YG8硬质颗粒增强镍基合金-WC复合涂层的组织与性能研究

采用火焰钎涂法在钢基体上制备了含不同YG8颗粒的镍基合金-WC复合涂层。采用SEM、EDS、HV和HRC等分析测试手段研究了涂层的组织与性能,探讨了YG8对涂层致密性和孔隙率的影响。结果表明,涂层组织中强化相和钎料基体相润湿良好,强化相WC颗粒和YG8颗粒均与钎料基体发生了相互扩散;适量的YG8明显降低了涂层的孔隙率、提高了涂层致密性,从而提高了涂层的硬度;当YG8含量为25%时,涂层组织中WC颗粒显微硬度达最大值,约1988.1HV0.1,钎料基体显微硬度也达最大值,为707.5HV0.1,同时涂层的宏观硬度值也达最大值,为48HRC。因此,在镍基合金-WC复合涂层中添加适量的YG8可明显提高涂层硬度,改善涂层耐磨性能。     

碳化硅/石墨复合陶瓷密封材料的显微结构与性能

以碳化硅微粉为原料、石墨为固体润滑添加剂,采用无压烧结技术制备碳化硅/石墨复合陶瓷密封材料,研究了石墨添加量对复合陶瓷密封材料烧结性能、显微结构、力学性能和摩擦性能的影响。结果表明,加入的石墨能以片状颗粒形态均匀分布在碳化硅陶瓷基体中;随着石墨添加量增加,复合陶瓷密封材料的体积密度、抗弯强度、弹性模量、断裂韧性、硬度均逐渐降低,但干、湿静摩擦系数则随之减小;当石墨添加量达到20%(质量分数)时,复合陶瓷的相对密度仅为90.6%,弯曲强度降至189 MPa,弹性模量降至295 GPa,断裂韧性为1.82 MPa·m1/2,Vickers硬度为19.2 GPa,而干、湿摩擦系数则分别减小到0.14和0.10。综合考虑复合陶瓷的力学性能和摩擦性能,石墨添加量控制在10%~15%之间为宜。     

TiAlSiN多层梯度涂层力学及摩擦磨损性能试验研究

利用物理气相沉积(PVD)技术,基于阴极电弧技术在Si片、高速钢试片上制备了TiAlSiN多层梯度涂层。利用洛氏硬度计、X射线衍射仪、透射电子显微镜、纳米压痕仪对涂层的表面形貌、物相结构和力学性能进行表征。通过超精密三维表面轮廓光学测量仪、HSR-2M摩擦磨损试验机测试涂层的摩擦磨损性能。试验结果表明TiAlSiN多层梯度涂层结构致密,各层间界面清晰,主要由柱状的面心立方结构的(Ti,Al)N相组成。涂层与基体的结合力达到工业等级HF1,具有良好的膜基结合力,其硬度为27.7 GPa,弹性模量为338.0 GPa,具有较高的硬度和弹性模量。TiAlSiN多层梯度涂层的摩擦系数为0.54,磨损率为7.06×10~3μm~3/(N·m),主要磨损机制为磨粒磨损和轻微粘着磨损。     

浮法玻璃在线镀复合膜的力学性能

用化学气相沉积法在浮法玻璃上制备了复合薄膜.用台阶仪、纳米压痕和X射线衍射分别测定了薄膜厚度、弹性模量、纳米硬度和室温时薄膜的残余应力.实验结果表明:薄膜厚度为560.7nm,弹性模量为48.33GPa,纳米硬度值为10.65GPa,计算得到薄膜的残余应力值为-0.19GPa.对膜厚、气体的配比、流量、玻璃板的厚度、玻璃基体的化学成分等因素对薄膜残余应力的影响进行了讨论.     

基于纳米力学的T300/PEEK复合材料各组分原位力学性能测试

采用纳米压痕和峰值力纳米力学模量成像技术(PF-QNM)对碳纤维/聚醚醚酮(T300/PEEK)复合材料各组分原位力学性能进行测试,并对复合材料界面结构及性能定量表征。结果表明,树脂基体、界面、碳纤维区域的弹性模量和硬度均呈梯度上升趋势,且纤维和树脂复合后的原位弹性模量与其非在位性能相比,分别下降和上升,说明高模量的纤维对周围树脂起到一定的强化作用。两种方法测得树脂基体平均弹性模量分别为5.4、4.1 GPa,测试结果分散度较小,与其宏观模量数值较为接近;研究显示,PF-QNM技术具有纳米级横向分辨率,测得T300/PEEK的界面厚度为(73.5±3.8)nm。     

莫来石涂层对氧化铝基体力学性能的影响

陶瓷材料的预应力增强已经被证明有效，但是这种表面预应力对其他力学性能的影响如何仍不明晰，本工作将探讨表面残余压应力对复合构件的综合力学性能的影响，包括弯曲强度、弹性模量、断裂韧性、硬度以及损伤容限。为了实现表层压应力以及相适配的界面剪切应力，按质量分数比1∶1将莫来石和氧化铝混合磨成浆料涂覆在预烧后的氧化铝基体上，经无压烧结后，涂层与基体紧密结合，随着温度下降，2种材料不同的收缩率和界面约束形成表层残余压应力，从而实现氧化铝复合陶瓷的预应力强化，进而测试了该材料的各项力学性能。结果表明：预应力涂层有效提高了基体材料的弯曲强度，提高了38.9%；断裂韧性提高了36.5%，弹性模量稍降、硬度下降代表了涂层材料的性能。通过这些力学参数，计算得到复合氧化铝陶瓷的损伤容限从0.389 4 m^1/2提升至0.452 7 m^1/2，提高了16.26%。     

水泥、磨细矿渣、粉煤灰颗粒弹性模量的比较

为了揭示磨细矿渣和粉煤灰对水泥基材料物理力学行为的影响机理,为应用计算机模拟掺有矿渣或粉煤灰的水泥基材料的物理力学行为提供必要的力学参数,应用纳米压痕技术实测水泥、磨细矿渣和粉煤灰颗粒的弹性模量。用酚醛树脂混合水泥、磨细矿渣或粉煤灰颗粒后再进行磨光、抛光和超声波清洗等工艺制得表面光洁度符合纳米硬度仪要求的试样。水泥、磨细矿渣及粉煤灰颗粒的弹性模量区间分别为[8．0GPa,33．6GPa],[5.7GPa,25.4GPa]和[17．9GPa,55．3GPa],其样本均值分别为17．4,12．8GPa和34．3GPa。     

连续刚度法对单晶硅片的力学性能的表征

利用纳米压痕仪通过连续刚度测量法对单晶硅片在压入过程中的接触刚度、硬度、弹性模量进行了连续测量.结果表明:当接触深度在20～32 nm左右时,单晶硅片的接触刚度与接触深度成直线关系,硬度和弹性模量基本保持不变,此时所测得的是单晶硅片表面氧化层的硬度和弹性模量,分别约为10.2 GPa和140.3 GPa.当接触深度在32～60 nm左右时,单晶硅片的接触刚度与接触深度成非直线关系,硬度和弹性模量随接触深度急剧增加,表明单晶硅片表面氧化层的硬度和弹性模量受到了基体材料的影响.当接触深度在60 nm以上时,单晶硅片的接触刚度与接触深度成直线关系,硬度和弹性模量基本保持不变,测得值为单晶硅的硬度和弹性模量,分别约为12.5 GPa和165.6 GPa.     

碳钢表面燃烧合成网络结构Cr_3C_2-WC陶瓷复合涂层的相组成与性能

利用燃烧合成技术,在普通碳钢表面原位自生Cr3C2-WC网络结构陶瓷复合涂层。通过X射线衍射仪、扫描电子显微镜、能谱仪和显微硬度计等测试手段对涂层中的网络结构陶瓷增强相的组织形貌、物相组成、化学成分及力学性能等进行了表征。结果表明:涂层由Cr3C2,WC,FeNi3,σ-FeCr和δ-CrNi等组成,Cr3C2-WC网络结构增强相由过饱和固溶体共晶析出。涂层与基体间的结合为冶金结合;表面涂层厚度约为2.0mm,显微硬度约为7.2GPa。制备的表面复合材料的硬度高于基体,改性效果明显。     

烧结温度对ZrO2薄膜表面形貌及力学性能的影响

采用溶胶-凝胶法在玻璃基体表面制备了经300℃,400℃和500℃烧结热处理的ZrO2薄膜.利用X射线衍射仪、原子力显微镜和纳米压痕仪研究了烧结温度对ZrO2薄膜表面形貌和力学性能的影响.实验结果表明,随着烧结温度的增加,ZrO2的晶体结构由少量的单斜晶相逐渐转变为单斜晶相和四方晶相的混合相.薄膜表面形貌逐渐改善,薄膜的表面粗糙度和颗粒度依次减小,薄膜的表面粗糙度分别为10.5 nm、7.2 nm和5.6 nm,ZrO2的粒径分别为188 nm、153 nm和130 nm.ZrO2薄膜的弹性模量和硬度都显著提高,薄膜的弹性模量分别为89.6 GPa、114.2 GPa和128.9 GPa,薄膜的硬度分别为7.6 GPa、10.3 GPa和15.1 GPa.     

Preparation of Strongly Adherent Platinum Coating by Double Glow Plasma Technology

Abstract

Strongly adherent Pt coating was deposited on Ti alloy substrates using double glow plasma technology. The polycrystalline Pt coating exhibited a preferred (220) orientation. The coating strongly adhered to the substrate, and the adhesive forces between the coating and substrate were all greater than 60 N. The hardness and elastic modulus of the coating were about 1.2 and 180 GPa, respectively. Adherent Pt coating had a better corrosion resistance than the bare substrate in terms of polarization curves. The bright Pt coating was still well bonded to the substrate after corrosion testing. This work suggested that strongly adherent Pt coatings on Ti alloy substrates can be used in industrial production processes.     

Synthesis of nanodiamond-reinforced aluminum metal matrix composites using cold-spray deposition

A dense nanodiamond–aluminum (ND–Al) composite coating was successfully produced by low pressure cold spray (CS) deposition of ball-milled powders containing 10 wt% ND. High-energy ball milling is a feasible means for the synthesis of composite feedstock powders as it provides excellent control over particle size distribution, crystal size, and the dispersion of ND agglomerates. The resulting CS coatings were characterized with respect to deposition efficiency, particle velocity and mechanical properties. It was found that the CS deposition produced dense, ND–Al composite coatings with increases in both hardness and elastic modulus as compared to the feedstock powders. The coating hardness of the 0.5 h-milled ND–Al composite that has the highest DE (14.2%) in ND–Al composites is 3.02 GPa, an 175% increase over the pristine as-received Al (1.10 GPa). The highest elastic modulus of the composite coatings is 98.3 GPa, a 51.5% increase over the as-received Al powder.     

纳米压痕技术对比研究DNAN和TNT晶体的微观力学性能

通过溶剂挥发法制备了DNAN和TNT晶体;利用纳米压痕技术研究了DNAN和TNT晶体的微观力学性能(硬度和弹性模量);通过原位扫描探针成像技术(SPM)研究了DNAN和TNT晶体的压痕形貌随时间的变化差异。结果表明,DNAN晶体的平均硬度和弹性模量分别为7.82GPa和0.22GPa,TNT晶体的平均硬度和弹性模量分别为12.19GPa和0.48GPa,表明TNT抵抗变形的能力优于DNAN;随着压痕深度由118nm增至856nm,DNAN的硬度从0.61GPa降至0.22GPa;随着压痕深度由27nm增至481nm,TNT的硬度从2.9GPa降至0.48GPa,表明DNAN和TNT均存在尺寸效应。随着时间由0增至50.4min,DNAN的压痕深度由-270.99nm减至-44.28nm,TNT的压痕深度由-415.12nm减至-369.21nm,表明DNAN晶体比TNT晶体具有更明显的慢回弹性,DNAN具有更强的冲击能量吸收能力。     

自组装ANFs/GO复合薄膜的结构与纳米压痕力学性能

将氧化石墨烯(GO)在氢氧化钾/二甲基亚砜中分散并与对位芳纶聚对苯二甲酰对苯二胺(PPTA)聚阴离子分散液混合得到稳定分散的复合分散液,将该复合分散液通过去离子水处理并利用自组装方法制备由直径为40 nm左右的高长径比芳纶纳米纤维(ANFs)和表面无羧基、羟基含量相对增多的部分脱氧GO(DGO)组成的复合薄膜。对系列复合薄膜进行电子显微镜观察和光谱学分析发现ANFs与DGO间通过氢键和π–π堆叠相互作用紧密结合形成多层结构。采用纳米压痕技术测试旋涂自组装方法制备的薄膜的微观力学性能,发现薄膜弹性模量和纳米硬度在GO用量为PPTA质量的1.5%时,分别达到了32 GPa和1.5 GPa,较未加GO的ANFs提升了104%和87.5%,表明ANFs与GO形成的DGO之间具有较强的协同增强作用。这种具有高硬度、高弹性模量的新型复合材料有望在个体防护、船壳材料、航空航天等领域发挥重要作用。     

Multiple cohesive cracking during nanoindentation in a hard W-C coating/steel substrate system by FEM

Stress evolution and subsequent cohesive cracking in the hard and stiff W-C coating on steel substrate during nanoindentation have been investigated using finite element modelling (FEM) and eXtended FEM (XFEM). The FEM simulations showed that the maximum principal stresses in the studied system were tensile and always located in the coating. They evolved in several stages. At indentation depths below 15% of the relative indentation depth, the maximum principal tensile stresses of ∼3 GPa developed at the top surface of the coating along the indenter/coating interface. At relative depths range 15–60%, the maximum tensile stresses of ∼6–8 GPa concentrated under the indenter tip in the coating along the interface with the substrate. At relative depths exceeding 60%, the maximum stresses gradually increased up to 10 GPa and they were located in the sink-in zone outside the indent as well as below the indenter tip. The first and subsequent cohesive cracks developed when the maximum tensile stresses in the sink-in zone at the top surface of the coating (and at the coating/substrate interface under the indenter) repeatedly reached the ultimate tensile strength of the coating. The hardness profile as well as cohesive cracking is controlled by the deformation of the substrate defined by the ration of the yield stresses of the coating and substrate. Very good correlation between the experimentally obtained cracks and multiple cracks predicted by XFEM confirmed the ability of the applied modelling in the prediction of fracture behavior of the studied coating/substrate system.     

Mechanical properties of MWPECVD diamond coatings on Si substrate via nanoindentation

The mechanical properties of polycrystalline diamond coatings with thickness varying from 0.92 to 44.65 μm have been analysed. The tested samples have been grown on silicon substrates via microwave plasma enhanced chemical vapour deposition from highly diluted gas mixtures CH₄-H₂ (1% CH₄ in H₂). Reliable hardness and elastic modulus values have been assessed on lightly polished surface of polycrystalline diamond films.The effect of the coating thickness on mechanical, morphological and chemical-structural properties is presented and discussed. In particular, the hardness increases from a value of about 52 to 95 GPa and the elastic modulus from 438 to 768 GPa by varying the coating thickness from 0.92 to 4.85 μm, while the values closer to those of natural diamond (H = 103 GPa and E = 1200 GPa) are reached for thicker films (> 5 μm). Additionally, the different thickness of the diamond coatings permits to select the significance of results and to highlight when the soft silicon substrate may affect the measured mechanical data. Thus, the nanoindentation experiments were made within the range from 0.65% to 10% of the film thickness by varying the maximum load from 3 to 80 mN.     

Carbon depth profile and internal stress by thermal energy variation in carbon-doped TiZrN coating

Diffusion and bonding behavior of the doped carbon by variation of thermal energy was investigated in terms of carbon depth profile and local atomic structure. The thermal energy of pulsed laser was limited to the range of 20%~50% to dope the carbon and prevent degradation of the coating layer with laser carburization. The doped carbon was confirmed to be distributed to a depth of around 20 nm from the surface at 20% thermal energy by ToF-SIMS analysis. Carbon diffused at about 400 nm with 50% thermal energy, and most of the carbon spread from the surface to around 80 nm. The EXAFS analysis represented that the peak of the interstitial carbon site was formed at 20% and the ZrN peak shifted toward the ZrC peak by increasing the thermal energy. The analysis of the electronic structure and the bonding state demonstrated that the proportion of substitutional carbon was about 21% at a thermal energy of 50%. The internal stress was calculated using HR-XRD with a 5-axes sample stage, which was −453 MPa before doping and then increased to −1494 MPa at 50% because the mixture of interstitial and substitutional carbon increased distortion inside the coating layer. The elastic modulus and hardness were 459 and 37.9 GPa at 50%, respectively, which were improved by 10% and 20% compared to those of the TiZrN coating.