ZrO2纳米粉等离子喷涂层制备研究

经二次造粒的纳米ZrO2为喂料制备了等离子喷涂层。X衍射物相分析、SEM形貌观察表明．涂层主要以四方相和立方相构成，含有少量的单斜相；在喷涂过程中粉未熔化状况良好，涂层含有网状微裂纹。用金相法测定了涂层孔隙率，与普通ZrO2等离子喷涂层相比，涂层敛密度显著提高。在模拟熔炼条件下，对涂层进行了真空热震试验，涂层均能经受一次真空热震而涂层完好、单斜相含量较低、具有一定孔隙率和均匀网状微裂纹的涂层，经二次真空热震后，涂层仍处于完好状态。     

Fabrication and Wear Behavior of Nanostructured Plasma-Sprayed 6061Al-SiCp Composite Coating

6061Al powder with 15 wt.% SiC particulate (SiC_p) reinforcement was mechanically alloyed (MA) in a high-energy attrition mill. The MA powder was then plasma sprayed onto weathering steel (Cor-Ten A242) substrate using an atmospheric plasma spray process. Results of particle size analysis and scanning electron microscopy show that the addition of SiC particles as the reinforcement influences on the matrix grain size and morphology. XRD studies revealed embedment of SiC_p in the MA-processed composite powder, and nanocrystals in the MA powder and the coating. Microstructural studies showed a uniform distribution of reinforced SiC particles in the coating. The porosity level in the coating was as low as 2% while the coating hardness was increased to 232VHN. The adhesion strength of the coatings was high and this was attributed to higher degree of diffusion at the interface. The wear rate in the coatings was evaluated using a pin-on-disk type tribometer and found to decrease by 50% compared to the 6061Al matrix coating. The wear mechanism in the coating was delamination and oxidative type.     

Microstructure and Tribological Property of TiC-Mo Composite Coating Prepared by Vacuum Plasma Spraying

TiC-based composite coating using Mo as an additive has been fabricated by vacuum plasma-spraying, and then the phase composition and microstructure of TiC-Mo composite coating were investigated. Wear resistance of the TiC-Mo composite coating was comparatively studied with pure TiC coating. The experimental results showed that the microstructure of the TiC-Mo composite coating was relatively homogeneous and compact, exhibiting typical lamellar structure of plasma-sprayed coating. Orientated columnar grains of TiC can be found in the composite coating, and a (Ti, Mo)C transition phase was also observed. Due to the formation of (Ti, Mo)C transition phase, strong interface between TiC and Mo splats was obtained, which positively influenced the wear performance of the composite coating. As compared with pure TiC coating, the TiC-Mo composite coating exhibited improved wear resistance both at low and high loads. Wear mechanisms for the TiC coatings have been changed by adding Mo element.     

Fabrication and Characterization of Plasma-Sprayed Carbon-Fiber-Reinforced Aluminum Composites

Carbon fiber (C_f)/Al specimens were fabricated by plasma-spraying aluminum powder on unidirectional carbon fiber bundles (CFBs) layer by layer, followed by a densification heat treatment process. The microstructure and chemical composition of the C_f/Al composites were examined by scanning electron microscopy and energy-dispersive spectrometry. The CFBs were completely enveloped by aluminum matrix, and the peripheral regions of the CFBs were wetted by aluminum. In the wetted region, no significant Al₄C₃ reaction layer was found at the interface between the carbon fibers and aluminum matrix. The mechanical properties of the C_f/Al specimens were evaluated. When the carbon fiber volume fraction (CFVF) was 9.2%, the ultimate tensile strength (UTS) of the C_f/Al composites reached 138.3 MPa with elongation of 4.7%, 2.2 times the UTS of the Al matrix (i.e., 63 MPa). This strength ratio (between the UTS of C_f/Al and the Al matrix) is higher than for most C_f/Al composites fabricated by the commonly used method of liquid-based processing at the same CFVF level.     

TC4合金表面激光熔覆B4C及B4C＋Ti粉末涂层的微观组织

利用XRD，SEM和EDS分析手段对B4C和B4C＋10％Ti（质量分数，下同）激光熔覆层的微观组织进行了分析。结果表明，TC4合金表面B4C与B4C＋10％Ti激光熔覆层的组成相基本相同，均由TiC1-x，TiB，TiB2和Ti相组成，说明在TC4合金表面熔覆过程中有一部分Ti进入熔覆层并与B4C发生化学反应原位生成了TiB，TiB2和TiC1-x相。TiC1-x相以树枝状相形式存在，TiB2相以粗大须状相形式存在，TiB相以细小须状相形式存在。熔覆层与基底结合良好，没有发现裂纹与孔洞。基底热影响区呈淬火组织形貌，为典型的针状马氏体组织特征。与B4C激光熔覆层相比，B4C＋10％Ti激光熔覆层的组织细小，TiB相含量增多，TiB2相含量减少。     

TC4合金表面纳米晶涂层的摩擦学性能研究

通过双阴极等离子技术在TC4合金表面制备了不同铬含量的纳米晶体涂层,并研究了纳米晶涂层的摩擦磨损性能。结果表明,机械用材料表面纳米晶涂层与基体结合的紧密程度与涂层组织的均匀性和致密性密切相关。纳米涂层的弹性模量以及涂层的硬度随着纳米晶涂层中铬含量的增加而增加,而磨损率和摩擦因数均降低。     

可加工B4C/BN复相陶瓷的制备与性能研究

采用热压烧结工艺制备了B4C/BN可加工复相陶瓷,热压烧结工艺参数为热压温度为1850℃,热压压力为30 MPa,保温时间为1 h.通过向B4C基体中加入不同含量的h-BN来研究h-BN的含量对所制备的B4C/BN复相陶瓷材料的力学性能和可加工性能的影响,并通过XRD和SEM来研究复相陶瓷的物相组成和显微结构.结果表明随着复相陶瓷中的h-BN含量的增加,B4C/BN复相陶瓷的密度逐渐降低;B4C/BN复相陶瓷的抗弯强度和断裂韧性有所降低;复相陶瓷的维氏硬度大幅度降低;而硬度的降低导致了复相陶瓷的可加工性能得到显著的提高,当h-BN的含量高于20%(质量分数,下同)时,B4C/BN复相陶瓷具有良好的可加工性能.     

Microstructure and Pitting Corrosion Behavior of Plasma-Sprayed Fe-Si Nanocomposite Coating

In this study, Fe-Si nanoparticle composite coating (FSN) and Fe-Si microparticle composite coating (FSM) were prepared via atmospheric plasma spraying, and FSN was thermally treated under hydrogen atmosphere at 1120 °C for holding time of 2.5 h (TFSN). Under transmission electron microscopy, many unmelted nanoscale particles were observed in FSN, while no substantial particles were found in TFSN. On scanning electron microscopy analysis, pores and cracks were observed in FSM and FSN, while no defects were found in TFSN. Scanning electrochemical microscopy testing in 3.5 wt.% NaCl for 5 h revealed that FSM underwent severe pitting corrosion, FSN showed relatively minor pitting corrosion, and TFSN had no pitting corrosion.     

The Tribological Behavior of Plasma-Sprayed Al-Si Composite Coatings Reinforced with Nanodiamond

Al-Si composite coatings reinforced with 0?vol.%, 0.5?vol.%, and 2?vol.% nanodiamond were synthesized by plasma spraying. The effect of the addition of nanodiamond on the microstructure, hardness, and tribological performance of the composite coatings is investigated. The addition of 2?vol.% nanodiamond results in 45% improvement in the wear resistance of Al-Si coating. Al-Si coating with 0.5?vol.% nanodiamond exhibited lower coefficient of friction (0.45) with a 12% improvement in the wear resistance. Plasma-sprayed AlSi coatings with nanodiamond have excellent potential as wear-resistant coatings in automotive applications.     

镁合金表面等离子喷涂Al涂层及激光重熔研究

利用等离子喷涂技术在镁合金表面制备了Al涂层,并通过激光对该涂层进行重熔处理。利用SEM、金相显微镜、XRD、万能材料试验机、盐雾腐蚀试验等分析测试手段研究了该涂层在激光重熔前后的变化。结果表明:镁合金表面等离子喷涂Al涂层经激光重熔后,涂层和基体之间的结合由机械结合转变为冶金结合,结合强度由20.96MPa提高到22.13MPa;涂层相组成不变;但出现了较多的孔隙和空洞,孔隙率由4.6%增大到7.5%,涂层耐盐雾的时间由900h降低到264h。     

温度对B4C涂层氧化防护性能和防护机制的影响

目的 研究温度对B4C涂层氧化防护性能和防护机制的影响,得出B4C涂层最佳氧化防护温度范围,以及B4C涂层在不同温度的氧化防护机制演变。方法 以石墨为基体,采用放电等离子烧结法在石墨表面制备B4C涂层,通过不同恒温氧化试验(800、1 000、1 200、1 400 ℃)和室温至1400 ℃宽温域动态氧化试验来测试其氧化防护性能,并通过X射线衍射(XRD)、扫描电子显微镜(SEM)和能谱仪(EDS)对B4C涂层石墨试样氧化前后的物相组成、微观形貌、氧扩散等进行分析。结果 B4C涂层氧化后可生成B2O3玻璃膜,在800、1 000、1 200、1 400 ℃恒温氧化的防护效率分别为98.43%、98.61%、94.4%和92.8%,在室温至1 400 ℃宽温域动态氧化的防护效率为93.1%。B4C涂层在800 ℃以下主要依赖结构阻氧,800至900 ℃由结构阻氧向惰化阻氧转变,900 ℃以上主要依赖惰化阻氧。1 100 ℃以上,随温度升高B2O3玻璃膜的挥发加剧,B4C涂层惰化阻氧能力减弱。结论 B4C涂层的氧化防护效率随温度上升先增大后减小,结构阻氧机制逐渐降低,惰化阻氧机制先升高后降低。B4C涂层在800至1 100 ℃具有良好的氧化防护性能。     

B4C含量对B4C增强Ni基合金钎涂层的影响

为提高低碳钢的表面性能,以Ni基合金为原材料,添加一定量的B4C粉末作增强相,钎涂于低碳钢表面,研究了B4C添加量对涂层性能的影响.结果表明:控制合理的工艺参数,可以获得表面平整、光滑,与基体呈冶金结合的涂层;随着B4C添加量的增加,涂层的硬度及耐磨性也逐渐增加,但添加量增加到一定值后,涂层与基体的熔合效果不佳,出现气孔等缺陷,硬度及耐磨性反而下降.     

低合金钢表面Fe基B4C耐磨涂层组织与性能

目的在低合金结构钢表面制备一层高硬度、高耐磨的铁基陶瓷颗粒增强层,并研究熔覆层的微观结构及性能。方法利用等离子熔敷技术,在16Mn钢基体上熔敷Fe58合金粉与B_4C陶瓷粉的混合粉末。结果在16Mn钢表面成功制备了高硬度、高耐磨的铁基陶瓷颗粒增强层,陶瓷颗粒增强层致密、均匀、无气孔、无裂纹,且与基体结合良好。XRD及SEM结果表明,熔覆层生成了细小、均匀的碳、硼化物增强相,熔覆层与基体的相容性好,界面呈冶金结合,熔覆层的增强相主要有Fe2B、FeB、Cr7BC4、Cr7C3及B_4C相,Fe与B的化合物Fe2B、FeB呈链状沿晶界分布在(Fe,Ni)固溶体上,并与(Fe,Ni)固溶体在晶界形成网状结构。铬的碳、硼化物Cr7BC4和Cr7C3及未完全反应的B_4C陶瓷相,则呈不规则块状和点状在晶内弥散分布。熔覆层断面的显微硬度及表面磨粒磨损测试结果表明,熔覆层断面的显微硬度分布均匀,平均硬度可达11.9GPa,是16Mn钢基体的7.95倍,耐磨粒磨损性能是基体的7倍以上。结论晶内弥散分布的B_4C、Cr7BC4和Cr7C3硬质相与晶界成链状分布的Fe2B、FeB共同作用,使熔覆层的硬度、耐磨性明显提高。     

不同摩擦参数下NiCr-Cr3C2涂层摩擦学性能研究

采用超音速等离子喷涂工艺制备了NiCr-Cr3C2涂层,研究了摩擦副、载荷、摩擦频率等不同摩擦条件对涂层摩擦学性能的影响。结果表明:超音速等离子制备的NiCr-Cr3C2涂层均匀致密,具有较高硬度;摩擦副和载荷对摩擦系数有较大影响,摩擦频率对摩擦系数影响较小。     

TC4钛合金表面镀Cu摩擦磨损性能的研究

利用硫酸盐镀铜技术在TC4钛合金表面电镀制备Cu镀层,采用SEM、EDS和STM等方法研究TC4钛合金基体及其镀Cu层的摩擦磨损性能,分析其磨损率、摩擦系数和磨痕形貌,探讨其磨损机理。结果表明:TC4钛合金表面镀Cu可以显著地改善和提高其表面耐磨性,Cu镀层的耐磨性明显地优于TC4钛合金基体;TC4钛合金基体的磨痕呈犁沟形貌,磨损机理为剥层磨损和黏着磨损;镀Cu层的磨痕呈现的是附着的塑性变形后铜磨屑形貌,磨损机理为剥层磨损和疲劳磨损。     

TC4钛合金表面镀Cu摩擦磨损性能的研究

采用一种反应熔敷法,在钽合金表面制备一层较厚的碳化物强化层,进行钽合金的表面强化.以TaW12合金板材作为基板,将Ta粉和C粉混合,均匀涂覆在TaW12合金板材表面.以电弧为熔敷热源,在整个粉末涂覆面上进行逐行扫描,引发混合粉末与基板的反应熔融和固相扩散,获得表面硬化层.表面熔敷层完全致密,为熔融结晶状态.外表面呈周期性的波浪形,无裂纹,无气孔显现.熔敷层主要是Ta2C相与钽固溶体混合的共晶凝固组织,等轴状和条状的Ta2C相分布在Ta合金基体上,呈现一定的方向性,大多数近似垂直于板面.熔敷层与基体之间有一层由固态扩散产生的组织,大量针状Ta2C相在基体上交叉析出,形成网状结构.Ta2C相尺寸由外向内变小,逐步成为细小点状析出.熔敷层与过渡层间为固液界面,结合非常好,无裂纹和空洞存在.表面熔敷层平均维氏硬度为6690 MPa,达到了基体材料硬度的3倍.过渡层中硬度急剧下降,为熔敷层的一半.     

电接触烧结增强NiCr-Cr3C2涂层的显微组织和摩擦磨损行为研究

目的在等离子喷涂的基础上,采用电接触烧结技术制备具有良好摩擦学性能的Ni Cr-Cr_3C_2涂层。方法采用等离子喷涂工艺将NiCr-Cr_3C_2涂层预置到GH4169合金试件表面,再经过电接触烧结工艺制备增强涂层。利用OM、SEM、XRD及EDS研究耐磨层的物相、显微组织及化学组成特征,并采用球盘式摩擦磨损试验机对涂层的摩擦学行为进行评价。结果通过电接触烧结过程中的瞬时热效应,促进了NiCr-Cr_3C_2等离子喷涂层界面的塑性变形及热扩散,使涂层的孔隙率由5%降到2%,结合强度由46MPa提升到210 MPa。在400℃和600℃时,摩擦表面可形成完整的摩擦层,共晶氟化物组分使涂层摩擦系数由室温至400℃条件下的0.8降低到600℃条件下的0.45。涂层在600℃条件下表现出氧化磨损的特征。结论电接触烧结工艺能实现等离子喷涂Ni Cr-Cr_3C_2涂层的性能增强,获得较高结合强度、较低孔隙率和摩擦系数,在600℃条件下表现出较好的摩擦磨损性能。     

Plasma-Sprayed Hydroxyapatite Coating for Improved Corrosion Resistance and Bioactivity of Magnesium Alloy

In the present study, the corrosion resistance and bioactivity of AZ91HP magnesium alloy were improved by plasma spraying hydroxyapatite (HA) coating. X-ray diffraction measurements indicated that the coating formed amorphous and little β-Ca₃ (PO₄)₂ besides of HA. The corrosion resistance and bioactivity of the coating and magnesium alloy in simulated body fluid were investigated using immersion test. The coating showed lower corrosion rate and better bioactivity than magnesium alloy. The coating significantly improved the hydrophilicity of Mg alloy. The prothrombin time of the coating was 18 s, and the prothrombin time of Mg alloy was 11 s, so the coating had better anticoagulant activity.     

Fabrication and Characterization of Suspension Plasma-Sprayed Fluoridated Hydroxyapatite Coatings for Biomedical Applications

Fluoridated hydroxyapatite (FHA) coatings were prepared on a Ti substrate using a suspension plasma spraying technique. The crystalline phases and chemical compositions of the coatings were characterized using x-ray diffraction, Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy. The analysis confirmed that the coating consisted of an FHA phase. The corrosion behavior in simulated body fluid was studied using potentiodynamic polarization tests, and the results indicated that the FHA coating greatly enhanced the corrosion resistance of the Ti substrate. The chemical stability of the FHA coatings was assessed by evaluating the release of Ca²⁺ ions. The results indicated that the substitution of fluorine into the hydroxyapatite (HA) structure had a positive effect on the dissolution resistance of the HA. The antibacterial activity was investigated using a surface-plating method; the results revealed that the antibacterial activity of the FHA coating was greater than that of the pure HA coatings. During cell culture tests, the FHA coating did not exhibit cytotoxicity toward the osteoblast cell line, and the cell proliferation was comparable with that of the HA coatings. The antibacterial activity and cell culture results suggested that the plasma-sprayed FHA coating possesses good antibacterial qualities, but is biocompatible with osteoblasts. The promising features of the FHA coating render it suitable for orthopedic and dental applications.