Effect of nano-vanadium nitride on microstructure and properties of sintered Fe-Cu-based diamond composites

With FeCu₃₀ pre-alloy powder as the main component of the bond, a new type of nano‑vanadium nitride (VN) additive with different concentrations was introduced into Fe-Cu-based diamond composites to investigate the effect of nano-VN on the microstructure and properties of Fe-Cu-based diamond composites. The hardness, relative density, bending strength and wear loss weight of the fabricated specimens were tested, and then the fracture surfaces and worn surfaces of those specimens were analyzed using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results show that the Fe-Cu-based diamond composites with nano-VN addition exhibited an improvement in the mechanical properties, plasticity and wear resistance, which can be attributed to the dispersion strengthening and grain refinement caused by nano-VN. And the nano-VN can also activate sintering, which can significantly improve the wettability of the binder to diamonds, resulting in more binder elements wetting and diffusion on the diamond surface during the sintering process. Besides, the diamond composites showed the best properties with the addition of 2% nano-VN. That is, the bending strength and the HRB hardness of the diamond composites increased by 25% and 20%, respectively, and the wear resistance of the matrix and holding force coefficient of the matrix to diamond were improved significantly. But an excessive amount of nano-VN was detrimental to the mechanical properties of Fe-Cu-based diamond composites.     

Microstructure and wear performance of Al5083/CeO2/SiC mono and hybrid surface composites fabricated by friction stir processing

Friction stir processing (FSP) was utilized to produce surface composites by incorporating nano-sized cerium oxide (CeO₂) and silicon carbide (SiC) particles individually and in combined form into the Al5083 alloy matrix. The study signified the role of these reinforcements on microstructure and wear behavior of the resultant surface composite layers. The wear characteristics of the resultant mono and hybrid surface composite layers were investigated using a pin-on-disc wear tester at room temperature. The microstructural observations of FSPed regions and the worn out surfaces were performed by optical and scanning electron microscopy. Considerable grain refinement and uniform distribution of reinforcement particles were achieved inside the nugget zone. All the composite samples showed higher hardness and wear resistance compared to the base metal. Among the composite samples, the hybrid composite (Al5083/CeO₂/SiC) revealed the highest wear resistance and the lowest friction coefficient, whereas the Al5083/SiC composite exhibited the highest hardness, i.e., 1.5 times as hard as that of the Al5083 base metal. The enhancement in wear behavior of the hybrid composites was attributed to the solid lubrication effect provided by CeO₂ particles. The predominant wear mechanism was identified as severe adhesive in non-composite samples, which changed to abrasive wear and delamination in the presence of reinforcing particles.     

Interfacial structures and mechanical properties of a high entropy alloy-diamond composite

A FeCoCrNiMo high-entropy alloy (HEA)/diamond composite prepared by spark plasma sintering (SPS) was investigated. Sintering the HEA/diamond composites at different temperatures leads to different interfacial structures, which have an impact on the mechanical properties. The multiple microstructures at HEA/diamond interface have different effects on the retention of the HEA matrix on diamond particles. It was found that the interstitial strengthening effect, amorphous carbon and nano-scale ordered carbon complex were beneficial to the mechanical properties. Due to the good interfacial bonding strength between the HEA matrix and un-failed diamond particles, the composite sintered at 950 °C exhibited an optimized combination of mechanical properties, with a hardness of 630 HV, transverse rupture strength of 1310 MPa, and optimal wear resistance. The failure of the diamond particles and the formation of brittle chromium carbides at sintering temperature at 1000 °C can deteriorate the properties of HEA/diamond composites.     

CeO2掺杂对ZrO2-Y2O3纳米涂层性能的影响

在45钢基体表面等离子弧喷涂制备了掺杂不同含量CeO2纳米ZrO2涂层,运用XRD,SEM对涂层的组织结构进行了分析,测试了涂层的结合强度和显微硬度,考察了涂层与铝青铜对磨时的摩擦磨损性能．结果表明,CeO2增加了ZrO2涂层的致密性、结合强度和显微硬度．纳米ZrO2涂层中加入CeO2后,增加了ZrO2涂层／铝青铜摩擦副的摩擦系数,增强了纳米ZrO2涂层,耐磨能力．涂层与铝青铜对磨时,随着CeO2含量的增加,ZrO2涂层粘着磨损形式增强,而涂层脆性断裂脱落的趋势减轻．     

碳黑含量对放电等离子烧结Fe-Cr-C/TiCN复合材料组织和耐磨性的影响

采用机械合金化和放电等离子烧结法制备了不同碳含量的Fe-Cr-C/TiCN复合材料。通过扫描电镜、X射线衍射、维氏硬度和球-盘式摩擦试验,系统地研究了碳含量对Fe-Cr-C/TiCN复合材料组织和磨损性能的影响。结果表明,在含碳量为1.0%~5.0%（质量分数,下同）的烧结样品中形成了(Cr, Fe)₇C₃碳化物,而当碳含量达到4.0%~5.0%时,出现了(Cr, Fe)₃C相。碳含量对Fe-Cr-C/TiCN复合材料的组织均匀性和致密化有着较为重要的影响,当烧结温度为~1000 ℃时,致密度由未加碳时的95.0%提高到的99.7%（含碳量为3.0%）,说明已实现了完全致密化。当含碳量为3.0%时,维氏硬度达到11 940 MPa。此外,添加适量的碳（3.0%）有助于获得良好的磨损性能,即摩擦系数波动范围小,平均摩擦系数为0.320,磨损率为6.8×10^-4 mm³·N^-1·m^-1。     

Thermal and mechanical properties of ZrO2-CeO2 plasma-sprayed coatings

The thermal and mechanical properties of ZrC₂-C_{eO 2}plasma-sprayed coatings were evaluated to examine their potential as a thermal barrier coating. ZrO₂-CeO₂ solid-solution powders containing up to 70 mol % CeO₂ are successfully plasma sprayed, but cerium content decreases during spraying due to the vaporization of cerium oxide. Hardness is greatest at 30 mol% CeO₂. With increased CeO₂ content, the thermal conductivity decreases to 0.5 W/m K and the thermal expansion coefficient increases to 12.5 x 10_-6 /K. Increased torch input power causes both the relative density and the hardness to increase monotonically, while the thermal conductivity and the thermal expansion coefficient are not significantly affected. When heated above 1300 K, the coating shrinks considerably due to sintering and its thermal conductivity increases abruptly.     

Mechanical and Tribological Characterization of Al-Mg2Si Composites After Yttrium Addition and Heat Treatment

In this study, the effect of heat treatment and yttrium additions on the microstructure, mechanical properties, and tribological behavior of Al-15% Mg₂Si cast composites was investigated. The microstructural study revealed the presence of both primary and secondary Mg₂Si phases in all composite specimens and also Y-containing intermetallics (Al₂Y phases) at higher concentrations. It was also found that Y addition does not change the size and morphology of primary Mg₂Si particles considerably, but the pseudo-eutectic Mg₂Si changed from a flake-like morphology to fine fibrous or rod-like one. The results show that proper content of Y additions can reduce the amount of Mg₂Si phase through dissolving it into the matrix, lead to the precipitation of Al₂Y phase and improve the mechanical properties. Modified composites with 0.5% Y exhibited an ultimate tensile strength (UTS) of 290 MPa with an elongation of 4.3%. After exposing the composite to solution treatment at 520 °C for 4 h, the tensile strength of the composite continuously increased with the increase of Y content, and reached the maximum at 1% Y. The maximum UTS and elongation at room temperature for the heat-treated composites are 294 MPa and 7.4%, respectively. In the cast specimen, fracture surfaces are covered by packets with coarse steps, suggesting a brittle mode of failure. Modified composites with 0.5 wt.% Y contain several cracked particles together with a few decohered primary Mg₂Si particles. In solution heat-treated state, dimples present at the fracture surface are rather coarse but homogenous, showing a semi-ductile mode of fracture. Wear test results showed that the wear resistance of all specimens increases with the addition of Y up to 0.3 wt.%. Scanning electron microscopic observations of the worn surfaces revealed that the dominant wear mechanism was abrasive wear accompanied by some delamination wear mode.     

Superior Tribological Properties of Particulate Aluminum Matrix Nano Composites

Aluminum is the best metal for producing metal matrix composites which are known as one of the most useful and high-tech composites in our world. Combining aluminum and nano Al₂O₃ particles will yield a material with high mechanical properties. Characterization of tribological properties revealed that the presence of nano particles significantly increased wear resistance of the composite. In case of unreinforced Al alloy, the depth of penetration is governed by the hardness of the specimen surface and applied load. But, in case of Al matrix composite, the depth of penetration of the harder asperities of hardened steel disk is primarily governed by the protruded hard ceramic reinforcement. The hard Al₂O₃ particles act as a protrusion over the matrix, carries a major portion of the applied load and protect the abrasives from penetration into the specimen surface.     

激光原位合成TiB2-TiC颗粒增强铁基涂层

采用B4C,TiO2,石墨以及铁基粉末为激光熔覆材料,利用激光多道搭接熔覆技术在碳钢基体上制备TiB2-TiC颗粒增强铁基复合涂层．利用XRD,SEM对涂层的相结构和显微组织进行了研究．采用显微硬度计和滑动磨损试验机分别测试了涂层的硬度和耐磨性能．结果表明,激光熔覆过程B4C,TiO2和石墨反应生成了TiB2和TiC颗粒,并均匀分布在基体中．随着激光功率密度增加,涂层中TiC含量减少,甚至出现FeB脆性相．TiB2-TiC颗粒增强的涂层其硬度和耐磨性能优于基材45钢．     

Property improvement of stainless-steel-base surface composites fabricated by high-energy electron-beam irradiation

This is a study on the fabrication of surface composites of SiC, TiC particulates, and AISI 304 substrate by high voltage electron beam irradiation. Using CaF₂ powders as flux, two kinds of surface composites were fabricated for a comparative analysis of the microstructural modification and mechanical properties. Through the employed process, the powders and substrate surface were melted and surface composite layers were successfully formed in both cases. In the specimen fabricated with SiC powders, a volume fraction of Cr₂₃C₆ particles (−22 vol.%) were homogeneously distributed along solidification cell boundaries. The large amount of Cr₂₃C₆ particles in combination with solid solution hardening of Si in the matrix resulted in the improved hardness and wear resistance of the surface composite layer, that are 2 to 3 times those of the substrate. In the specimen fabricated with SiC and Ti+SiC powders, TiC and Cr₂₃C₆ particles were precipitated without precipitation of SiC.     

6061铝合金表面激光熔覆稀土CeO_2+Ni60组织及摩擦磨损性能

为提高铝合金的表面性能,利用激光熔覆技术在6061铝合金表面制备了添加稀土Ce O2的Ni60熔覆层,并通过金相显微镜、SEM、显微维氏硬度计和摩擦磨损试验机等设备研究了CeO2对Ni60熔覆层组织结构、硬度及摩擦磨损性能的影响.结果表明,加入2%的Ce O2可有效地减少熔覆层中的裂纹、孔洞和夹杂物,促进晶粒细化,提高熔覆层的组织均匀性、表面硬度及耐磨损性能;在相同磨粒磨损条件下,CeO2+Ni60熔覆层的耐磨性是铝合金的7.1倍,是Ni60熔覆层的1.6倍;Ni60熔覆层可以显著降低铝合金表面摩擦系数,而添加稀土CeO2能提高Ni60熔覆层的摩擦系数稳定性,从而改善Ce O2+Ni60熔覆层的耐磨性能.     

纳米Mg2Sn增强镁基复合材料组织与性能

利用纳米Sn粉高的表面活性,通过微米Mg粉与纳米Sn粉的机械合金化高效合成了含原位纳米Mg₂Sn相的复合粉末,将所得复合粉末热压烧结,获得高性能纳米Mg₂Sn增强镁基复合材料。对比研究了不同机械合金化时间对镁基复合材料组织、性能的影响,结果表明：随着机械合金化时间的延长,由纳米Mg₂Sn相组成的团簇尺寸不断减小,分布更加均匀,烧结态Mg₂Sn/Mg复合材料的各项力学性能也得到不断提高。     

添加CeO_2对MoS_2基复合涂层摩擦学性能的影响

针对MoS_2基复合涂层耐磨性差和承载能力低的问题,以不同含量(质量分数)的CeO_2作为添加剂,采用喷涂法在GCr15钢表面制备MoS_2基复合涂层。利用摩擦磨损试验机和划痕仪分别研究涂层摩擦磨损性能和结合强度,并借助金相显微镜对涂层磨损形貌进行表征。结果表明:添加适量CeO_2可以改善涂层的摩擦磨损性能,其最佳含量为2%,此时摩擦因数和磨损量均最小,分别为0.232和0.011 3 mm~3;同时结合强度从22 N提高到28.29 N。涂层磨损量随载荷的增大而增大;而载荷小于8 N时,涂层的摩擦因数随载荷的增大而减小,当载荷大于8 N时,摩擦因数又有回升趋势。添加稀土后涂层的承载能力有明显提高。未添加稀土时,涂层产生严重剥离,并发生磨粒磨损;添加2%CeO_2后,涂层发生轻微磨粒磨损,耐磨性得到显著提高。     

Corrosion protection properties of cerium layers formed on tinplate

Corrosion protection properties of cerium-passivated, unpassivated and chromium-passivated tinplates in contact with a 0.1 M citric-citrate buffer solution were studied using polarisation (DC) and electrochemical impedance spectroscopy (EIS) methods. The morphology and composition of the passive layer were studied using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS) in conjunction with argon-ion sputtering. Cerium-passivated tinplate showed similar corrosion properties to chromium-passivated tinplate in DC measurements, while the latter yielded the best corrosion resistance results in EIS measurements. SEM and EDX illustrated spherical particles with iron, cerium and tin contributions. XPS measurements indicated that the cerium-rich coating was a hydrated oxide with a composition of cerium(III): Ce(OH)₃ and cerium(IV): CeO₂ and Ce(OH)₄.     

Effect of iron on the wetting,sintering ability,and the physical and mechanical properties of boron carbide composites: A review

Due to its favorable physical, mechanical and chemical properties, boron carbide (B₄C) is one of the most important ceramics used in various industries. After diamond and boron nitride with a cubical structure, this material is the third hardest substance known; and due to its low density, large cross-sectional surface area for neutron absorption, excellent chemical stability, and other desired properties, it is considered as a strategic material. The sintering of boron carbide ceramics is very difficult due to the existence of strong covalent bonds in pure boron carbide and its low self-diffusion, high resistance against grain boundary slipping, and low surface energy. For these reasons, many additives have been added to boron carbide, as sintering aids. These additives, in addition to facilitating the sintering of boron carbide, do not have an adverse effect on its properties, and they improve the characteristics of the resulting product. Iron is one of the additives that reduces the sintering temperature and improves the mechanical properties of boron carbide by producing a liquid phase and thus preventing the growth of B₄C particles. In this paper, the role of iron additive in the wetting, sintering ability, and the physical and mechanical properties of boron carbide composites has been investigated.     

Effect of Compaction Load and Sintering Temperature on Tribological and Mechanical Behavior of Ni/SiC/MoS<Subscript>2</Subscript> Composites

In the present investigation, the effects of compaction load and sintering temperature on the tribological and mechanical behavior of Ni/20%SiC/7%MoS₂ hybrid composites was studied. The density, compression strength, and hardness of the composites were evaluated and compared. The wear properties of the composites were evaluated for the test condition of 1 m/s speed and 10 N load using a pin-on-disk tribometer. The braking performance of the composites was evaluated in a subscale dynamometer for the 500 kJ energy condition. The microstructure and wear surface morphology of the composites were analyzed by stereo, optical, and scanning electron microscopes. From the results, the following important conclusions are drawn: (1) the compaction load of 1400 kN and sintering temperature of 900 °C are optimum to obtain the best combination of tribological and mechanical properties; (2) the properties such as density, compression strength, hardness, wear, and friction increase up to a critical sintering temperature, and then decrease later; (3) the composition and thickness of the interface reaction product phases (Ni₂Si, Ni₃Si, and graphite) play a key role in deciding the strength of Ni/SiC interface that consequently affects the mechanical and tribological properties of the composites; (4) the abrasive wear is found to be the main wear mechanism in the highly densified composites, whereas the delamination wear and the third-body wear are major wear mechanisms in the poorly densified composites; and (5) the better braking performance of the highly densified composites is attributed to the absence of third-body wear, controlled flow of solid lubricant, and lower porosity.     

Ti-coated SiC particle reinforced sintered Fe-Cu-Sn alloy

Ti-coated SiC particles were developed to improve the wear resistance of Fe-Cu-Sn alloy metal matrices designed for diamond tools. The phase structure of the Ti-coated SiC particles was investigated by X-ray diffraction. Ti coating on SiC was composed of Ti₅Si₃, TiC, and Ti. Excellent interfacial bonding between SiC and the matrix was realized. The SiC/iron alloy composites, prepared by hot pressing at 820 °C, were studied by wear and bending strength tests, and scanning electron microscope. For the composites reinforced by uncoated SiC particles, the wear resistance was improved, but the bending strength decreased. The composites with Ti-coated SiC particles outperformed the composites with uncoated SiC particles in both wear resistance and bending strength tests.     

Tribocorrosion Behavior of Fe-Based Amorphous Composite Coating Reinforced by Al<Subscript>2</Subscript>O<Subscript>3</Subscript> in 3.5% NaCl Solution

Although corrosion and friction/wear behavior of Fe-based amorphous coatings and their composites has been extensively studied during the past decade, there is very limited work related to tribocorrosion behavior. In this paper, the tribocorrosion behavior of a Fe-based amorphous composite coating reinforced with 20 wt.% Al₂O₃ particles was investigated in a 3.5% NaCl solution on a ball-on-disk tester and was compared to the monolithic amorphous coating and 316L stainless steel (SS). The results showed that the amorphous composite coating exhibited the highest tribocorrosion resistance among the three materials tested, as evidenced by the lowest coefficient of friction (~0.3) and tribocorrosion wear rate (~1.2 × 10^?5 mm³/N·m). In addition, potentiodynamic polarization measurements before and during tribocorrosion testing demonstrated that corrosion resistance of the amorphous composite coating was not influenced so much by mechanical loading compared to the amorphous coating and the 316L SS. Observations on the worn surface revealed a corrosion-wear- and oxidational-wear-dominated tribocorrosion mechanism for the composite coatings. The excellent tribocorrosion resistance of the composite coating results from the effect of chemically stable Al₂O₃ phase which resists oxidation and delamination during sliding, along with poor wettability with corrosive NaCl droplets.     

Sintering and sliding wear studies of B4C-SiC composites

Dense boron carbide (B₄C) – silicon carbide (SiC) composites were obtained by spark plasma sintering technique at 1800°C with 3 wt% and 6 wt% aluminium oxide (Al₂O₃) additives. Addition of sintering additives results in formation of aluminium silicate (Al₂SiO₅) liquid phase which accelerates sintering kinetics and helps in obtaining high density ~ 99%. Microstructures reveal uniformly distributed SiC particles in B₄C matrix. Increase in alumina from 3 wt% to 6 wt% results in decrease in hardness from 35.1 ± 0.8 to 33.7 ± 0.9 GPa, and increase in fracture toughness from 5.9 ± 0.4 to 6.5 ± 0.4 MPam^0.5. Using a ball-on-disk tribo tester under dry unlubricated conditions at 5, 10 or 15 N load, influence of alumina content on friction and wear properties of B₄C-SiC composites was investigated against SiC counterbody with a linear speed of 0.08 m/s for 60 min. The coefficient of friction (COF) increased from 0.25 to 0.65 with load, and the influence of alumina on frictional behaviour appeared to be negligible. With increase in load, wear volume of the composites increased from 7.5 × 10⁻² mm³ to 16.1 × 10⁻² mm³ for B₄C-10 wt% SiC - 3 wt% Al₂O₃ and from 4.7 × 10⁻² mm³ to 14.8 × 10⁻² mm³ for B₄C-10 wt% SiC - 6 wt% Al₂O₃ composites. Microcracking, abrasion and pull-outs contributed as major wear mechanisms of composites in selected wear conditions. The relation between wear behaviour and mechanical properties of sintered composites is discussed.     

Wear Performance of A356 Matrix Composites Reinforced with Different Types of Reinforcing Particles

To improve the wear resistance of Al-Si alloys, different types of reinforcing particles such as SiC, TiC, ZrO₂, and B₄C were used to produce matrix composites by friction stir processing (FSP). First, microstructural properties of different locations of stir zone (SZ) in the FSPed specimens such as advancing side, retreating side, shoulder-affected area, and pin-affected area were investigated. The results demonstrate that Si particles size is not the same in different SZ subdomains. SEM investigation was performed in order to investigate the particles distribution in different areas of the SZ as well as bonding quality between particles and metal matrix. Hardness and wear tests were carried out to determine mechanical and wear properties of the composites. The pin-on-disk wear tests were performed at room temperature, with the normal applied loads of 5, 10, and 20 N and sliding speed of 1 and 2 m/s. All fabricated composites show higher resistance in wear than A356 alloy. Wear test results show, by increasing the normal load and sliding velocity, the wear loss weight of all composites increased gradually.