流CO2激光器进行激光熔覆试验，得到Ni基Cr3C2复合涂层．利用SEM和XRD对熔覆层的微观组织和相组成进行了分析，采用HXD—1000T数字式显微硬度计测量了熔覆层的硬度．结果表明，Ni＋Cr3C2复合涂层存在γ-Ni、TiC、CrTC扑M23（C，B）6和CrB等相，熔覆层硬度在600～900HV之间．     

SiB6-MoSi2复合涂层显微结构及抗氧化性能的研究

采用脉冲电弧放电法在SiC-C/C复合材料表面制备硼化硅和硅化钼的复相(SiB6-MoSi2)抗氧化涂层.借助X射线衍射、扫描电子显微镜对复合涂层的晶相组成、显微结构和抗氧化性能进行了表征与测试.研究了不同晶相组成(m[MoSi2]/m[SiB6]=Cp)对SiB6-MoSi2涂层显微结构的影响.结果表明:当晶相组成m[MoSi2]/m[SiB6]=1∶4时,制备的涂层致密均匀,在1 773K氧化156h后失重仅为2.12%,复合涂层氧化失效是由于长时间氧化后涂层挥发变薄,不能及时有效的愈合气相(CO和CO2)的逸出产生的氧化孔洞等缺陷导致的.     

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.     

Microstructure and performance of laser cladding TiB2 and Nickel-coated graphite composite coating on stainless steel 9Cr18

Stainlesssteel9Cr18withhighhardnessandanti wearpropertyiswidelyusedinthefieldsofbothna tionaldefenseandciviluse,especiallyapplicationintheaero enginebearingsandnationaldefenseaccoutre ments.Thetechnologyoflasercladdinghighhardness,antiwearandantifrictionc…     

工具钢表面激光熔覆Co基合金涂层的组织及性能

通过送粉式激光熔覆在碳素工具钢(T10钢)表面制备了Co基合金熔覆涂层。利用扫描电子显微镜(SEM)和X射线衍射仪(XRD)分析其微观结构和相组成。结果表明:熔覆层中主要有γ-Co相以及其他相,包括Cr23C6、Co7W6和CrNi。从熔池与基体界面到熔覆层表面存在不同的凝固形态,依次为平面晶(在界面处)、胞状晶和树枝晶。微观组织较细的树枝晶强化了熔覆层,因而激光熔覆层的显微硬度增加,耐腐蚀性提高。     

Dry wear behaviors of wear resistant composite coatings produced by laser cladding

Using different proportional mixtures of Ni-coated MoS2, TiC and pure Ni powders, new typical wear resistant and selflubricant coatings were formed on low carbon steel by laser cladding process. The microstructures and phase composition of the composite coatings were studied by SEM and XRD. The typical microstructure of the composite coating is composed of multisulfide phases including binary element sulfide and ternary element sulfide, γ-Ni, TiC and Mo2C. Wear tests were carried out using an FALEX-6 type pin-on-disc machine. The friction coefficient and mass loss of three kinds of MoS2/TiC/Ni laser clad coatings are lower than those of quenched 45 steel, and the worn surfaces of the laser cladding coatings are very smooth. Because of high hardness combined with low friction, the laser cladding composite coating with a mixture of 70% Ni-coated MoS2, 20%TiC and 10% pure Ni powder presents better wear behaviors than the composite coating with other powder blends. The composition analysis of the worn surface of GCr15 bearing steel shows that the transferred film from the laser cladding coating to the opposite surface of GCr15 bearing steel contains an amount of sulfide, which can change the micro-friction mechanism and lead to a reduced friction coefficient.     

Microstructure and wear resistance of in situ NbC particles reinforced Ni-based alloy composite coating by laser cladding

The in situ synthesized NbC particles reinforced Ni-based alloy composite coating was produced by laser cladding a precursor mixture of Ni-based alloy powder,graphite and niobium powders on a steel substrate.The microstructure,phase composition and wear property of the composite coating were investigated by means of scanning electron microscopy(SEM),X-ray diffraction(XRD)and dry sliding wear test.The experiment results show that the composite coating is homogeneous and free from cracks,and about 0.8 mm thick.The microstructure of the composite coating is mainly composed of NbC particles,CrB type chromium borides,γ-Ni primary dendrites,and interdendritic eutectics.CrB phases often nucleate and grow on the surface of NbC particles or in their close vicinity.NbC particles are formed via in situ reaction between niobium and graphite in the molten pool during the laser cladding process and they are commonly precipitated in three kinds of morphologies,such as quadrangle,cluster,and flower-like shape.Compared with the pure Ni-based alloy coating,the microhardness of the composite coating is increased about 38%,giving a high average hardness of HV0.21000,and the wear rate of the composite coating is decreased by about 32%,respectively.These are attributed to the presence of in situ synthesized NbC particles and their well distribution in the coating.     

送粉激光熔敷耐磨涂层制备工艺与组织结构

采用20%WC作为镍基自熔合金的掺杂增强相，研究了该复合材料在送粉激光熔敷工艺条件下的熔敷层显微组织、显微硬度与熔敷工艺规范间关系，得出了在实验条件下的优化工艺参数：激光功率为2．5kW(光斑离焦量60mm)；扫描速度为2．4mm／s；送粉量为3．0g／min．     

Microstructure of aluminum/copper clad composite fabricated by casting-cold extrusion forming

An aluminum/copper clad composite was fabricated by the casting-cold extrusion forming technology and the microstructures of the products were observed and analyzed.It is found that aluminum grains at the interface are refined in the radial profiles of cone-shaped deformation zone,but the grains in the center maintain the original state and the grain size is non-uniform.A clear boundary presents between the refined area and center area.In contrast,the copper grains in the radial profiles have been significa...     

Ti-based composite coatings with gradient TiC x reinforcements on TC4 titanium alloy prepared by laser cladding

TiC _x -NiTi₂/Ti cermet composite coatings C1 and C2 with gradient TiC _x reinforcements were prepared on TC4 titanium alloy by laser cladding method. The microstructure and phase compositions were analyzed by means of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) meter. The TiC _x exhibited a dendritic microstructure, and homogeneously dispersed in the Ti-based matrix where NiTi₂ was embedded. With increasing ingredient supercooling, temperature gradient and cooling temperature, the dendrites displayed a finer morphology with longer primary trunks and intensified side branches in the dilution zone. But the smoothed, coarse columnar ones became dominant in the upper clad layer due to the repeated energy input during multi-track cladding. The Vickers microhardness presented a linear change trend through the cross-sections, which well confirmed the gradient distribution of TiC _x . With more TiC _x , C1 presented higher hardness than C2.     

Gr/Al-0.7Si-1.2Mg复合材料制备及摩擦性能研究

采用二次热压法制备Gr质量分数为10%~25%的Gr/Al-0.7Si-1.2Mg复合材料,研究了制备工艺对组织结构及其摩擦磨损性能的影响.结果表明,采用较快速率升温的热压法可有效防止石墨铝复合材料制备过程的有害界面反应,得到组织均匀且致密的石墨铝基复合材料.Gr/Al-0.7Si-1.2Mg复合材料的摩擦系数随载荷的增大而降低,在较大载荷时,可形成完整的石墨润滑膜,不同石墨含量的复合材料的磨擦系数趋于一致,达到0.17.石墨含量高的复合材料容易形成润滑层,所以摩擦系数在较低载荷下就能达到最小值.复合材料相对密度对磨损率的影响较大,接近理论密度的复合材料在本研究试验条件下能保持较低的磨损率,最低可达到0.5×10-3~2.1×10-3mm3/m.     

Morphology and tribological properties of Ni/n-SiO_2 composite coatings by pulse-reverse current brush-plating

1INTRODUCTION Pulse reversecurrent(RC)platingisanew technologycomingwithpulsecurrent(PC)andre versecurrent.Onthisaspect,earlierstudiesmani festedthat[16],intheconditionofRC,theeffectofelectricdoublelayerwasrestrained,thecontrol ofcrystallinegrowthwasenfor…     

Microstructure and corrosion properties of laser cladding MoNi based alloy coatings

Mo-based alloys are widely used for their excellent wear and corrosion resistance as well as high temperature resistance.Mo-NiCrBSi and Mo-Ni alloy coatings were prepared on 1020 water wall tube by laser cladding technology in the present study.The microstructure and phase compositions were analyzed by means of the scanning electron microscopy(SEM),energy-dispersive spectroscopy(EDS)and X-ray diffractometry(XRD).The corrosion properties of the coatings were evaluated by an electrochemical experiment at room temperature in 3.5 wt.%NaCl electrolyte.With increasing content of Mo,the structure homogeneity in Mo-Ni coatings deteriorated,the grain size increased,the average hardness and the corrosion resistance declined,due to the more content of harmful phases.Compared to the Mo-Ni coatings,the overall performance was better for the Mo-NiCrBSi,which had the higher hardness contributed by the element B and Si as well as the better corrosion resistance due to the addition of Cr.     

激光熔覆Al2O3陶瓷涂层组织结构

研究了45钢表面激光熔覆等离子Al2O3陶瓷喷涂层的组织结构、硬度及滑动磨损特性。结果表明,等离子喷涂Al2O3陶瓷涂层呈层片状,涂层疏松,由α－Al2O3,ZrO2和γ－Al2O3组成。激光熔覆Al2O3陶瓷涂层致密,由α－Al2O3及ZrO2组成。激光熔覆Al2O3涂层硬度较高,滑动磨损时其耐磨性也明显优于等离子喷涂Al2O3陶瓷涂层。     

Preparation and properties of the Ni-Al/Fe-Al intermetallics composite coating produced by plasma cladding

A novel approach to produce an intermetallic composite coating was put forward.The microstructure,microhardness,and dry-sliding wear behavior of the composite coating were investigated using X-ray diffraction (XRD),scanning electron microscopy (SEM),energy dispersive spectrum (EDS) analysis,microhardness test,and ball-on-disc wear experiment.XRD results indicate that some new phases FeAl,Fe0.23Ni0.77Al,and Ni3Al exit in the composite coating with the Al2O3 addition.SEM results show that the coating is bonde...