Ni-based superalloys added with comparably higher concentrations of single-doped Hf and co-doped Hf/Y are prepared by vacuum induction melting(VIM).The oxidation properties up to 300 h at 900℃,1000℃,and 1100℃ are i...Ni-based superalloys added with comparably higher concentrations of single-doped Hf and co-doped Hf/Y are prepared by vacuum induction melting(VIM).The oxidation properties up to 300 h at 900℃,1000℃,and 1100℃ are investigated.The undoped alloy exhibited a minimum oxidation rate at 900℃ and 1000℃.The co-doped alloy showed a higher oxidation rate;however,it possesses better scale adhesion,and no spallation occurs.Hf-doped alloy showed a lower oxidation rate and better scale adhesion at 900℃ and 1000℃,but exhibited a shorter lifetime at 1100℃.The spallation of the Hf-doped alloy is attributed to the precipitation of the HfO2 in and beneath the oxide scale.The spallation in the undoped alloy is accredited to the thermal expansion mismatch between the growing oxide scale and superalloy substrate.Incorporating two reactive elements(REs)in alloy minimized the precipitation of RE oxide in the oxide scale,diminished internal oxidation in the alloy,and decreased oxide scale spallation.展开更多
Al2O3/Au nano-laminated composite coatings were prepared by means of magnetron sputtering. The coating was compact and comprised of nano-laminated Al2O3 and Au layers. High temperature cyclic oxidation test was employ...Al2O3/Au nano-laminated composite coatings were prepared by means of magnetron sputtering. The coating was compact and comprised of nano-laminated Al2O3 and Au layers. High temperature cyclic oxidation test was employed to investigate the oxidation resistance of the composite coatings. The results revealed that the applied Al2O3/Au nano-laminated composite coatings improved the oxidation and spallation resistance of the stainless steel substrate significantly. The mechanism accounting for oxidation resistance was related with the suppression of inward oxygen diffusion and selective oxidation of Cr in the substrate. The mechanism accounting for spallation resistance was attributed to the relaxation of thermal stress by the nano-laminated structure.展开更多
Nickel-based superalloys with and without Co by partial replacement of W were prepared using double vacuum melting.A comparison of the oxidation in air and hot corrosion behaviors under molten 75 wt.%Na2 SO4+25 wt.%Na...Nickel-based superalloys with and without Co by partial replacement of W were prepared using double vacuum melting.A comparison of the oxidation in air and hot corrosion behaviors under molten 75 wt.%Na2 SO4+25 wt.%NaCl at 900℃were systematically investigated.The results showed that partial replacement of W with Co promoted the formation of chromia scale and consequently decreased the oxidation rate.Besides,the addition of Co also retarded the internal oxidation/nitridation of Al and consequently promoted the growth of Al_(2) O3 scale,which further decreased the scaling rate and improved the adhesion of scale.Moreover,the addition of Co also further improved the hot corrosion resistance under molten Na2 SO4-NaCl salts.展开更多
基金funded by the National Natural Science Foundation of China under Grant No 51971214.
文摘Ni-based superalloys added with comparably higher concentrations of single-doped Hf and co-doped Hf/Y are prepared by vacuum induction melting(VIM).The oxidation properties up to 300 h at 900℃,1000℃,and 1100℃ are investigated.The undoped alloy exhibited a minimum oxidation rate at 900℃ and 1000℃.The co-doped alloy showed a higher oxidation rate;however,it possesses better scale adhesion,and no spallation occurs.Hf-doped alloy showed a lower oxidation rate and better scale adhesion at 900℃ and 1000℃,but exhibited a shorter lifetime at 1100℃.The spallation of the Hf-doped alloy is attributed to the precipitation of the HfO2 in and beneath the oxide scale.The spallation in the undoped alloy is accredited to the thermal expansion mismatch between the growing oxide scale and superalloy substrate.Incorporating two reactive elements(REs)in alloy minimized the precipitation of RE oxide in the oxide scale,diminished internal oxidation in the alloy,and decreased oxide scale spallation.
基金Project (50771021) supported by the National Natural Science Foundation of China
文摘Al2O3/Au nano-laminated composite coatings were prepared by means of magnetron sputtering. The coating was compact and comprised of nano-laminated Al2O3 and Au layers. High temperature cyclic oxidation test was employed to investigate the oxidation resistance of the composite coatings. The results revealed that the applied Al2O3/Au nano-laminated composite coatings improved the oxidation and spallation resistance of the stainless steel substrate significantly. The mechanism accounting for oxidation resistance was related with the suppression of inward oxygen diffusion and selective oxidation of Cr in the substrate. The mechanism accounting for spallation resistance was attributed to the relaxation of thermal stress by the nano-laminated structure.
基金financial supports from the Natural Science Foundation of Shandong Province,China(No.ZR2019MEE107)Shandong Jiaotong University“Climbing”Research Innovation Team Program,China(No.SDJTC1802)PhD Scientific Research Foundation of Shandong Jiaotong University,China(No.BS2018005)。
文摘Nickel-based superalloys with and without Co by partial replacement of W were prepared using double vacuum melting.A comparison of the oxidation in air and hot corrosion behaviors under molten 75 wt.%Na2 SO4+25 wt.%NaCl at 900℃were systematically investigated.The results showed that partial replacement of W with Co promoted the formation of chromia scale and consequently decreased the oxidation rate.Besides,the addition of Co also retarded the internal oxidation/nitridation of Al and consequently promoted the growth of Al_(2) O3 scale,which further decreased the scaling rate and improved the adhesion of scale.Moreover,the addition of Co also further improved the hot corrosion resistance under molten Na2 SO4-NaCl salts.
