Hot Dipping Temperature Research Articles

Analysis of liquid–solid interface bonding behaviour of 7075 aluminium alloy/SiCp reinforced aluminium base alloy

The introduction of heterogeneous elements and the presence of the oxide layer on the surface of aluminum alloy usually play a negative role in the interfacial bonding of Al/Al bimetallic composites. To solve these two key problems of interfacial bonding of bimetallic composites. This work proposes to composite SiCp/7075(solid)-7075 alloy(liquid). The main alloying element Zn of 7075 alloy is selected to perform hot dip treatment on SiCp/7075(solid) to reduce the influence of the oxide layer on the surface of the aluminum alloy and the introduction of heterogeneous elements. Al/Al bimetallic composites were prepared by using a hot-dip/non-hot-dip zinc + liquid–solid composite casting process. The bimetallic composite interfacial bonding of SiCp/7075–7075 matrix alloy was studied. The results revealed that an oxide layer existed at the interface of the bimetallic composite upon preheating at 400–475 °C and hot dipping at 400–425 °C. With an increase in the hot-dip temperature, the interface oxide layer disappeared because of the combined effect of thermal expansion deformation, lower solidus temperature of the zinc-rich layer, and volume expansion of the solid–liquid phase transition. Metallurgically bonded interfaces were obtained at the hot-dip temperatures of 450 and 475 °C. The fracture location was on the SiCp/7075 Al matrix composite side, showing that this composite's interfacial bond strength was higher than that of the SiCp/7075 Al matrix composites. The results of this study provide a new idea for the preparation of lightweight wear-resistant Al/Al bimetallic composites by liquid-solid composite casting.

Effect of Annealing and Oxidation on the Microstructure Evolution of Hot-Dipped Aluminide Q345 Steel with Silicon Addition

Q345 steel was coated by hot dipping into molten pure aluminum and Al-Si baths. The coatings were annealed at 800 and 900 °C for 1–3 h and subsequently oxidized at 900 °C for 15 h in air. The results revealed that the thickness of the intermetallic layer increased with increasing hot-dipping time in the range of 700–750 °C, while it decreased when the hot-dipping aluminizing temperature was 800 °C. As the silicon content in the aluminum bath increased, the thickness of the intermetallic layer decreased, and the intermetallic layer/steel-substrate interface transformed from an irregular morphology into a flat morphology. The hot-dipped Al-2.5Si samples were subjected to annealing; the higher the annealing temperature and longer the annealing time, the faster the transformation of the intermediate phase in the coating. The Fe2Al5 phase was fully transformed into the ductile FeAl phase after the hot-dipped samples annealed at 900 °C for 3 h. When the outermost layer of Q345 steel was the FeAl phase, oxidation resistance of the oxide was the best.

Effects of hot dipping temperature on microstructure and mechanical properties of Pb40Sn60 alloy coating on copper wires

Abstract Hot dip plating was used to prepare Pb40Sn60 alloy coating on copper wires to improve weldability and corrosion resistance. The microstructure and phase composition of Pb40Sn60 alloy coatings at different hot dipping temperatures were examined by scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD), and the mechanical properties of copper wires after hot dip plated Pb40Sn60 alloy coatings at different temperatures were investigated by the tensile test and hardness test. The results showed that the microstructure of Pb40Sn60 alloy coatings consisted of primary α phase and (α+β) eutectic structure, the phase were composed of α phase and β phase, and β phase was more than α phase in relative amount. With increase of hot dipping temperature from 210 °C to 250 °C, the thickness of Pb40Sn60 alloy coating on copper wire was decreased from 39.4 mm to 20.5 mm, the proportion of α phase in relative amount increased from 33.2% to 40.5%, the crystal morphology of primary α phase changed from lamellar or equiaxial to dendritic, and (α+β) eutectic structure changed from small lamellar to granular. The work hardening of copper wires can be eliminated during hot dip plating. With increase of hot dipping temperature from 210 °C to 250 °C, the strength of copper wire after hot dip plated Pb40Sn60 alloy coating decreased from 234 MPa to 213 MPa, the elongation was not obvious change, and the hardness of copper wire substrate decreased from 87 HV0.2 to 69.9 HV0.2, the hardness of coating increased from 10.1 HV0.2 to 13.4 HV0.2. It has been found that increase in the hot dipping temperature was beneficial to eliminate work hardening of copper wire substrate, while resulted in decreasing in deformation resistance, and also the decrease of coating thickness. On the contrary, decrease in the hot dipping temperature was beneficial to increase thickness of Pb40Sn60 coating, but the effects of eliminating on work hardening of copper wire were weakened.

Microstructure and Mechanical Properties of MoSi2 Coating Deposited on Mo Substrate by Hot Dipping Processes

MoSi2 coating was deposited on Mo substrate by a hot dipping process within the silicon bath. The effects of the hot dipping temperature and time on the thickness and mechanical properties of MoSi2 coating have been investigated. The results indicated that the average hardness of MoSi2 coating is only 209.15 MPa, and the average flexural strength is 873.63 MPa. Therefore, the MoSi2 coating deposited on Mo substrate exhibit better mechanical properties than monolithic MoSi2 and MoSi2 -based composites. In addition, the hot dipping processes have an important influence on mechanical properties. The hardness and flexural strength decrease sharply with increasing hot dipping temperature, then increases slightly on increasing hot dipping temperature. Meanwhile, the hardness and flexural strength increase sharply with increasing hot-dipping time.

Effect of hot dip silicon-plating temperature on microstructure characteristics of silicide coating on tungsten substrate

W-silicide coatings were deposited on tungsten substrate by using hot dip silicon-plating method under various temperatures. The phase composition, microstructure, and concentration distribution of elements were investigated. The results show that the W-silicide coatings consist of WSi2 layer and interface layer (W5Si3 layer), and the WSi2 coatings have a strong preferred orientation on the (211) and (206) crystal faces. The hot dip temperature has a significant effect on thicknesses and grain sizes of coatings. With the increase of hot dip temperature, the thicknesses of WSi2 layer and W5Si3 layer, and grain sizes increase obviously. Moreover, a high silicon concentration is observed at coating surface when the temperature is 1560 °C, and the highest silicon concentration is about 46 wt% (84.79 at.%).

Characterization of interfaces in tri-layered brass/steel/brass composites fabricated by casting and hot dipping

AbstractTri-layered brass steel/brass laminated composites were fabricated through hot dipping as well as casting. The chosen temperatures for hot dipping were 1 150 °C and 1 350 °C and for casting was 1 150 °C in addition to performing a heat treatment cycle at 900 °C for 90 min. The characterization results revealed that in the as-cast and the heat-treated samples, the formation of Fe-Zn intermetallic compounds occurred. In addition, with increasing the hot dipping temperature, stronger interfaces were achieved due to easier diffusion at higher temperatures. Moreover, casting without heat treatment was enough to obtain good bonding since the amount of Fe3Zn10 intermetallic compound increased and grain growth occurred.

Influence of thermal treatment temperature on high-performance varistors prepared by hot-dipping tin oxide thin films in Nb2O5 powder

SnOx-Nb2O5 thin film varistors were prepared by hot-dipping oxygen-deficient tin oxide films in Nb2O5 powder in air, and the influence of hot-dipping temperature (HDT) on the varistor performance of the samples was systematically explored. When the HDT increased from 300 to 700 °C, the nonlinear coefficient of the samples raised first and then dropped down, reaching the maximum of 14.73 at 500 °C, and the breakdown electric field exhibited a similar variation trend, gaining the peak value of 0.0201 V/nm at this temperature. Correspondingly, the leakage current decreased first and then increased with increasing HDT, reaching the minimum of 17.1 mA/cm2 at 500 °C. Besides, it was proposed that a grain-boundary defect barrier model was responsible for the nonlinear behavior of the obtained SnOx-Nb2O5 film varistors. This high-performance thin film varistor with nanoscaled thickness might be much promising in nano-devices or devices working in low voltage.

Highly nonlinear varistors fabricated by hot-dipping tin oxide thin films in Ta2O5 powder at different temperatures

This work proposed a smart approach to fabricate highly nonlinear SnOx-Ta2O5 thin film varistors. During processing, tin oxide films in nanoscaled thickness were firstly deposited onto electrically conducting silicon wafers through radio frequency magnetron sputtering a sintered tin oxide ceramic target; and then, the obtained films were hot-dipped in Ta2O5 powder in a Muffle oven for 60min at different temperatures. With the hot-dipping temperature increased from 300 to 800°C, the nonlinear coefficient of the samples increased first and then decreased, reaching the maximum of 16.8 at 600°C, which is a record in all the reported SnO2-based varistors and comparable with those of the most extensively investigated and commonly commercially applied ZnO-based ceramic varistors. Correspondingly, the leakage current decreased first and then increased, obtaining the minimum of 4.1mA/cm2. Besides, the breakdown electric field increased first and then decreased, presenting the maximum of 0.0313V/nm. Such nanoscaled thin film varistors would be promising in electrical and electronic devices working in low-voltage.

High‐performance varistors prepared by hot‐dipping tin oxide thin films in Sb2O3 powder: Influence of temperature

AbstractA series of SnOx–Sb2O3 thin film varistors were fabricated through hot‐dipping tin oxide films deposited by radio‐frequency magnetron sputtering in Sb2O3 powder at varied temperatures in air. With the increase in hot‐dipping temperature (HDT) from 200°C to 600°C, the nonlinear coefficient (α) of the samples increased first and then decreased, reaching the maximum at 500°C, which was mainly determined by the completeness of high‐resistant Sb2O3 layer at tin oxide grain boundary and the chemical composition of tin oxide films. Correspondingly, the leakage current (IL) decreased first and increased later. The breakdown electric field (E100 mA) decreased constantly with increasing HDT. The SnOx–Sb2O3 film varistors prepared at 500°C exhibited the optimum nonlinear properties with the maximum α of 10.88, the minimum IL of 36.3 mA/cm2, and an E100mA of 0.0188 V/nm. The obtained nanoscaled film varistors would be promising in electrical/electronic devices working in low voltage.

High-performance varistors simply by hot-dipping zinc oxide thin films in Pr6O11: Influence of temperature

High-performance ZnO-Pr6O11 thin-film varistors were fabricated simply by hot-dipping oxygen-deficient zinc oxide thin films in Pr6O11 powder. The films had a composition of ZnO0.81 and a thickness of about 200 nm, which were deposited by radio frequency magnetron sputtering a sintered zinc oxide ceramic target. Special attention was paid on the temperature dependence of the varistors. In 50 min with hot-dipping temperature increased from 300–700 °C, the nonlinear coefficient (α) of the varistors increased, but with higher temperature it decreased again. Correspondingly, the leakage current (IL) decreased first and then increased, owing mainly to the formation and destroying of complete zinc oxide/Pr6O11 grain boundaries. The breakdown field (E1mA) decreased monotonously from 0.02217 to 0.01623 V/nm with increasing temperature (300–800 °C), due to the decreased number of effective grain boundaries in the varistors. The varistors prepared at 700 °C exhibited the optimum nonlinear properties with the highest α = 39.29, lowest IL = 0.02736 mA/cm2, and E1mA = 0.01757 V/nm. And after charge-discharge at room temperature for 1000 times, heating at 100 or 250 °C for up to 100 h, or applying at up to 250 °C, the varistors still performed well. Such nanoscaled thin-film varistors will be very promising in electrical/electronic devices working at low voltage.

Highly nonlinear varistors from oxygen-deficient zinc oxide thin films by hot-dipping in Bi2O3: Influence of temperature

Highly nonlinear varistors were fabricated by hot-dipping oxygen-deficient zinc oxide (ZnO1−x, x<1) thin films in Bi2O3. The ZnO1−x films were deposited on conducting silicon chips by radio frequency magnetron sputtering of a sintered zinc oxide ceramic target. Then the films were hot-dipped at a temperature from 200 to 600°C in Bi2O3. With the increase in hot-dipping temperature, the nonlinear coefficient (α) of the film varistors increases first and then decreases, and the leakage current (IL) correspondingly decreases initially and then increases, owing mainly to the formation and destroying of complete ZnO1−x/Bi2O3 grain boundaries and the roundness change of the ZnO1−x grains; and the varistor voltage (E1mA) decreases from 0.0268 to 0.0137V/nm, due to the decreased number of effective grain boundaries in the materials. The film varistors prepared by hot-dipping at 400°C exhibit the optimum nonlinear properties with the highest α=15.1, lowest IL=0.0223mA/cm2, and E1mA=0.0176V/nm. Such nanoscaled film varistors will be very promising in electrical/electronic devices working in low-voltage.

Research on Elements Distribution in Hot Dip Aluminum Silicon Coating of Hot Stamping Steel

Al-Si coating in different hot dip process conditions were made by a hot-dip galvanizing simulator, and distribution regularities of chemical elements in coating were studied by means of GDS, SEM, EDS and XRD. The results show that the hot dip temperature has no obvious impact on elements distribution in coating, but has some impact on Si content in surface coating. The hot dip time has no obvious impact on surface coating element content, but has distinct impact on deep coating element content. With the hot dip time increasing, Al content decreases, Fe content increases, and Si content decreases. Al-Si coating is composed of 3 layers, surface layer contains fine and close Al2O3 film, which has good anti-oxidation property on high temperature and hot stamping property, middle layer contains high melting point phase ,such as rich Fe phase , FeAl3 ,which has excellent anti-oxidation property on high temperature. The elements in diffusion layer can even be transited to basic steel, so coating has good adhesion property.

Properties and Growth Rate of Intermetallic Al-Fe through Hot Dipped Aluminizing

Hot dipped aluminizing is the one of the most famous and effective method of the surface protection. The growth behavior in the intermetallic layer by introducing a different dipping time and various of molten aluminium temperature had been detail investigated. The result showed that the top portion of the coated steel substrate is compose of a thin layer of α-Al2O3, followed by thicker Aluminium pure layer, thinner layer of FeAl3 , and then a much thicker of Fe2Al5. The inter-metallic layer is ‘thick’ and exhibits a finger-like growth into the steel. The thickness of Al-Fe intermetallic layer on the steel base is increased with the increasing of hot dipping temperature and time. The micro hardness testing result shown that increasing of the aluminizing temperature was increased the hardness of the intermetallic layer.

Study on the Factors Influencing Plating Coat Thickness in Ultrasonic-Aided Hot-Dip Aluminizing Facing Remanufacturing

An aluminum layer can be gotten on the worn-out work piece surface through ultrasonic-aided hot-dip and converted into alumina layer having wear-resistance performance though micro arc oxidation which can realize remanufacturing. The key technology of hot-dip aluminizing phase in above remanufacturing process is controlling the plating coat thickness. The influences of withdrawing speed, hot-dip temperature and hot-dip time on the plating coat thickness are analyzed in this paper.

Optimization of Process Parameters of Hot-Dip Aluminized Coating

The hot-dip aluminized process parameters with respect to the thickness and microstructure of intermetalic layer were investigated using a uniform design of experiments. The measured thickness of intermetalic layer was regressed as first- to third-order polynomial equations of four related parameters, i.e. hot-dip temperature, hot-dip time, diffusion treatment temperature and diffusion treatment time. It was found that the third-order regressed equation was acceptable and appropriate to identify the influences of the investigated parameters on the thickness of intermetalic layer. Comprehensive analysis of the results based on the regressed equation and microstructure could supply believable and optimized process parameters.

Investigation on colourisation regularity of colouring hot dip galvanisation processing

The colouring hot dip galvanisation is a new hot galvanising processing. In this processing, a colour oxide film would be developed directly on the coating of the galvanised steel by the preferential oxidation of the additions in the hot dip galvanisation coating after hot dip operation. Due to their oxygen potentials and their oxide film properties, manganese and titanium were selected as additional elements in the colouring hot dip bath respectively. The influences of processing parameters on the colouring of coating were investigated systematically for the various binary Zn–Mn or Zn–Ti hot galvanising baths. The experimental results indicate that the colours on the coating of the galvanised steel would change continuously during its cooling period after hot dip operation. In the case of Zn–Mn bath, the possible colour tones of the oxide film are blue, yellow, purple and green, and their colour tones and the duration time varied with the manganese percentage composition and the hot dip temperature. In the case of Zn–Ti bath, the possible colour tones of the oxide film are blue, yellow and purple. However, titanium percentage composition in Zn–Ti bath has hardly effect on colouration regularity.

Hot water dipping and low temperature storage of 'Eureka' lemons

Summary. Prestorage heat treatments at 47–53°C for 1–3 min were investigated as a potential control of chilling injury in cold disinfested ‘Eureka’ lemons (Citrus limon). Hot water dips significantly reduced the incidence of chilling injury in fruit stored at 1°C for 28 and 42 days. Storage at 1°C for 14 days resulted in comparatively minor chilling injury, so that hot water dips gave little additional benefit. This result is thought to reflect the low incidence of chilling injury, rather than the lack of effectiveness of heat treatments. Scald damage (surface browning) occurred after 3 min at 53°C. Heat treatments had no significant effect on the incidence of disease at all durations of storage. The rate of fruit weight loss during 7 days at 20°C after storage for 14, 28 or 42 days at 1°C was significantly lower in heat- treated fruit.

The effect of silicon in steel on the growth of intermetallic phases during hot dipping in a Zn-5% Al melt

The effect of silicon present in steel on the growth of intermetallic phases in a Galfan bath (5wt.% Al-Zn plus 0.05% mischmetal) has been studied. Steel specimens containing 1.6% Si were hot dopped at temperatures in the range 450 °C to 520 °C for times between 50 and 1560 s. At all temperatures silicon was found to reduce dramatically the growth of the intermetallic phases and this slow growth results in a planar intermetallic/substrate interface being formed. The intermetallic grows in layer form initially and then develops a layered breakaway morphology whose growth rate depends on hot dipping temperature. The breakaway layer was determined to be a phase isomorphous with FeAl 3 with the thin layer next to the substrate a phase isomorphous with Fe 2Al 5. The extremely slow growth of the phase isomorphous with Fe 2Al 5 is the determining factor for the overall slow growth of the intermetallic layers.