20#钢表面镍基添Y2O3激光熔覆层及其高温磨损行为

采用激光熔覆法,在20#钢表面制备出添Y2O3的镍基合金粉末的熔覆涂层．分析了熔覆层的相组成、高温耐磨性能;观察了熔覆层显微形貌．结果表明：所制得的熔覆层组织均一、致密,与基体形成了良好的冶金结合．添加Y2O3的熔覆层硬度提高到基体的3．9倍,高温耐磨率仅是基体的1／4．熔覆层耐磨能力增强的主要原因是熔覆层与基体良好的冶金结合,镍基合金良好性能,组织细化以及硼化物、硼碳化物等析出相的强化作用．     

氩弧熔覆原位自生Ti(C、N)-WC增强Ni60A复合涂层的研究

以Ni60A、TiC、TiN、WC、Co粉为原料,在Q235钢的表面用氩弧熔覆原位合成技术制备了Ti(C、N)-WC增强镍基复合材料涂层.研究了涂层的显微组织、化学成分、硬度变化和摩擦磨损特性.熔覆层组织主要由富Ni的γ(Ni,Fe)相、Ti(C、N)、WC和(Fe,Cr)xC等组成.涂层的显微硬度和耐磨性分别是基体Q235钢的6.5倍和10倍.显微硬度由表及里呈先上升后下降的阶梯状趋势,到热影响区时又明显降低.基体Q235钢的磨损机制为黏着磨损和磨料磨损,而复合涂层的的磨损形式主要是磨屑充当第三体引起的磨粒磨损.     

激光熔覆功率对原位合成TiB/TiN涂层组织和摩擦性能的影响

以光学显微镜(OM)、X射线衍射分析(XRD)、扫描电子显微镜(SEM)和电子探针(EPMA)方法分析涂层相组织结构和显微形貌,采用硬度测试仪及滑动磨损机测试涂层硬度及耐磨性能.结果表明,涂层中原位合成了TiB和TiN强化相颗粒,分别呈现针棒状形貌组织和等轴晶形貌组织;激光功率对组织形貌影响较大,随着激光功率的提高,熔覆层的硬度和耐磨性能呈上升的趋势;母材的磨损机制主要为疲劳磨损,而熔覆层金属的磨损主要由疲劳磨损和磨粒磨损共同作用,其中磨粒磨损占主体作用.     

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。     

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。     

激光熔覆纳米La2O3/Ni基合金涂层

采用横流5kWCO2激光在低碳钢基体表面制备纳米La2O3/Ni基激光熔覆涂层。采用光学显微镜（OP）、扫描电子显微镜（SEM）、X射线衍射仪（XRD）分别对熔覆涂层进行显微组织和相组成的观察。用显微硬度计和滑动磨损试验机对熔覆涂层的硬度和耐磨性进行测试。试验结果表明：熔覆层主要由γ-（Ni,Fe）,Cr23C6,LaNi10.5Si2.5等相组成,随离结合面距离增大,熔覆层的组织逐渐变细。随着纳米La2O3加入量及扫描速度增加,熔覆层组织变细。加入纳米La2O3后,平均硬度由未加时500HV0.5提高到约700HV0.5,耐磨性也得到不同程度的提高。在本试验条件下,添加质量分数为1.0%纳米La2O3熔覆层的耐磨性明显高于质量分数为1.5%纳米La2O3熔覆层的耐磨性。扫描速率采用250mm/min的熔覆层,其综合性能最佳。     

激光熔覆原位合成TiB2/Cu复合材料涂层及其导电性

应用500WYAG固体激光器，在纯铜表面成功的原位合成了TiB2／Cu复合材料层．实验结果表明，激光熔覆TiB2／Cu复合材料层组织完好，熔覆复合材料层与铜基体呈良好的冶金结合．熔覆层内。TiB2颗粒细小均匀，颗粒尺寸约为300～500nm．经四探针法测量，激光熔覆TiB2／Cu复合材料层的电导率可达82％IACS。     

激光熔覆Co基合金/MoSi_2复合涂层显微组织分析

在304不锈钢表面预置Co基合金和MoSi2混合粉末,采用激光熔覆技术制备Co基合金/MoSi2复合涂层.利用光学显微镜、扫描电镜、电子探针和X衍射仪对熔覆层显微组织进行分析,并测试其显微硬度.结果表明熔覆层与基体呈良好的冶金结合.熔覆层中存在两种明显不同的凝固特征：一是MoSi2的添加量在0～20%之间,涂层组织主要由柱状树枝亚共晶和枝晶间共晶组成;二是MoSi2的添加量在30%～80%之间时,涂层组织主要是形貌各异的小平面树枝过共晶组成如竹叶状、星状、蝴蝶状、花瓣状等.其中Co基合金/40wt.%MoSi2复合涂层的平均显微硬度达到最大值1 455 HV0.2,是基体材料的4.9倍.     

316L不锈钢激光熔覆层的组织及硬度分析

在304不锈钢表面预置316L不锈钢粉末,采用CO2激光器熔覆制备316L粉末涂层.观察了激光熔覆表面形貌的成形质量,研究了不同工艺参数对熔覆层微观组织、显微硬度和材料成分的影响.结果表明:熔覆涂层无明显裂纹、气孔等缺陷,与基材结合良好;熔覆层是由细小等轴晶和柱状晶组成,且当激光功率为1.5 kW时,奥氏体晶粒更加均匀、细小;激光功率对熔覆层的显微硬度影响不大,激光熔覆前后,组织成分(质量分数,全文同)没有明显变化,316L不锈钢熔覆粉末适用于304不锈钢基材的修复.     

H13钢激光熔覆钴基复合涂层的组织及耐磨性

采用5kW连续CO_2激光器,在H13热作模具钢表面进行激光熔覆Stellite-6(简称St6)、St6+5%WC、St6+5%WC+1%RE钴基合金复合涂层。采用光学显微镜、扫描电子显微镜、X射线衍射仪、显微硬度计及磨损试验机,对熔覆层的显微组织、元素分布、相组成、显微硬度及磨损性能等进行了系统研究。结果表明,激光熔覆层与基体为冶金结合,各熔覆层的基体相组织为γ-Co、γ-Ni,增强相组织均包括Cr-Ni-Fe-C、(Mn,Cr)_7C_3、Cr_(23)C_6等相,此外,St6+5%WC和St6+5%WC+1%RE熔覆层的增强相中增加了WC、W_2C和SiC相;熔覆层显微硬度HV_(0.2)为560~710HV;摩擦磨损试验结果表明,在相同条件下,耐磨性能由高到低依次是St6+5%WC+1%RE、St6+5%WC、St6、H13钢。     

TiB2/Cu复合材料组织与性能的研究

以Ti、B和Cu的单质粉末为原料,经混粉-冷压成形-真空烧结,制备出原位自生TiB2陶瓷颗粒增强铜基复合材料.并借助热分析方法和X射线衍射对增强颗粒进行分析,同时通过扫描电子显微镜对复合材料组织进行观察,进一步测定复合材料的力学性能.结果表明,在Ti-B-Cu体系中,通过原位反应生成增强相是TiB2.随着B粉和Ti粉含...     

Microstructural evolution of titanium matrix composite coatings reinforced by in situ synthesized TiB and TiC by laser cladding

Titanium-based composite coatings reinforced by in situ synthesized TiB and TiC particles were successfully fabricated on Ti6Al4V by laser cladding using Ti-B_4C-Al or Ti-B_4C-C-Al powders as the precursor materials.The microstructural and metallographic analyses were made by X-ray diffraction(XRD),optical microscope(OM),scanning electron microscopy(SEM),and electron probe microanalysis (EPMA).The results show that the coatings are mainly composed ofα-Ti cellular dendrites and a eutectic transformation p...     

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.     

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.     

Synthesis of Titanium Carbide Particle in Laser Melted-pool in situ

The titanium carbide phase was synthesized in laser melted-pool in situ as the reinforced particles of nickel based composite coating on Ti-6 Al-4 V alloy surface using the nickel and graphite blending powder by laser cladding. The microstructure investigation showed that the petals-shaped particles and granular particles were two main morphology of titanium carbide particles. And a few spiral-shaped titanium carbide pattern and eutectic titanium carbide appeared on the cross-sections of the coating. The spiral-shaped titanium carbide pattern composed of some slender arc-shape titanium carbide particles and the eutectic titanium carbide was fine. The morphology and distribution of the spiral-shaped titanium carbide patterns and eutectic titanium carbide confirmed that their growth mechanism was the dissolution-precipitation mechanism and was affected by the convection behavior of the laser melted pool. The spiral-shaped titanium carbide pattern would precipitate out the high-temperature melts under high-speed convection. The eutectic titanium carbide would precipitate out when the melts stopped convection or dropped to eutectic temperature.     

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.     

激光熔覆铜基自生复合材料设计及其涂层研究

为了提高铝合金的耐磨性，利用铜合金体系存在液相分离现象等冶金性质，在铝合金表面设计了自生铜基复合材料体系，并采用激光熔覆技术对其进行了验证和优化。设计的较理想材料体系为Cu-16Ni-6Fe-8Co-7Mo-4Cr-3Si，由其得到的激光熔覆复合材料中存在大量的自生硬质颗粒增强体，其熔覆涂层具有良好耐磨性，其耐磨性甚至优于汽车发动机缸盖阀门座圈QZ5铸铁合金。     

Ti对激光熔覆铁基合金涂层组织和耐磨性的影响

采用激光熔覆技术在低碳钢表面制备Fe基合金涂层（Fe50）和添加1％（质量分数）Ti粉的Ti／Fe50涂层,分析研究两涂层的相结构、显微组织、硬度及耐磨性。结果表明：激光熔覆Fe50涂层主要由α-Fe和Cr23C6组成,其组织由柱状枝晶固溶体及其间网状分布的共晶组成;添加质量分数为1％的Ti后,涂层中除了α-Fe和Cr23C6相,还含有γ—Fe相,组织明显等轴化、均匀化;与Fe50涂层相比,Ti／Fe50涂层耐磨性提高了20％以上。     

真空熔覆原位自生WC/Ni基复合涂层的组织及耐磨性能x

为了提高煤油泵的使用寿命,利用真空熔覆技术在316L不锈钢表面原位合成了W_{C/Ni基复合涂层.采用扫描电子显微镜、能谱仪、X射线衍射仪研究了复合涂层的显微组织和相组成,并对其进行了硬度测量和摩擦性能试验.结果表明,复合涂层组织细密且与基材呈冶金结合.复合涂层主要由γ-Ni固溶体、原位生成的WC、(Cr,Fe)7C3和Cr7C3相组成,且WC相弥散分布在γ-Ni固溶体中.复合涂层的硬度约为316L不锈钢基材的4倍,相对耐磨性约为基材的37倍.xx}x