The powders of NiCrW and NiCrWRE alloys were flame sprayed on a medium-carbon steel substrate by thermal spray welding. The micro- structure and tribological behavior of coatings were studied experimentally by means o...The powders of NiCrW and NiCrWRE alloys were flame sprayed on a medium-carbon steel substrate by thermal spray welding. The micro- structure and tribological behavior of coatings were studied experimentally by means of scanning electron microscopy （SEM）, field emission gun scanning electron microscope （FEGSEM）, and wear tests. The addition of CeO2 modifies the coating morphology from a needle-like structure to a roughly cubic morphology; the refining and purifying effect of rare earth elements makes the microstmcture more compact and finer. Analysis of the worn surfaces reveals that the coatings with CeO2 addition show improved abrasive wear resistance over those without CeO2. By adding CeO2, the hardness of the coatings is significantly increased, and the wear resistance of the coatings is enhanced.展开更多
Yttrium silicate, for its high oxidation resistance, is an important candidate for protective coating for carbon-fiber-reinforced composites at temperatures above 1600 ℃. A novel method, consisting of coprecipitation...Yttrium silicate, for its high oxidation resistance, is an important candidate for protective coating for carbon-fiber-reinforced composites at temperatures above 1600 ℃. A novel method, consisting of coprecipitation, spray-drying, heat-treatment and plasma-densification, is developed to prepare Y2SiO5 powders for thermal-spraying. The composition, morphology and flowability of the synthesized Y2SiO5 powders are investigated by XRD, SEM and Hall Flowmeter, respectively. The results show that the synthesized Y2SiO5 powders are nearly spherical with high purity. The apparent density and flowability of the Y2SiO5 powders are 1.87 g/cm^3 and 37 s/50 g, respectively, which lead to a high deposition efficiency of up to 80700 for atmospheric plasma spraying.展开更多
Three different groups of ceramic powders for the thermal-swayed coating were firstly prepared using sintering and ball milling. Then, these powders were separately deposited on three stainless steel substrates, follo...Three different groups of ceramic powders for the thermal-swayed coating were firstly prepared using sintering and ball milling. Then, these powders were separately deposited on three stainless steel substrates, followed by individual corrosion resistance examination. Microstructural characterization showed that the levels of micro-void and micro-crack at the bonding interface （between coating and substrate） depended on the proportions of different ceramic particles. Meanwhile, a significantly enhanced corrosion resistance was reproducibly observed in one group of as-coated samples that have the optimal combination of given ceramic powders. Furthermore, the mechanism of corresponding enhanced corrosion resistance was discussed. It was found that the optimal ceramic powders for the present thermal-sprayed coating should contain 30.2 wt% SiO2, 54 wt% Cr2O3, 6.8 wt% Al2O3, 4.8 wt% CaO and 1.8 wt% TiO2. The corrosion velocities of such samples in the 3.5 vol.% HCl, 15 wt% NaOH and 5 wt% NaCl solutions were 3.74, 2.98 and 0.50 g h-1 m-2 for 168, 336 and 336 h, respectively.展开更多
The electrochemical performance of the anodes was measured in the reinforced concrete test block in artificial sea water. Their chemical composition,metallographic structure and surface morphology were analyzed. It wa...The electrochemical performance of the anodes was measured in the reinforced concrete test block in artificial sea water. Their chemical composition,metallographic structure and surface morphology were analyzed. It was found that concrete mix proportion and the covering layer thickness had an impact on the performance of sacrificial anodes. The thermal-sprayed zinc alloy anodes had a more negative corrosion potential and larger galvanic current than metallurgy ones in the same conditions. They had similar chemical composition. But metallographic structure showed that the structure of thermal-sprayed zinc alloy anodes was a loose porous. This structure had the catalytic effect on the andes electrochemical reactions and made the anodes the electrochemical exchange current density increase and the corrosion potential move to negative direction.展开更多
基金This study was financially supported by the Natural Science Foundation of Gansu Province,China(No.0710RJZA071).
文摘The powders of NiCrW and NiCrWRE alloys were flame sprayed on a medium-carbon steel substrate by thermal spray welding. The micro- structure and tribological behavior of coatings were studied experimentally by means of scanning electron microscopy （SEM）, field emission gun scanning electron microscope （FEGSEM）, and wear tests. The addition of CeO2 modifies the coating morphology from a needle-like structure to a roughly cubic morphology; the refining and purifying effect of rare earth elements makes the microstmcture more compact and finer. Analysis of the worn surfaces reveals that the coatings with CeO2 addition show improved abrasive wear resistance over those without CeO2. By adding CeO2, the hardness of the coatings is significantly increased, and the wear resistance of the coatings is enhanced.
基金supported by the National Fundamental Research Program (No. A1320070102)
文摘Yttrium silicate, for its high oxidation resistance, is an important candidate for protective coating for carbon-fiber-reinforced composites at temperatures above 1600 ℃. A novel method, consisting of coprecipitation, spray-drying, heat-treatment and plasma-densification, is developed to prepare Y2SiO5 powders for thermal-spraying. The composition, morphology and flowability of the synthesized Y2SiO5 powders are investigated by XRD, SEM and Hall Flowmeter, respectively. The results show that the synthesized Y2SiO5 powders are nearly spherical with high purity. The apparent density and flowability of the Y2SiO5 powders are 1.87 g/cm^3 and 37 s/50 g, respectively, which lead to a high deposition efficiency of up to 80700 for atmospheric plasma spraying.
文摘Three different groups of ceramic powders for the thermal-swayed coating were firstly prepared using sintering and ball milling. Then, these powders were separately deposited on three stainless steel substrates, followed by individual corrosion resistance examination. Microstructural characterization showed that the levels of micro-void and micro-crack at the bonding interface （between coating and substrate） depended on the proportions of different ceramic particles. Meanwhile, a significantly enhanced corrosion resistance was reproducibly observed in one group of as-coated samples that have the optimal combination of given ceramic powders. Furthermore, the mechanism of corresponding enhanced corrosion resistance was discussed. It was found that the optimal ceramic powders for the present thermal-sprayed coating should contain 30.2 wt% SiO2, 54 wt% Cr2O3, 6.8 wt% Al2O3, 4.8 wt% CaO and 1.8 wt% TiO2. The corrosion velocities of such samples in the 3.5 vol.% HCl, 15 wt% NaOH and 5 wt% NaCl solutions were 3.74, 2.98 and 0.50 g h-1 m-2 for 168, 336 and 336 h, respectively.
文摘The electrochemical performance of the anodes was measured in the reinforced concrete test block in artificial sea water. Their chemical composition,metallographic structure and surface morphology were analyzed. It was found that concrete mix proportion and the covering layer thickness had an impact on the performance of sacrificial anodes. The thermal-sprayed zinc alloy anodes had a more negative corrosion potential and larger galvanic current than metallurgy ones in the same conditions. They had similar chemical composition. But metallographic structure showed that the structure of thermal-sprayed zinc alloy anodes was a loose porous. This structure had the catalytic effect on the andes electrochemical reactions and made the anodes the electrochemical exchange current density increase and the corrosion potential move to negative direction.
