反应等离子熔覆复合材料涂层的耐磨性研究

以Fe—Cr—C合金粉末为原料,采用反应等离子熔覆技术,在45号钢表面制得以原位生成初生相（Cr,Fe）7C3为增强相的新型陶瓷复合材料涂层。利用SEM、XRD、EDS和显微硬度计等分析了涂层的显微组织和硬度,分别在室温干滑动磨损及高温滑动磨损条件下测试了涂层的耐磨性,并讨论了其磨损机理。结果表明,涂层组织包括（Cr,Fe）7C3增强相和γ－Fe固溶体与少量（Cr,Fe）7C3构成的共晶;该涂层在室温干滑动磨损和高温滑动磨损条件下均具有优异的耐磨性。     

激光熔覆原位析出Ni-Fe-Ti-B复合涂层组织结构研究

选用合适的激光工艺参数及涂层成分,在45#钢基体表面得到了激光熔覆原位析出的Ni-Fe-Ti-B复合材料涂层.涂层中的粘结金属基体为γ-(Ni,Fe)和Nihcp,原位弥散析出相为呈现出颗粒状、细条状等分布的稳定相TiB2、Ni4B3及亚稳定相Ni2B、(Fe,Ni)3B型化合物.前两者已经细化成为纳米晶,而后两者晶粒度相对较粗.γ-(Ni,Fe)是稳定的Ni、Fe固溶体,而Nihcp形成于基体金属内部的堆垛层错作用;原位析出相产生于激光熔覆过程中涂层表面发生的原位燃烧反应或合金系快速凝固过程中的低熔点共晶作用.在基体与析出相的界面上存在高密度位错堆积,从而引起基体金属亚结构细化.     

热等离子弧熔覆合金涂层的制备与组织性能

在自制的热等离子非转移弧熔覆设备上用Stellite Ni60合金在钢的表面上进行熔覆处理。用优化后的熔覆工艺参数可以获得零稀释率的熔覆层，而且熔覆层与基体结合牢固。在对熔覆层进行化学成分，组织结构分析后发现：熔覆层可以分为三层组织结构，这三层组织结构的形成与熔池的凝固过程有关。实验结果证明，热等离子非转移弧是一种比较理想的熔覆热源。     

等离子熔覆高铬铁基涂层高温耐磨性与耐空蚀性

采用等离子熔覆工艺,以Fe-Cr-C-W-Ni复合粉末为原料;在Q235钢基材表面制备了高铬铁基复合涂层。测试了涂层的高温耐磨性和耐空蚀性。结果表明,涂层中含有大量硬质耐磨相（Cr,Fe）7C3,具有较高的显微硬度,涂层在高温干滑动磨损条件下具有优异的耐磨性能和载荷特性,经44 h空蚀试验后累积的质量损失量为0Cr13Ni6Mo不锈钢的0.497倍,具有一定的耐空蚀性能。     

氩弧熔覆原位合成TiN复合涂层的组织与耐磨性

为提高钢材料的耐磨性,以Ti、TiN和Ni60A三种粉末作为涂层材料,采用氩弧熔覆、原位合成技术,在Q235钢表面制备TiN复合涂层.利用扫描电镜（SEM）、X射线衍射仪（XRD）、显微硬度计及滑动磨损实验机（MMS-2B）对复合涂层的显微组织结构、硬度和耐磨性进行分析.结果表明：涂层主要由TiN和α-Fe组成,TiN分布均匀且与基体呈现冶金结合,涂层显微硬度最高达738.17 GPa,耐磨性为Q235钢的8倍.涂层在室温干滑动摩擦磨损条件下表现出优异的耐磨损性能,具有应用价值.     

激光熔覆金属合金和WC复合涂层及其应用

为了改善机械零件的表面性质,利用２ｋＷＣＷＣＯ２激光在金属或零件表面熔覆０．１０～１０．００ｍｍ的金属合金和ＷＣ复合耐磨涂层;并研究了其微观结构和硬度分布与熔覆工艺的关系;为了减少和避免耐磨涂层发生裂纹而设计了具有硬质相分布的“梯度涂层”,或在硬质表层和基体之间增加具有良好韧性的“过渡层”,获得了无缺陷,与基体冶金结合的优质涂层。在一些磨损零件的激光熔覆修复中,可延长使用寿命２～３倍以上。     

Nb对等离子熔覆NbC-WC/镍基复合涂层的组织性能的影响

采用等离子熔覆技术成功制备了不同(Nb+C)/WC比例的镍基复合涂层,借助高分辨扫描电镜、X射线衍射仪、显微硬度计、室温干滑动摩擦磨损试验机、三维形貌仪对复合涂层的组织及力学性能进行了表征。实验结果表明,涂层底部区域存在未熔WC颗粒,随着Nb含量的增加,WC的溶解行为得到促进;涂层由NbC、WC、γ(Fe, Ni)和M₂₃C₆组成;当n(Nb+C)∶n(WC)=2∶2时,涂层拥有较高的显微硬度(～750 HV_0.1)、较好的耐磨性能和相对光滑平整的磨损形貌;随着Nb的添加,涂层的磨损机制由粘着磨损转变为粘着磨损和磨粒磨损。     

激光熔覆生物陶瓷涂层化学冶金反应研究

研究了激光熔覆钛合金表面获得生物陶瓷涂层的化学冶金反应过程，用X-ray衍射和能谱分析方法检测了生物陶瓷涂层和涂层与界面的物相和成分分布．结果显示涂层内和涂层与基材间出现了新相，这表明其中发生了复杂的化学冶金反应．适当的激光熔覆工艺、涂层及基体的物性三者确定了化学冶金反应发生的各种条件．在这些条件作用下，涂层内合成了具有生物活性的钙-磷陶瓷，形成了牢固的界面．     

钢表面激光熔覆TiC_P/Fe基合金复合耐磨涂层

在２０钢表面用激光束熔覆了ＴｉＣ颗粒与Ｆｅ基自熔合金复合耐磨涂层。对涂层的组织、化学成分、硬度及耐磨性进行了分析。结果表明，熔覆层主要由γ－Ｆｅ，α－Ｆｅ（马氏体）和ＴｉＣ颗粒组成。为获得平整而无裂纹的表面复合涂层，随预涂覆层的ＴｉＣ量的增加，所需激光能量密度提高，复合涂层的硬度及耐磨性也随之增加。     

氩弧熔覆制备25Ni-10Zr-10Mo-15WC-40B4C复合涂层组织及耐磨性

零件表面改性技术,是提高其使用寿命的重要方法之一,以Ni粉、Zr粉、Mo粉、WC粉和B4C粉为原料,采用钨极氩弧熔覆工艺在Q235钢表面原位合成了(Fe,Mo,W)2B,(Fe,Mo,W,Zr,Ni)(B,C),(Zr,Mo,W,Fe)C0.7增强α-Fe基复合涂层。利用扫描电镜(SEM)、X射线衍射仪(XRD)、能谱分析仪(EDS)等分析手段对熔覆层的显微组织和物相进行分析,采用显微硬度测试计和摩擦磨损实验机对熔覆层的硬度及其耐磨性进行测试。结果表明:熔覆层与Q235钢基体呈良好的冶金结合,未见气孔、裂纹等缺陷。其增强相颗粒有大的圆块状、不规则长条状和小的八面体状弥散均匀地分布于基体当中;部分八面体小颗粒镶嵌在大颗粒上。复合涂层区域平均显微硬度约13.7 GPa,最高可达14.6 GPa;在室温干滑动磨损实验条件下,熔覆层呈现优异的耐磨性,其耐磨性约为基体Q235钢的20倍。     

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 beating steel contains an amount of sulfide, which can change the micro-friction mechanism and lead to a reduced friction coefficient.     

Microstructures of laser cladding of intermetallic-ceramic composite coatings

The microstructures of laser cladding of (Ni-24.5%(atom fraction)Al)+50%(mass haction)WC coatings before and after aging was comparetively studied by using SEM and TEM. It is shown that dissolving of WC and reprecipitating in the forms of WC and W₂C occurred during laser cladding, and intermetallic γ' (Ni₃Al) orderly precipitate from metastable supersaturant Ni-matrix solid solution after heat treatment. The structures are favorable for coating's properties.     

TiC/Fe cermet coating by plasma cladding using asphalt as carbonaceous precursor

A new Ti-Fe-C compound powder for plasma cladding was prepared by heating a mixture powder of ferrotitanium and asphalt pyrolyzed as carbonaceous precursor. The carbon by the pyrolysis of the asphalt acts as a reactive constituent as well as a binder in the compound powder. TiC/Fe cermet coatings were prepared by plasma cladding with the compound powder. Results show that the Ti-Fe-C compound powder has a very tight structure, which can avoid the problem that reactive constituent particles are separated during cladding. The TiC/Fe cermet coating presents a typical morphology of plasma cladding coatings with two different laminated layers: one is the composite layers in which the round fine TiC particles (<500nm) are dispersed within a Fe matrix, the other is the paragentic layers of TiC and Ti₂O₃. The coating shows high hardness and excellent wear resistance. The surface hardness of the coating is 68±5(HR30N). In the same fretting conditions, the wear area of Ni60 coating is about 11 times as much as the TiC/Fe cermet coating.     

TiC/Fe cermet coating by plasma cladding using asphalt as carbonaceous precursor

A new Ti-Fe-C compound powder for plasma cladding was prepared by heating a mixture powder of ferrotitaniurn and asphalt pyro- lyzed as a carbonaceous precursor. The carbon by the pyrolysis of the asphalt acts as a reactive constituent as well as a binder in the compound powder. The TiC/Fe cermet coatings were prepared by plasma cladding with the compound powder. Results show that the Ti-Fe-C compound powder has a very tight structure, which can avoid the problem of the reactive constituent particles being separated during cladding. The TiC/Fe cermet coating presents a typical morphology of plasma cladding coatings with two different laminated layers： one is the composite layer in which the round fine TiC particles （〈500 nm） are dispersed within a Fe matrix, the other is the paragentic layer of TiC and Ti2O3. The coating shows high hardness and excellent wear resistance. The surface hardness of the coating is 68 ± 5（HR30N）. In the same fretting conditions, the wear area of Ni60 coating is about Ⅱ times as much as the TiC/Fe cermet coating.     

Microstructure characteristics of Ni/WC composite cladding coatings

A multilayer tungsten carbide particle (WCp)-reinforced Ni-based alloy coating was fabricated on a steel substrate using vacuum cladding technology. The morphology, microstructure, and formation mechanism of the coating were studied and discussed in different zones. The microstructure morphology and phase composition were investigated by scanning electron microscopy, optical microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. In the results, the coating presents a dense and homogeneous microstructure with few pores and is free from cracks. The whole coating shows a multilayer structure, including composite, transition, fusion, and diffusion-affected layers. Metallurgical bonding was achieved between the coating and substrate because of the formation of the fusion and diffusion-affected layers. The Ni-based alloy is mainly composed of γ-Ni solid solution with finely dispersed Cr₇C₃/Cr₂₃C₆, CrB, and Ni+Ni₃Si. WC particles in the composite layer distribute evenly in areas among initial Ni-based alloying particles, forming a special three-dimensional reticular microstructure. The macrohardness of the coating is HRC 55, which is remarkably improved compared to that of the substrate. The microhardness increases gradually from the substrate to the composite zone, whereas the microhardness remains almost unchanged in the transition and composite zones.     

TiC/Fe cermet coating by plasma cladding using asphalt as a carbonaceous precursor

A new Ti-Fe-C compound powder for plasma cladding was prepared by heating a mixture powder of ferrotitanium and asphalt pyro-lyzed as a carbonaceous precursor. The carbon by the pyrolysis of the asphalt acts as a reactive constituent as well as a binder in the compound powder. The TiC/Fe cermet coatings were prepared by plasma cladding with the compound powder. Results show that the Ti-Fe-C compound powder has a very tight structure, which can avoid the problem of the reactive constituent particles being separated during cladding. The TiC/Fe cermet coating presents a typical morphology of plasma cladding coatings with two different laminated layers: one is the composite layer in which the round fine TiC particles (<500 nm) are dispersed within a Fe matrix, the other is the paragentic layer of TiC and Ti2O3. The coating shows high hardness and excellent wear resistance. The surface hardness of the coating is 68 ± 5(HR30N). In the same fretting conditions, the wear area of Ni60 coating is about 11 times as much as the TiC/Fe cermet coating.     

多弧离子镀制备的耐事故燃料包壳铬涂层晶粒结构研究

本文通过从几十微米到几埃的多尺度表征展示了多弧离子镀制备铬涂层的详细结构.经XRD, SEM, FIB, TEM和HRTEM表征,结果显示该涂层是一种多重结构,包括表面上的微米级颗粒、缺陷带钉扎的微米或次微米级液滴、以堆垛层错为晶界的柱状晶、以刃位错和螺型位错为区分的微晶、位错末端的原子畸变以及原子排列无序化的区域.这些结构通过改变涂层的结晶度,影响了晶格常数、表面粗化和FIB溅射裂纹.此外,通过分析HTEM照片,确定了这些堆垛层错和位错的类型.最后,讨论了沉积参数对这些晶粒结构的影响.     

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

<正>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 product in which a large number of coarse and fine needle-shaped TiB and a few equiaxial TiC particles are homogeneously embedded.A thin dilution zone with a thickness of about 100μm is present at the interface,and it consists of a few TiB and TiC reinforcements and a large number of lamella grains growing parallel to the heat flux direction in which a thin needle-shaped microstructure exists due to the martensitic transformation. The microstructural evolution can be divided into four stages:precipitation and growth of primaryβ-Ti phase,formation of the binary eutecticumβ-Ti+TiB,formation of the ternary eutecticumβ-Ti+TiB+TiC,and solid transformation fromβ-Ti toα-Ti.     

Bonding mechanism and performance of ceramic coatings by sol-gel process

Thin alumina coatings were prepared on carbide tools to enhance their wear-resistant ability by dip coating from an aluminum alkoxide solution. The coating eventually obtained was perfectly integrated, without any macroscopic defect, and showed good performance in turning medium carbon steel, which presented a novel and promising coating method for cutting tools. The coating morphology before and after heat treatment was examined with the aid of a scanning electron microscope (SEM). The composition of coating and interface layer as well as the crystal structure of coating was characterized by X-ray diffraction (XRD). The elemental distribution near the interlayer was analyzed by electron probe microanalysis (EPMA).     

Microstructure and mechanical properties of Ni-based composite coatings reinforced by in situ synthesized TiB2 + TiC by laser cladding

A Ni-based composite coating reinforced by in situ synthesized TiB₂ and TiC particles was fabricated on Ti6Al4V by laser cladding. An attempt was made to correlate the thermodynamic predictions and experimental observation. The microstructure and the microhardness profile across the coating were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and a hardness tester. It is found that the coating mainly consists of a large number of reinforcements (black blocky TiB₂, flower-like or equiaxial TiC, and fine acicular CrB) and the γ matrix. The hardness of TiB₂, TiC, and CrB reinforcements is much higher than that of the γ matrix. The dispersive distribution of such high hardness reinforcements causes the increase in hardness of the whole coating. The average value of the hardness is approximately Hv_0.2 700 in the coating. The hardness of the coating is obviously higher than that of the substrate due to the dispersion strengthening of reinforcements.