激光熔覆Cr3C2/Ni基复合涂层的磨削特性

为研究不同磨削参数、不同质量分数及粒度的Cr_3C_2对激光熔覆Cr_3C_2/Ni基复合涂层磨削表面质量的影响规律,探究其磨削特征及磨削表面缺陷的形成机理,采用CBN砂轮对激光熔覆Cr_3C_2/Ni复合涂层进行磨削实验.实验结果表明:Cr_3C_2/Ni基复合涂层磨削表面的加工缺陷主要产生于Ni合金基体中形成的堆积、犁沟、局部崩碎、裂纹,以及破碎的Cr_3C_2颗粒和由于破碎的Cr_3C_2脱落、被压碎的Cr_3C_2颗粒产生的表面凹坑等.在较小的切深和较低质量分数的Cr_3C_2条件下,Ni合金基体中较容易形成堆积;随着切深的增加,Ni合金基体中的犁沟加深,局部出现崩碎;当涂层中的Cr_3C_2质量分数高于20%时,Ni合金基体中甚至出现裂纹;涂层中Cr_3C_2质量分数达到30%时,磨削表面出现较多破碎的Cr_3C_2和凹坑.在相同的磨削参数下,涂层磨削表面粗糙度随着熔覆层中Cr_3C_2粒径的增大而增大,随着Cr_3C_2质量分数的增加而降低,但Cr_3C_2质量分数超过20%时,涂层的粗糙度反而略有上升.减小Cr_3C_2的粒径和提高砂轮的线速度可以减少涂层磨削缺陷的产生.     

Al2O3大气等离子喷涂层的磨损特性

利用球－盘接触式摩擦磨损试验机，在室温、大气和润滑磨擦条件下研究了Al2O3涂层／NiCr粘结涂层与Al2O3涂层的摩擦磨损特性，并用拉伸试验方法测定了涂层与基体之间的粘结强度。结果表明，Al2O3涂层／NiCr粘结涂层的耐磨性能比Al2O3涂层好；基体的表面粗糙度对涂层的粘结强度影响较大；本研究试验条件中对磨损特性最佳的涂层厚度为300μm；Al2O3涂层／NiCr粘结涂层的磨损机理受残余应力的影响很大；粘结喷涂在减少涂层中的残余应力起着很重要的作用。     

Cr3C2对激光熔覆Ni基合金涂层组织与性能的影响

采用激光熔覆技术在低碳钢表面制备Ni基合金涂层(Ni50)及添加30％Cr3C2(质量分数)的Ni基复合涂层(Cr3C2/Ni).利用光学显微镜(OP)、扫描电镜(SEM)及X射线衍射仪(XRD)研究2种涂层的微观组织特征和相结构;通过显微硬度以及滑动磨损试验分析两种涂层的硬度和耐磨损性能.结果表明:Ni50合金涂层组...     

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.     

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．     

真空熔覆原位自生W_xC/Ni基复合涂层的组织及耐磨性能

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_xC/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W_xC、(Cr,Fe)_7C_3和Cr_7C_3相组成,且W_xC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.     

AT13/WS2复合涂层的制备及摩擦学性能

采用等离子喷涂技术和水热反应合成法制备Al₂O₃–13%Ti O₂(AT13)陶瓷涂层和AT13/WS₂复合涂层,利用多功能摩擦学试验机和原子力显微镜,研究原位合成的WS₂对AT13陶瓷涂层表面摩擦磨损性能的影响,且利用场发射扫描电子显微镜(FESEM)、能谱仪(EDS)和X射线衍射仪(XRD)对AT13/WS₂复合涂层物相组成和微观形貌进行分析,探讨材料的磨损机理。结果表明：通过水热反应,可将WS₂粉末合成在AT13涂层表面微裂纹和孔隙中,制得AT13/WS₂复合涂层;在干摩擦测试条件下复合涂层的摩擦系数(0.2左右)相对AT13涂层(0.7左右)显著降低;在微观尺度下AT13涂层横向摩擦力(0.5 V)明显大于AT13/WS₂复合涂层(0.1 V);严重的磨粒磨损和脆性剥落是AT13涂层磨损的主要原因,WS₂的引入可改善AT13涂层的磨损情况,AT13/WS     

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.     

NiAl/Al复合涂层高温抗氧化性能与扩散机制

为了延长纯钛在高温环境下的工作寿命,采用电弧喷涂方法在纯钛表面制备了NiAl/Al复合涂层.在热处理炉中进行800 ℃×50 h连续氧化实验,根据NiAl层与纯Al层反应生成的金属间化合物性能,考察涂层的高温抗氧化行为和高温防护机制.结果表明,复合涂层在体系中具有足够的Al、Ni元素,可在涂层外表面形成以Al₂O₃为主的氧化物防护层,从而阻碍氧向内侵入.在高温氧化过程中NiAl/Al涂层中的Al发生熔化扩散,并与Ni和Ti形成以NiAl、Ni₂Al₃、NiAl₃及TiAl₃富Al相为主的扩散阻挡层.NiAl/Al复合涂层显著提高了纯钛的高温抗氧化能力.     

TA1表面制备Ni/Al涂层的反应扩渗及抗氧化行为

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涂层.对试件进行900 ℃×5 h热处理后,再进行900 ℃×40 h连续氧化实验,探索其高温抗氧化行为.结果表明,经过表面改性处理的Ni/Al涂层可以显著提高纯钛的高温抗氧化性.在热处理过程中Ni/Al涂层中的Al发生熔化扩散并与Ni和Ti形成以NiAl与TiAl₃相为主的扩散层.在氧化过程中Ni/Al涂层表面形成连续且致密的α-Al₂O₃,同时表面扩散层中的富铝相可为涂层表面提供充足的Al元素,进而对纯钛基体提供有效的高温抗氧化保护作用.     

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     

PTA clad （Cr, Fe）7C3/γ-Fe in situ ceramal composite coating

A wear-resistant （Cr, Fe）7C3/γ-Fe in situ ceramal composite coating was fabricated on the substrate of 0.45wt%C carbon steel by a plasma-transferred arc cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness, and dry-sliding wear resistance of the coating were evaluated. The results indicate that the microstructure of the coating, which was composed of （Cr, Fe）7C3 primary phase uniformly distributed in the γ-Fe, and the （Cr, Fe）7C3 eutectic matrix was metallurgically bonded to the 0.45wt%C carbon steel substrate. From substrate to coating, the microstructure of the coating exhibited an evident epitaxial growth character. The coating, indehiscent and tack-free, had high hardness and appropriate gradient. It had excellent wear resistance under the dry sliding wear test condition.     

等离子堆焊镍基合金粉末的组织与性能

为了提高核电成套设备的阀体性能,利用光学显微镜、扫描电子显微镜、X射线衍射仪、电子探针显微分析仪和能谱仪分析了堆焊层的组织形态和成分分布,利用显微硬度计测量了堆焊层的硬度,利用磨损试验机分析了堆焊层的耐磨性.结果表明,堆焊层主要由过共晶组织组成,从熔合线到堆焊表面堆焊层组织依次为平面晶生长区、亚共晶组织区、共晶组织区和过共晶组织区.堆焊层金属相由γ-Ni、CrB、Cr_2B、Cr_7C_3和Cr_(23)C_6组成,初晶相由硼化物(CrB或Cr_2B)和碳化物(Cr_7C_3或Cr_(23)C_6)组成,而共晶组织主要由富(Ni,Fe)奥氏体固溶体或富Ni奥氏体固溶体组成.堆焊层表面平均硬度达到50 HV以上,约为基体硬度的3~5倍,与母材相比堆焊层的耐磨性约提高了9倍.     

化学气相沉积法制备碳化铬薄膜的研究

以三（2,2,6,6-四甲基-3,5-庚二酮）化铬为前驱体,采用化学气相沉积（CVD）法在氧化铝（Al₂O₃）陶瓷基板上制备碳化铬（Cr₃C₂）薄膜,其中沉积温度为723 K至923 K,沉积时间为1 200 s。研究了不同沉积温度对Cr₃C₂薄膜的相组成、择优取向、宏观表面、微观结构及电学性能的影响。结果表明,在723 K至923 K下制备得到具有高度（130）择优取向的Cr₃C₂薄膜。随着沉积温度的升高,Cr₃C₂薄膜表面先由光滑变粗糙,后逐渐变光滑;薄膜晶粒呈椭球型生长;薄膜的厚度先增加后减小,从而导致电阻先减小后增大。在798 K时制备得到厚度最大且电阻最小的（130）择优取向的最佳Cr₃C₂薄膜。同时,在实验条件下Cr₃C₂薄膜表面存在少量的碳和Cr₂O₃。     

Microstructure and tribological properties of laser clad Ni-Ag/Tic composite coating

Ni-Ag/TiC composite coating was prepared on the 45 steel substrates by means of laser cladding. Microstructure and wear properties of composite coatings were analyzed using optical microscopy, field emission scanning electron microscopy and wear machine. The experimental results show that defects, such as cracks and pores, do not occur in the laser-cladded Ni-Ag/TiC composite coating and 45 steel substrate, and they present good metallurgical bonding between them. Compared with Ni/TiC composite coating, micro- hardness values of the two coatings do not present evident differences. The wear experiment result shows that Ni-Ag/TiC composite coated with Ag possesses low friction coefficient and good wear resistance compared with Ni/TiC composite coating.     

NiCr-Cr3C2 陶瓷涂层在锌铝腐蚀中的失效分析

运用超音速火焰喷涂技术在304不锈钢沉浸辊上喷涂NiCr-Cr₃C₂ 陶瓷涂层。将制备后的试样置于600℃铝质量分数为55%的熔融锌铝混合液中,并分析涂层在其中的腐蚀机理和失效过程。采用SEM 观察了原始粉末的形态并对涂层被腐蚀前后的形貌进行对比观察,采用EDS检测了NiCr-Cr₃C₂ 粉末的原始构成以及涂层被腐蚀后其中的元素变化。结果表明,NiCr-Cr₃C₂ 陶瓷涂层的孔隙率为2.9%,平均结合强度为82.76MPa,显微维氏硬度的平均值为1078.67HV。NiCr-Cr₃C₂ 陶瓷涂层在被沉浸1d后,在涂层中发现了元素构成的变化且有层次区分,NiCr-Cr3C2 涂层失效原因是Ni-Cr基体被Zn溶解,导致了涂层溃散,涂层中的Cr₃C₂也同时失去保护作用,并漂移到Zn-Al熔体中。     

Morphology and tribological properties of Ni/n-SiO2 composite coatings by pulse-reverse current brush-plating

Ni/n-SiO₂ composite coating was electrodeposited by brush-plating with pulse-reverse current(RC). The morphology, hardness, and tribological properties of the coating were investigated and compared with those of Ni and composite coatings electrodeposited with direct current (DC). The results indicate that Ni/n-SiO₂ composite coating electrodeposited by RC, because of RC and the nano powders, has denser coating, finer crystal grains, higher hardness (HV650.0, nearly 1.5 times higher than that of Ni coating electrodeposited by DC) and lower friction coefficient (nearly 0.62), as a result, in the wearing experiment, the Ni/n-SiO₂ composite coating electrodeposited by RC has the least worn loss. So this kind of coating has better wear resistance. And RC electro brush-plating can be used as a new technology of brush-plating in the area of wear resistance. Foundation item: Project (50235030) supported by the National Natural Science Foundation of China; Project (51489020104JS9102) supported by the National Key Laboratory for Remanufacturing     

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…     

高能脉冲类激光熔覆镍基合金层的组织及性能

为了提高304不锈钢表面的综合性能,采用高能脉冲类激光熔覆沉积技术在304不锈钢表面制备了镍基合金熔覆层.采用扫描电子显微镜、能谱仪、X射线衍射仪、销-盘磨损试验机与电化学测试系统对镍基合金熔覆层的显微组织、相结构、耐磨损性能和电化学腐蚀性能进行了研究.结果表明,镍基合金熔覆层与304不锈钢基材呈良好的冶金结合,熔覆层的相对耐磨损性为304不锈钢基材的4.4倍.熔覆层组织由γ-Ni基体相、Ni_3Mo、Fe_7Mo_3和Cr_(23)C_6碟状增强相与不规则棒状增强相组成.增强相是提高耐磨损性能的主要原因,增强相与基体相的电极电位差是导致腐蚀电流密度增加的主要原因.     

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.