To clarify the transformation mechanism of secondary phase and the mechanism of intergranular corrosion in laser welding Ni-based alloy (Hastelloy C-276)/304 stainless steel with filler wire,the secondary phase was an...To clarify the transformation mechanism of secondary phase and the mechanism of intergranular corrosion in laser welding Ni-based alloy (Hastelloy C-276)/304 stainless steel with filler wire,the secondary phase was analyzed by electron probe micro-analysis (EPMA) and transmission electron microscopy (TEM).The evaluation of intergranular corrosion resistance of the welded joints was conducted by double-loop electrochemical potentiokinetic reactivation(DL-EPR) method,and at the same time the chemical compositions of the corrosion surface were analyzed by energy-dispersive spectrometry (EDS).The results show that p phase has complete coherence relationship withμphase,and the coherent relationship is described as[001]p//■and[430]p//[0001]μ.Theμphase is rapidly transformed from p phase,which is the inhomogeneous phase transformation.The transformation of secondary phase will increase the susceptibility to intergranular corrosion.Therefore,the transformation of secondary phase should be avoided in the welding process.展开更多
By adopting the alloy wire of Ni 80 Cr 20 as the welding core and adding the alloy elements of B, Si, Mo and W into the outer plating covering, a new type of wear resistant overlay welding rod of Ni Cr B Si was develo...By adopting the alloy wire of Ni 80 Cr 20 as the welding core and adding the alloy elements of B, Si, Mo and W into the outer plating covering, a new type of wear resistant overlay welding rod of Ni Cr B Si was developed. This overlay welding rod has several properties such as low melting point and good fluidity. With low content of W and Mo, the wearability and crack resistance of the overlay welding rod can be increased, and the hardness can be increased to about HRC64. This kind of overlay rod has been applied to the overlay of wearable workpieces, such as the valves of high temperature, high pressure and the side plates of floor boarding brick die.展开更多
In the present work, the dissimilar joining of a Ti3Al-based alloy to a Ni-based superalloy was attempted by gas tungsten arc （GTA） welding technology. Sound joints were successfully achieved by using a Cu-Ni alloy ...In the present work, the dissimilar joining of a Ti3Al-based alloy to a Ni-based superalloy was attempted by gas tungsten arc （GTA） welding technology. Sound joints were successfully achieved by using a Cu-Ni alloy as filler material. According to X-ray energy dispersive spectroscopy and X-ray diffraction analysis results three transitional layers at the weld/Ti3Al interface were verified as follows： Ti2AlNb phase dissolved with Cu and Ni; Al（Cu,Ni）2Ti, （Cu,Ni）2Ti and （Nb, Ti） solid solution; Cu-rich phase and a complex multi-element phase. The In718/weld interface is characterized by solid solutions of Ni, Cu, Cr, Fe and Nb. The average tensile strength of the as-welded joints at room temperature is 163 MPa, and after a post-weld heat treatment it is increased slightly to 177 MPa. The fracture occurred at the surfacial layer of the joined Ti3Al base alloy, indicating that the Ti2AINb layer dissolved with Cu and Ni is the weak link of the Ti3Al/In718 joint.展开更多
Materials-development projects for advanced ultra-supercritical(A-USC) power plants with steam temperatures of 700℃ and above have been performed in order to achieve high efficiency and low CO_2 emissions in Europe, ...Materials-development projects for advanced ultra-supercritical(A-USC) power plants with steam temperatures of 700℃ and above have been performed in order to achieve high efficiency and low CO_2 emissions in Europe, the US, Japan, and recently in China and India as well. These projects involve the replacement of martensitic 9%–12% Cr steels with nickel(Ni)-base alloys for the highest temperature boiler and turbine components in order to provide sufficient creep strength at 700℃ and above. To minimize the requirement for expensive Ni-base alloys, martensitic 9%–12% Cr steels can be applied to the next highest temperature components of an A-USC power plant, up to a maximum of 650℃. This paper comprehensively describes the research and development of Ni-base alloys and martensitic 9%–12% Cr steels for thick section boiler and turbine components of A-USC power plants, mainly focusing on the long-term creep-rupture strength of base metal and welded joints, strength loss in welded joints, creep-fatigue properties, and microstructure evolution during exposure at elevated temperatures.展开更多
基金The authors would like to acknowledge the financial support from National Key Research and Development Program of China(2018YFB1107801 and 2018YFB1107802)Science Fund for Creative Research Groups of NSFC(51621064)+1 种基金National Natural Science Foundation of China(51790172)Fundamental Research Funds for the Central University(DUT19LAB06).
文摘To clarify the transformation mechanism of secondary phase and the mechanism of intergranular corrosion in laser welding Ni-based alloy (Hastelloy C-276)/304 stainless steel with filler wire,the secondary phase was analyzed by electron probe micro-analysis (EPMA) and transmission electron microscopy (TEM).The evaluation of intergranular corrosion resistance of the welded joints was conducted by double-loop electrochemical potentiokinetic reactivation(DL-EPR) method,and at the same time the chemical compositions of the corrosion surface were analyzed by energy-dispersive spectrometry (EDS).The results show that p phase has complete coherence relationship withμphase,and the coherent relationship is described as[001]p//■and[430]p//[0001]μ.Theμphase is rapidly transformed from p phase,which is the inhomogeneous phase transformation.The transformation of secondary phase will increase the susceptibility to intergranular corrosion.Therefore,the transformation of secondary phase should be avoided in the welding process.
文摘By adopting the alloy wire of Ni 80 Cr 20 as the welding core and adding the alloy elements of B, Si, Mo and W into the outer plating covering, a new type of wear resistant overlay welding rod of Ni Cr B Si was developed. This overlay welding rod has several properties such as low melting point and good fluidity. With low content of W and Mo, the wearability and crack resistance of the overlay welding rod can be increased, and the hardness can be increased to about HRC64. This kind of overlay rod has been applied to the overlay of wearable workpieces, such as the valves of high temperature, high pressure and the side plates of floor boarding brick die.
文摘In the present work, the dissimilar joining of a Ti3Al-based alloy to a Ni-based superalloy was attempted by gas tungsten arc （GTA） welding technology. Sound joints were successfully achieved by using a Cu-Ni alloy as filler material. According to X-ray energy dispersive spectroscopy and X-ray diffraction analysis results three transitional layers at the weld/Ti3Al interface were verified as follows： Ti2AlNb phase dissolved with Cu and Ni; Al（Cu,Ni）2Ti, （Cu,Ni）2Ti and （Nb, Ti） solid solution; Cu-rich phase and a complex multi-element phase. The In718/weld interface is characterized by solid solutions of Ni, Cu, Cr, Fe and Nb. The average tensile strength of the as-welded joints at room temperature is 163 MPa, and after a post-weld heat treatment it is increased slightly to 177 MPa. The fracture occurred at the surfacial layer of the joined Ti3Al base alloy, indicating that the Ti2AINb layer dissolved with Cu and Ni is the weak link of the Ti3Al/In718 joint.
文摘Materials-development projects for advanced ultra-supercritical(A-USC) power plants with steam temperatures of 700℃ and above have been performed in order to achieve high efficiency and low CO_2 emissions in Europe, the US, Japan, and recently in China and India as well. These projects involve the replacement of martensitic 9%–12% Cr steels with nickel(Ni)-base alloys for the highest temperature boiler and turbine components in order to provide sufficient creep strength at 700℃ and above. To minimize the requirement for expensive Ni-base alloys, martensitic 9%–12% Cr steels can be applied to the next highest temperature components of an A-USC power plant, up to a maximum of 650℃. This paper comprehensively describes the research and development of Ni-base alloys and martensitic 9%–12% Cr steels for thick section boiler and turbine components of A-USC power plants, mainly focusing on the long-term creep-rupture strength of base metal and welded joints, strength loss in welded joints, creep-fatigue properties, and microstructure evolution during exposure at elevated temperatures.
