A practical process method for precise integration of SiC_(f)/SiC composite(CMC)and a Ni-based superalloy(K403)was proposed in this study.It involves Nb coating pretreatment of the CMC via the chemical vapor depositio...A practical process method for precise integration of SiC_(f)/SiC composite(CMC)and a Ni-based superalloy(K403)was proposed in this study.It involves Nb coating pretreatment of the CMC via the chemical vapor deposition(CVD)at 1000℃and subsequent integral precision casting between the pretreated CMC and the K403 superalloy melt.The method solves the difficulty for the dissimilar material to be cast together,forming a robust bonding interface with an average shear strength of 94.8 MPa at room temperature.During the pretreatment process,the Nb reacted with the CMC,forming a reactive coating with the microstructure composed of NbC,Nb2C and Nb5Si3 phases.In the following integral casting,the Nb reactive coating effectively blocked detrimental graphitization reaction between the Ni element in the superalloy melt and the CMC,and mitigated the interface thermal stress generated by both the mismatch of thermal expansion coefficients and temperature difference,resulting in the increase of interfacial strength.The typical interfacial microstructure consists of the CMC,NbC,NbSi_(2)/NbC,SiC,NbSi_(2),Nb_(2)C,Nb_(5)Si_(3),Al_(4)C_(3),Nb_(2)Al/γ/γ'and MC(M=W,Mo,Ti).A formula for estimating the interfacial thermal stress of an integrated cast was derived.展开更多
Surface engineering technology is a suitable method for coatings on the metal surfaces or performing surface modification treatment, which can improve corrosion resistance and biocompatibility of metals. In this resea...Surface engineering technology is a suitable method for coatings on the metal surfaces or performing surface modification treatment, which can improve corrosion resistance and biocompatibility of metals. In this research, corrosion behavior of Nb coating on H2SO4 and HNO3 treated AISI stainless steel 316L （SS） was evaluated. Nb coating was carried out using physical vapor deposition process on the SS. Characterization techniques including scanning electron microscopy （SEM） and energy dispersive X-ray （EDX） technique were used to investigate the microstructure and morphology of the coated and treated SS. Electrochemical potentiodynamic tests were performed in two types of physiological solutions and compared with the pristine SS specimens. Cyclic polarization tests were performed to evaluate resistivity against pitting. Experimental results indicate that Nb coating and surface treatment of the SS had a positive effect on improvement of corrosion behavior. The decrease in corrosion current densities was significant for coated and treated specimens. The corrosion current density was much lower than the values obtained for pristine specimens.展开更多
Cr poison is the main cause of rapid performance degradation of solid oxide fuel cell(SOFC)stack from Cr-based ferritic stainless steel(FSS).Surface coating is an effective method to inhibit outward diffusion of Cr,co...Cr poison is the main cause of rapid performance degradation of solid oxide fuel cell(SOFC)stack from Cr-based ferritic stainless steel(FSS).Surface coating is an effective method to inhibit outward diffusion of Cr,contributing to reducing volatilization of Cr-containing compounds.In this work,Ti(Nb)-Si-C protective coating is prepared on surface of SUS 430 by DC magnetron sputtering with a dense and uniform structure.The coated samples possess greatly enhanced oxidation resistance(k_(p)=1.1×10^(-14)g^(2)·cm^(-4)·s^(-1))compared to bare alloy.Moreover,Ti-and Si-rich and Cr depleted outer oxide layer formed on the top surface of the alloy,which contributes to reducing the outward diffusion and volatilization of Cr.In addition,the thin oxide layers on surface of the coated alloy exhibit excellent electrical properties with an ASR value of 12.8 mΩ·cm^(2)after oxidation at 800℃in air for 500 h.展开更多
基金the financial support from the Fundamental Research Funds for the Central Universities,China(No.FRF-GF-18-006A)。
文摘A practical process method for precise integration of SiC_(f)/SiC composite(CMC)and a Ni-based superalloy(K403)was proposed in this study.It involves Nb coating pretreatment of the CMC via the chemical vapor deposition(CVD)at 1000℃and subsequent integral precision casting between the pretreated CMC and the K403 superalloy melt.The method solves the difficulty for the dissimilar material to be cast together,forming a robust bonding interface with an average shear strength of 94.8 MPa at room temperature.During the pretreatment process,the Nb reacted with the CMC,forming a reactive coating with the microstructure composed of NbC,Nb2C and Nb5Si3 phases.In the following integral casting,the Nb reactive coating effectively blocked detrimental graphitization reaction between the Ni element in the superalloy melt and the CMC,and mitigated the interface thermal stress generated by both the mismatch of thermal expansion coefficients and temperature difference,resulting in the increase of interfacial strength.The typical interfacial microstructure consists of the CMC,NbC,NbSi_(2)/NbC,SiC,NbSi_(2),Nb_(2)C,Nb_(5)Si_(3),Al_(4)C_(3),Nb_(2)Al/γ/γ'and MC(M=W,Mo,Ti).A formula for estimating the interfacial thermal stress of an integrated cast was derived.
基金support of this research by Isfahan University of technology
文摘Surface engineering technology is a suitable method for coatings on the metal surfaces or performing surface modification treatment, which can improve corrosion resistance and biocompatibility of metals. In this research, corrosion behavior of Nb coating on H2SO4 and HNO3 treated AISI stainless steel 316L （SS） was evaluated. Nb coating was carried out using physical vapor deposition process on the SS. Characterization techniques including scanning electron microscopy （SEM） and energy dispersive X-ray （EDX） technique were used to investigate the microstructure and morphology of the coated and treated SS. Electrochemical potentiodynamic tests were performed in two types of physiological solutions and compared with the pristine SS specimens. Cyclic polarization tests were performed to evaluate resistivity against pitting. Experimental results indicate that Nb coating and surface treatment of the SS had a positive effect on improvement of corrosion behavior. The decrease in corrosion current densities was significant for coated and treated specimens. The corrosion current density was much lower than the values obtained for pristine specimens.
基金supported by the National Natural Science Foundation of China (52001179)the Natural Science Foundation of Shandong Province (ZR2020ME019)
文摘Cr poison is the main cause of rapid performance degradation of solid oxide fuel cell(SOFC)stack from Cr-based ferritic stainless steel(FSS).Surface coating is an effective method to inhibit outward diffusion of Cr,contributing to reducing volatilization of Cr-containing compounds.In this work,Ti(Nb)-Si-C protective coating is prepared on surface of SUS 430 by DC magnetron sputtering with a dense and uniform structure.The coated samples possess greatly enhanced oxidation resistance(k_(p)=1.1×10^(-14)g^(2)·cm^(-4)·s^(-1))compared to bare alloy.Moreover,Ti-and Si-rich and Cr depleted outer oxide layer formed on the top surface of the alloy,which contributes to reducing the outward diffusion and volatilization of Cr.In addition,the thin oxide layers on surface of the coated alloy exhibit excellent electrical properties with an ASR value of 12.8 mΩ·cm^(2)after oxidation at 800℃in air for 500 h.
