The effects of reactive gas partial pressure on droplet formation, deposition rate and change of preferred orientation of CrN and Cr2O3 coatings were studied. For CrN coatings, as nitrogen partial pressure increases, ...The effects of reactive gas partial pressure on droplet formation, deposition rate and change of preferred orientation of CrN and Cr2O3 coatings were studied. For CrN coatings, as nitrogen partial pressure increases, the number and size of droplets increases, the deposition rate initially increases obviously and then slowly, and the preferred orientation of CrN changes from high-index plane to low-index one. For Cr2O3 coatings, with the increase of oxygen partial pressure, the number and size of droplets decreases, the deposition rate decreases and the (300) becomes the preferred orientation. These differences are ascribed to the formation of CrN (with a lower melting point) and Cr2O3 (with a higher melting point) on the surface of Cr target during the deposition of CrN and Cr2O3. Complete coatings CrN or Cr2O3 film can be formed when reactive gas partial pressure gets up to 0.1 Pa. The optimized N2 partial pressure for CrN deposition is about 0.1?0.2 Pa in order to suppress the formation of droplets and the suitable O2 partial pressure for Cr2O3 deposition is approximately 0.1 Pa for the attempt to prevent the peel of the coating.展开更多
A study has been made of the cathodic polarization curves during the pulse plating of chromium from an aqueous chromic acid bath containing 250 g/L CrO3 and 2. 5 g/L H2SO4 at 22℃ over the range of pulse periods from ...A study has been made of the cathodic polarization curves during the pulse plating of chromium from an aqueous chromic acid bath containing 250 g/L CrO3 and 2. 5 g/L H2SO4 at 22℃ over the range of pulse periods from 1 ms to 50 ms. The duty cycle was kept at 50%. The methods of potentiostatic pulse potential control and galvanostatic pulse current control were used to determine the polarization curves of a platinum and a copper rotating disk electrode in the chromium plating solution. The results indicated that pulse potential and pulse current inhibited the formation of a cathode film and shifted the potential of the hydrogen evolution reaction toward the positive direction by about 500 mV. The potential and current pulses behaved as a depolarter of H+ reduction reaction. The present results agreed with a previous experimental observation that the coulombic efficiency of the chromium deposition reaction was reduced and the coulombic efficiency of the hydorgen evolution reaction was increased in pulse plating of chromium.展开更多
Thermal fatigue behavior of hard chromium electroplated steel in three different crack intensities of high contraction(HC), medium contraction (MC) and low contraction (LC) was studied. Maximum and minimum temperature...Thermal fatigue behavior of hard chromium electroplated steel in three different crack intensities of high contraction(HC), medium contraction (MC) and low contraction (LC) was studied. Maximum and minimum temperaturesduring thermal cycle were 800 and 100℃, respectively. The topography and cross sections of the samples exposedto 50, 100 and 200 thermal cycles were studied. The thermal fatigue behavior was analyzed using the data obtainedfrom surface roughness, crack networks and stress induced during cycles. Although the as-coated sample with LCchromium contained no crack, it appeared to have a high crack density after only 50 cycles. The crack depth andwidth in cyclically oxidized LC coating were much less than those in MC and HC coatings. It was concluded that theLC coating protected the substrate from having cracks or subsurface oxidation during thermal fatigue. The cracksin the HC and MC coatings increased in density as well as in depth by thermal cycles. Moreover, the opening of thecracks to the substrate resulted in sub-surface oxidation.展开更多
The growing demand for chromium coated aluminium components especially for the automotive industry is due to their favourable physical properties (density, strength to weight ratio etc.). However, their frequent use u...The growing demand for chromium coated aluminium components especially for the automotive industry is due to their favourable physical properties (density, strength to weight ratio etc.). However, their frequent use under harsh environmental conditions renders them corrosion sensitive and consequently they need to be protected. An approach that has been applied in industry is to directly electroplate nickel onto aluminium substrate prior to a top metallic finish;however, in components with complex geometry, certain areas could become exposed to corrosion attack due to poor surface coverage during plating. In this study, a modified electroless nickel undercoat was applied to pre-treated aluminium alloys prior to duplex nickel and chromium plating with a view to enhance corrosion resistance, improve coating adherence and durability, and overall, to achieve substrate protection. Hexavalent and trivalent chromium were applied to pre-treated Al 1050 and Al 6061 following electroless nickel deposition, and plating performance was assessed by surface and corrosion techniques, while durability was measured by scratch, adhesion and hardness tests. Overall, while chromium plating with an electroless nickel undercoat did not improve corrosion resistance or hardness of the materials, it provided an additional protective layer for the substrate with a potential for longer term durability.展开更多
Cr-Al-N ternary coatings were deposited by arc ion plating method using isolated Cr target and Al target. The influence of AlN content on the phase change was studied by synthesizing Cr1-xAlxN coatings with different ...Cr-Al-N ternary coatings were deposited by arc ion plating method using isolated Cr target and Al target. The influence of AlN content on the phase change was studied by synthesizing Cr1-xAlxN coatings with different x values. The effects of substrate negative bias on the surface morphology,deposition rate and phase structure were investigated. As the aluminum content increases,the structure of(Cr1-xAlx)N changes from B1(NaCl) phase to B4(wurtzite) phase. The critical content of AlN solubilized in B1(NaCl) lattice is close to 0.7. With the increasing pulse negative bias,the deposition rate decreases constantly,the droplet contamination is more serious,the ion-etching effect on coating surface is more obvious,and the change of preferred orientation and the shift of XRD peak take place.展开更多
Defibrator is a very important machine in the wood industry for producing fiberboard. The refiner plates are the key parts of defibrator that directly act with the wood, and broken easily. The working life of the refi...Defibrator is a very important machine in the wood industry for producing fiberboard. The refiner plates are the key parts of defibrator that directly act with the wood, and broken easily. The working life of the refiner plates is of significance to the wood industry. It may affect refining quality, production efficiency, and power consumption. In this paper, the abrasion resistance of the refiner plate made of different materials, the stainless steels and high chromium cast irons, were tested and compared. The results showed that abrasion resistance of refiner plate made of high chromium cast irons was better than that of the stainless steel materials. Although the two kinds of materials have the same compositions, their abrasion resistances have ap-parent difference. The main reason is that the material microstructures have very important effects on their performance. The refiner plates made of developed high chromium cast irons don抰 demand the complex heat treatment. This can simplify the producing process, save the cost of production, decrease labor strength, and increase the production efficiency.展开更多
The thermal emittance of Cr film, as an IR reflector, was investigated for the use in SSAC. The Cr thin films with different thicknesses were deposited on silicon wafers, optical quartz and stainless steel substrates ...The thermal emittance of Cr film, as an IR reflector, was investigated for the use in SSAC. The Cr thin films with different thicknesses were deposited on silicon wafers, optical quartz and stainless steel substrates by cathodic arc ion plating technology as a metallic IR reflector layer in SSAC. The thickness of Cr thin films was optimized to achieve the minimum thermal emittance. The effects of structural, microstructural, optical, surface and cross-sectional morphological properties of Cr thin films were investigated on the emittance. An optimal thickness about 450 nm of the Cr thin film for the lowest total thermal emittance of 0.05 was obtained. The experimental results suggested that the Cr metallic thin film with optimal thickness could be used as an effective infrared reflector for the development of SSAC structure.展开更多
This study developed a new technology for preparing high-chromium cast iron(HCCI)/low-carbon steel(LCS)wear-resistant composite plates by hot rolling at a 1050°C and a rolling speed of 0.2 m/s.The effects of diff...This study developed a new technology for preparing high-chromium cast iron(HCCI)/low-carbon steel(LCS)wear-resistant composite plates by hot rolling at a 1050°C and a rolling speed of 0.2 m/s.The effects of different rolling reductions(30%,45%,and 60%)on the microstructure(interface and HCCI layer)and mechanical properties(bonding strength,hardness,and wear resistance)of the composite plate were studied.SEM images showed that when the reduction was increased,no impurities and interlayers were found between the microscopic interfaces after hot rolling,and the bonding interface exhibited a wave-like shape.EDS analysis showed that the Cr element diffusion between two metals after hot rolling was promoted when the reduction was increased,thereby improving the bonding quality under the same rolling temperature and rolling speed.Experiments showed that due to the stress release effect of the LCS of the cladded layer,the macro-slab shape after hot rolling performed well,and the brittle HCCI layer underwent thermoplastic deformation without cracking.Moreover,the increase of rolling reduction improved the bonding quality.As the rolling reduction was increased,the volume fraction of Cr-carbides in the HCCI layer also increased,resulting in an increase of hardness and wear-resistance.展开更多
The surface treatment technology of hot aluminum-zinc steel plate and UV curing technology may be effectively combined in the present research. According to different light curing mechanisms, different formulations fr...The surface treatment technology of hot aluminum-zinc steel plate and UV curing technology may be effectively combined in the present research. According to different light curing mechanisms, different formulations from UV curing surface treatment agents can be applied to the surface treatment of hot aluminum-zinc steel plate, mainly including 3-ethyl-3-benzoxy-methyl oxacyclobutane (TCM 104) and 3,4-epoxy-cyclohexylformic acid -3',4'-epoxy-cyclohexyl methyl ester (UVR 6110) as active diluents, high molecular weight polyfunctional oxacyclobutane as oligomer, triaryl sulfonium salt as a cationic photoinitiator, and an anthracene compound as a sensitizer. 385 nm LED lamp used as a radiation resource, the effects of the proportion of active diluent, the type and amount of photoinitiator, the amount of sensitizer, the curing temperature, and the amount of nano-SiO<sub>2</sub> on the photocuring rate were investigated by photoper-scanning differential calorimetry (Photo-DSC). The experimental results show that the system has the fastest photocuring rate under the conditions of 8:2 ratio of TCM 104 to UVR 6110, 2.5% photoinitiator, 0.6% sensitizer, 0.2% nano-SiO<sub>2</sub> additive, and 80˚C curing temperature. Based on addition of the appropriate number of various additives, the cationic photocuring surface treatment solution was prepared and further coated on the hot-dip galvalume steel plates. After curing, the passivation films were characterized by neutral salt spray test (NSST), Fourier transform infrared spectroscopy (FT-IR), electrochemical testing and other methods. The results show that the formulations could be cured at an energy of 150 mJ/cm<sup>2</sup>, and the overall performance of the passivation film could meet with the requirements of the downstream users.展开更多
基金Projects (59971052 50401022) supported by the National Natural Science Foundation of China
文摘The effects of reactive gas partial pressure on droplet formation, deposition rate and change of preferred orientation of CrN and Cr2O3 coatings were studied. For CrN coatings, as nitrogen partial pressure increases, the number and size of droplets increases, the deposition rate initially increases obviously and then slowly, and the preferred orientation of CrN changes from high-index plane to low-index one. For Cr2O3 coatings, with the increase of oxygen partial pressure, the number and size of droplets decreases, the deposition rate decreases and the (300) becomes the preferred orientation. These differences are ascribed to the formation of CrN (with a lower melting point) and Cr2O3 (with a higher melting point) on the surface of Cr target during the deposition of CrN and Cr2O3. Complete coatings CrN or Cr2O3 film can be formed when reactive gas partial pressure gets up to 0.1 Pa. The optimized N2 partial pressure for CrN deposition is about 0.1?0.2 Pa in order to suppress the formation of droplets and the suitable O2 partial pressure for Cr2O3 deposition is approximately 0.1 Pa for the attempt to prevent the peel of the coating.
文摘A study has been made of the cathodic polarization curves during the pulse plating of chromium from an aqueous chromic acid bath containing 250 g/L CrO3 and 2. 5 g/L H2SO4 at 22℃ over the range of pulse periods from 1 ms to 50 ms. The duty cycle was kept at 50%. The methods of potentiostatic pulse potential control and galvanostatic pulse current control were used to determine the polarization curves of a platinum and a copper rotating disk electrode in the chromium plating solution. The results indicated that pulse potential and pulse current inhibited the formation of a cathode film and shifted the potential of the hydrogen evolution reaction toward the positive direction by about 500 mV. The potential and current pulses behaved as a depolarter of H+ reduction reaction. The present results agreed with a previous experimental observation that the coulombic efficiency of the chromium deposition reaction was reduced and the coulombic efficiency of the hydorgen evolution reaction was increased in pulse plating of chromium.
文摘Thermal fatigue behavior of hard chromium electroplated steel in three different crack intensities of high contraction(HC), medium contraction (MC) and low contraction (LC) was studied. Maximum and minimum temperaturesduring thermal cycle were 800 and 100℃, respectively. The topography and cross sections of the samples exposedto 50, 100 and 200 thermal cycles were studied. The thermal fatigue behavior was analyzed using the data obtainedfrom surface roughness, crack networks and stress induced during cycles. Although the as-coated sample with LCchromium contained no crack, it appeared to have a high crack density after only 50 cycles. The crack depth andwidth in cyclically oxidized LC coating were much less than those in MC and HC coatings. It was concluded that theLC coating protected the substrate from having cracks or subsurface oxidation during thermal fatigue. The cracksin the HC and MC coatings increased in density as well as in depth by thermal cycles. Moreover, the opening of thecracks to the substrate resulted in sub-surface oxidation.
文摘The growing demand for chromium coated aluminium components especially for the automotive industry is due to their favourable physical properties (density, strength to weight ratio etc.). However, their frequent use under harsh environmental conditions renders them corrosion sensitive and consequently they need to be protected. An approach that has been applied in industry is to directly electroplate nickel onto aluminium substrate prior to a top metallic finish;however, in components with complex geometry, certain areas could become exposed to corrosion attack due to poor surface coverage during plating. In this study, a modified electroless nickel undercoat was applied to pre-treated aluminium alloys prior to duplex nickel and chromium plating with a view to enhance corrosion resistance, improve coating adherence and durability, and overall, to achieve substrate protection. Hexavalent and trivalent chromium were applied to pre-treated Al 1050 and Al 6061 following electroless nickel deposition, and plating performance was assessed by surface and corrosion techniques, while durability was measured by scratch, adhesion and hardness tests. Overall, while chromium plating with an electroless nickel undercoat did not improve corrosion resistance or hardness of the materials, it provided an additional protective layer for the substrate with a potential for longer term durability.
基金Project(50401022) supported by the National Natural Science Foundation of ChinaProject(0650034) supported by the Natural Science Foundation of Jiangxi Province, China
文摘Cr-Al-N ternary coatings were deposited by arc ion plating method using isolated Cr target and Al target. The influence of AlN content on the phase change was studied by synthesizing Cr1-xAlxN coatings with different x values. The effects of substrate negative bias on the surface morphology,deposition rate and phase structure were investigated. As the aluminum content increases,the structure of(Cr1-xAlx)N changes from B1(NaCl) phase to B4(wurtzite) phase. The critical content of AlN solubilized in B1(NaCl) lattice is close to 0.7. With the increasing pulse negative bias,the deposition rate decreases constantly,the droplet contamination is more serious,the ion-etching effect on coating surface is more obvious,and the change of preferred orientation and the shift of XRD peak take place.
文摘Defibrator is a very important machine in the wood industry for producing fiberboard. The refiner plates are the key parts of defibrator that directly act with the wood, and broken easily. The working life of the refiner plates is of significance to the wood industry. It may affect refining quality, production efficiency, and power consumption. In this paper, the abrasion resistance of the refiner plate made of different materials, the stainless steels and high chromium cast irons, were tested and compared. The results showed that abrasion resistance of refiner plate made of high chromium cast irons was better than that of the stainless steel materials. Although the two kinds of materials have the same compositions, their abrasion resistances have ap-parent difference. The main reason is that the material microstructures have very important effects on their performance. The refiner plates made of developed high chromium cast irons don抰 demand the complex heat treatment. This can simplify the producing process, save the cost of production, decrease labor strength, and increase the production efficiency.
基金Funded by the National Natural Science Foundation of China(No.51402208)the Project by State Key Laboratory of Advanced Technology for Materials Synthesis and Processing(Wuhan University of Technology)(No.2016-KF-11)
文摘The thermal emittance of Cr film, as an IR reflector, was investigated for the use in SSAC. The Cr thin films with different thicknesses were deposited on silicon wafers, optical quartz and stainless steel substrates by cathodic arc ion plating technology as a metallic IR reflector layer in SSAC. The thickness of Cr thin films was optimized to achieve the minimum thermal emittance. The effects of structural, microstructural, optical, surface and cross-sectional morphological properties of Cr thin films were investigated on the emittance. An optimal thickness about 450 nm of the Cr thin film for the lowest total thermal emittance of 0.05 was obtained. The experimental results suggested that the Cr metallic thin film with optimal thickness could be used as an effective infrared reflector for the development of SSAC structure.
文摘This study developed a new technology for preparing high-chromium cast iron(HCCI)/low-carbon steel(LCS)wear-resistant composite plates by hot rolling at a 1050°C and a rolling speed of 0.2 m/s.The effects of different rolling reductions(30%,45%,and 60%)on the microstructure(interface and HCCI layer)and mechanical properties(bonding strength,hardness,and wear resistance)of the composite plate were studied.SEM images showed that when the reduction was increased,no impurities and interlayers were found between the microscopic interfaces after hot rolling,and the bonding interface exhibited a wave-like shape.EDS analysis showed that the Cr element diffusion between two metals after hot rolling was promoted when the reduction was increased,thereby improving the bonding quality under the same rolling temperature and rolling speed.Experiments showed that due to the stress release effect of the LCS of the cladded layer,the macro-slab shape after hot rolling performed well,and the brittle HCCI layer underwent thermoplastic deformation without cracking.Moreover,the increase of rolling reduction improved the bonding quality.As the rolling reduction was increased,the volume fraction of Cr-carbides in the HCCI layer also increased,resulting in an increase of hardness and wear-resistance.
文摘The surface treatment technology of hot aluminum-zinc steel plate and UV curing technology may be effectively combined in the present research. According to different light curing mechanisms, different formulations from UV curing surface treatment agents can be applied to the surface treatment of hot aluminum-zinc steel plate, mainly including 3-ethyl-3-benzoxy-methyl oxacyclobutane (TCM 104) and 3,4-epoxy-cyclohexylformic acid -3',4'-epoxy-cyclohexyl methyl ester (UVR 6110) as active diluents, high molecular weight polyfunctional oxacyclobutane as oligomer, triaryl sulfonium salt as a cationic photoinitiator, and an anthracene compound as a sensitizer. 385 nm LED lamp used as a radiation resource, the effects of the proportion of active diluent, the type and amount of photoinitiator, the amount of sensitizer, the curing temperature, and the amount of nano-SiO<sub>2</sub> on the photocuring rate were investigated by photoper-scanning differential calorimetry (Photo-DSC). The experimental results show that the system has the fastest photocuring rate under the conditions of 8:2 ratio of TCM 104 to UVR 6110, 2.5% photoinitiator, 0.6% sensitizer, 0.2% nano-SiO<sub>2</sub> additive, and 80˚C curing temperature. Based on addition of the appropriate number of various additives, the cationic photocuring surface treatment solution was prepared and further coated on the hot-dip galvalume steel plates. After curing, the passivation films were characterized by neutral salt spray test (NSST), Fourier transform infrared spectroscopy (FT-IR), electrochemical testing and other methods. The results show that the formulations could be cured at an energy of 150 mJ/cm<sup>2</sup>, and the overall performance of the passivation film could meet with the requirements of the downstream users.
