By using newly developed CuNi5~25Ti16~28 B rapldly solidifled brazing filler the joining of Si3 N4/1.25Cr-0.5Mo steel has been carried out with interlayer method. If employing the interlayer structure of steel (0.2 mm...By using newly developed CuNi5~25Ti16~28 B rapldly solidifled brazing filler the joining of Si3 N4/1.25Cr-0.5Mo steel has been carried out with interlayer method. If employing the interlayer structure of steel (0.2 mm)/W (2.0 mm)/Ni(0.2 mm), the joint strength can be increased greatly compared with employing that of Ni/W/Ni, and the three point bend strength of the Joint shows the value of 261 MPa. The metallurgical behaviour at the interface between Si3N4 and the interlayer has been studied. It is found that Fe participated in the interfacial reactions between Si3N4 and the brazing filler at the Si3N4/steel (0.2 mm) interface and the compound Fe5Si3 was produced. However, since the reactions of Fe with the active Ti are weaker than those of Ni with Ti, the normal inter facial reactions were still assured at the interface of Si3N4/steel (0.2 mm) instead of Si3N4/Ni (0.2 mm), resulting in the improvement of the joint strength. The mechanism of the formation of Fe5Si3 is also discussed. Finally, some ideas to further ameliorate and simplify the interlayer structure are put forward.展开更多
The objective of this work was to study the effect of the heat treatment and further operation aging on the stereological parameters(size,quantity and volume fraction)of precipitates within ferrite grains of a creep-r...The objective of this work was to study the effect of the heat treatment and further operation aging on the stereological parameters(size,quantity and volume fraction)of precipitates within ferrite grains of a creep-resistant 1.25Cr0.5Mo steel after long-term operation.The heat treatment was similar to the treatment that is carried out in industrial steam pipelines after welding(post weld heat treatment-PWHT)during installation and/or repairing.The operation aging corresponds to a subsequent long in-service operation after repairing.To determine the stereological parameters,SEM digital images were taken from samples of this material after conditions of in-service-aged(after long-term operation),in-service-aged and heat-treated(simulating repairing)and in-service-aged,heat-treated and in-laboratory aged(simulating subsequent long-term operation after repairing).The results indicate that the changes in the stereological parameters of the precipitates within ferrite grains after PWHT is associated with the coarsening process of the within-ferrite-grain precipitates as well as stabilizing the microstructure,since the material aging after PWHT of an in-serviced aged material would not change the stereological parameters.展开更多
文摘By using newly developed CuNi5~25Ti16~28 B rapldly solidifled brazing filler the joining of Si3 N4/1.25Cr-0.5Mo steel has been carried out with interlayer method. If employing the interlayer structure of steel (0.2 mm)/W (2.0 mm)/Ni(0.2 mm), the joint strength can be increased greatly compared with employing that of Ni/W/Ni, and the three point bend strength of the Joint shows the value of 261 MPa. The metallurgical behaviour at the interface between Si3N4 and the interlayer has been studied. It is found that Fe participated in the interfacial reactions between Si3N4 and the brazing filler at the Si3N4/steel (0.2 mm) interface and the compound Fe5Si3 was produced. However, since the reactions of Fe with the active Ti are weaker than those of Ni with Ti, the normal inter facial reactions were still assured at the interface of Si3N4/steel (0.2 mm) instead of Si3N4/Ni (0.2 mm), resulting in the improvement of the joint strength. The mechanism of the formation of Fe5Si3 is also discussed. Finally, some ideas to further ameliorate and simplify the interlayer structure are put forward.
基金supported by the bilateral agreement CAPES-Brazil/MES–Cuba(project number 146/12)carried out at the Brazilian research laboratories LAPROSOLDA-LDTAD from Federal University of Uberlandia(UFU)DEMa-CCDM from Federal University of Sao Carlos(UFSCar)。
文摘The objective of this work was to study the effect of the heat treatment and further operation aging on the stereological parameters(size,quantity and volume fraction)of precipitates within ferrite grains of a creep-resistant 1.25Cr0.5Mo steel after long-term operation.The heat treatment was similar to the treatment that is carried out in industrial steam pipelines after welding(post weld heat treatment-PWHT)during installation and/or repairing.The operation aging corresponds to a subsequent long in-service operation after repairing.To determine the stereological parameters,SEM digital images were taken from samples of this material after conditions of in-service-aged(after long-term operation),in-service-aged and heat-treated(simulating repairing)and in-service-aged,heat-treated and in-laboratory aged(simulating subsequent long-term operation after repairing).The results indicate that the changes in the stereological parameters of the precipitates within ferrite grains after PWHT is associated with the coarsening process of the within-ferrite-grain precipitates as well as stabilizing the microstructure,since the material aging after PWHT of an in-serviced aged material would not change the stereological parameters.
