Papers by Keyword: Bonding Strength

Abstract: This article aims to improve the bonding strength between metal and plastic,the metal substrate is subjected to high-energy shot peening to make the surface self-nitrified, and the orthogonal test scheme was designed based on the process parameters of high energy shot peening and spraying. After molding, the bonding strength of the metal matrix composite was tested by the vertical stretching method. We studied the effect of the cast steel shot diameter, the shot peening pressure, the shot peening time and the plasticizing temperature on the bonding strength of the composite. The combination of process parameters was determined when the bonding strength was optimized, then use the numerical fitting method to predict the combination of process parameters when the bonding strength is the highest, the optimization results are verified by experiments. The results show that the diameter of the cast steel shot is 4.96mm-5.04mm, the shot peening pressure is 0.49MPa-0.51MPa, the shot peening time is 10.9min-11.08min, and the plasticizing temperature is 278.2°C-282°C. The bonding strength of the composite is optimal Keywords: Metal matrix composite, High-energy shot peening, Press forming; Bonding strength, Process optimization

Abstract: Understanding thermos-physical properties of MMCs includes considering interfacial processes and interactions between the constituents in MMCs. In this context, interfacial bonding is of vital interest for a deeper understanding of composites. Neutron diffraction experiments on Al/diamond composites were performed and reconciled with their thermo-physical properties and quantification of interfacial carbides formation. To create different interfacial conditions both, the contact time during processing the MMCs by liquid metal infiltration and the nominal composition of the matrix were changed, thus creating different amounts of interfacial Al₄C₃ carbides. Neutron diffraction showed the increase in contact time and the addition of Si to Al both increase the bonding strength, although going with a significant decrease of the composite`s thermal conductivity.

Abstract: The fabrication of porous diamond preforms is a key step for obtain diamond/metal copposites with high proporties by liquid infiltration. In order to prepare porous diamond preforms with high strength and excellent compatibility with liquid metal. The diamond metallization should be treated first usually.In this paper, the microstructure, composition, phase structure and bond strength of tungsten coating on diamond surface by using salt-bath method were observed and analyzed experimentally including scanning electron microscope (SEM), energy spectrometer analysis (EDS), X-ray diffraction (XRD). The results show that tungsten start to react with carbon atoms on the surface of diamond at 1100°C while a dense and completely covered coating can be obtained at the temperature of 1150°C with 10-120 minutes dwell time. With this process, the layer on diamond surface can be regulated in the range of 1.18 to 3.24μm. The phase structure of coating from outside to inside is W, W₂C and WC phase, respectively. Thermal shock experiments also show that the coatings on diamond surface have excellent bond strength as well as high temperature resistance.

Abstract: In this study the Ni-Al₂O₃-Zn coating was prepared on the surface of Q345R steel by cold spraying technique. The gas temperature, the content of Zn and the thickness of the coating were changed during spraying. The relationship between coating bond strength and three variables were studied. The results show that the bonding strength is the highest when the temperature is 400°C, the Zn content is 20% and the coating thickness is 0.5mm. It is found that the addition of Zn can significantly improve the bonding strength of the coating.

Abstract: The thermal barrier coating samples of different thickness with alumina coated zirconia and zirconia as coating materials were prepared on the surface of heat resistant alloy steel substrate after activation treatment with NiCoCrAlY as adhesive transition layer by plasma spraying method and spray gun quick spraying process. The bonding strength and thermal insulation property of two kinds of ceramic coating with the same thickness were compared by the test results of bonding strength, high temperature heat insulation and microstructure, and the relationship between the coating thickness and heat insulation effect were investigated. The results indicate that the structure and property of thermal barrier coating using nanoAl₂O₃ coated ZrO₂-Y₂O₃ powder are superior to that using single zirconia powder. The thermal insulation property of the thermal barrier coating increased with the increasing of coating thickness, and the advantage is more obvious with temperature increasing.

Abstract: Brake pad is the combination of lining and metallic components, e.g. steel backing plate (disc brake) and aluminum brake shoe (drum brake). Shear bond strength plays a major role to provide the safety and/or drive performances. This work aimed to study the processing factors affected the bonding strength. The molding temperature couple with post-curing temperature was simultaneously analyzed in order to optimize the processing temperature. The shear bond strengths of metallic plates were continually investigated with regard to the effect of different surface treatments. The obtained results indicated that the mechanical strength was increased as the molding temperature raised in ranges of 160°C to 180°C. Conversely, the deterioration of adhesive strength was progressively presented with rising post curing temperature. In comparing different backing plate, aluminum showed the higher shear bond strength than that of steel plate. In fact, the weakened property of aluminum in nature would be easily destroyed by mechanical treatments. From the shear tested results, an increase of surface roughness was inversely changed the shear bond strength. On the other hand, the contact angle of water droplet affected directly to adhesive strength. It was suggested that an adding surface roughness, commonly used in automotive industry, was inappropriate criteria, whist geometrical surface should be taken into account for improving the shear bond strength. Moreover, the contact angle and mechanical interlocking were recommended to use as a criteria of brake pad shear strength.

Abstract: Nickel based superalloy materials have being extensively used in aerospace and other high tech industries. In the present work, the effect of different substrates on the mechanical properties of the coating-substrate interface has been studied. To this end, alloy 718, commercially known as Inconel 718, was deposited on alloy 718 and low carbon steel substrates using High Velocity Oxygen Fuel (HVOF) technique at the same condition. The bonding strength of the interfaces evaluated using Vickers indentation test on the coating-substrate interface. Hardness results were subjected to a valid empirical method to estimate the fracture toughness. Results illustrated that using the same material as coating and the substrate led to stronger interface bonding strength due to higher hardness, fracture toughness, and less crack propagation.

Abstract: In this study, the effect of metal salt coating processing of aluminum surface on the bond strength of the solid-state diffusion bonded interface of titanium and aluminum has been investigated by SEM observation of the interfacial microstructures and fractured surfaces after tensile test. Aluminum surfaces were coated by boiling in 5% aqueous solution of NaOH for 90 s and 98% formic acid for 60 s. Bonding process was performed at a bonding temperature of 713 ~ 773 K under a load of 12 MPa (for a bonding time of 900 s). As a result of the metal salt coating processing, high strength joint can be achieved with lower bonding temperature compared with unmodified joints. From this study, it is found out that metal salt coating processing is effective at removing oxide film and substitution to metal salt on the aluminum bonding surface.

Abstract: Rock wool belt is one form of rock wool products used in external thermal insulation composite system. However, a related and important problem is how to improve bonding strength between rock wool belt and adhesive mortar. The present work studies the effect of interface agent on bonding strength. After interface agent was applied on the surface of rock wool belt, the original strength and water-resistance strength increased remarkably with the increasing of the concentration of interface agent, and the maximum value was almost 7 times over that without interface agent. It was believed that the significant increasing of bonding strength was related to fiber structure of rock wool belt, correspondingly, the interface agent could improve effective bonding area and increase the bonding depth. Moreover, it is worth noticing that the drying time of the interface agent had little effect on original strength and water-resistance strength, so it needn't a strict time requirement for rock wool bonding construction after applying interface agent.

Abstract: The comparison results of using crushed limestone (NA) and recycled concrete aggregates (RCA) as coarse aggregates in high-calcium fly ash geopolymer concrete with and without temperature curing are presented. Local river sand with a fineness modulus of 2.1, sodium hydroxide solution concentrations of 8, 12, and 16 Molar, and sodium silicate were used to produce geopolymer concrete (GC). The curing was separated in two conditions: the first was cured at ambient temperature (AT) and another was cured at temperature of 60°C for 48 hrs. (CT). The compressive strength, thermal conductivity, and ultra pulse velocity of GC were investigated at age 7 days. The results found that RCA could be use as coarse aggregate in GC. The thermal conductivity increased with the increasing of compressive strength. Curing at 60°C yielded compressive strength about 3 times higher than that of AT. However, both AT and CT curing, GC containing RCA had thermal conductivity and ultra pulse velocity lower than those of containing NA.