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RISS 인기검색어
- 검색키워드
- 저자 : Lu Xinhong (검색결과 2 건)
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Xilong Zhao,Kangming Ren,Xinhong Lu,Feng He,Yuekai Jiang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8
Ultrasonic impact treatment (UIT) was performed on the Ni-based alloy overlayer of austenitic stainless steel pipe girth weld. The difference of microstructure, microhardness and maximum shear strength distribution of the joint before and after UIT was studied by autobiographic test and shear punch test. The electrode potential data were tested by a threeelectrode electrochemical workstation and tafel curve was drawn. The results show that a grain refinement layer of about 30 um and a transition layer of about 60 um are formed in the overlayer of nickel-based alloy after UIT. Meanwhile, the transition layer has high corrosion sensitivity to oxalic acid solution, and the main precipitates in the overlayer are austenite and M23C6. In 3.5 % NaCl solution, the self-corrosion potential is -432 mV. The average microhardness of the overlayer of nickel-based alloy is 270 HV, which is 18.9 % higher than that of the sample without UIT. In the meantime, the maximum shear strength of nickel-based alloy is 955 MPa, which is 9.6 % higher than the sample without UIT. It is found that the ferrite is mainly lath and skeleton with no obvious change under UIT or not. Meanwhile, an average microhardness is 191 HV, and shear strength is 678 MPa. The microstructure of the welded joint is mainly consisted of austenite phase and ferrite phase, and FA solidification mode has been a major influence in the welding process. At the boundary between overlayer and circumferential welded joint of 304 austenitic stainless steel, reheat cracks in this area are occurred easily. Due to the migration of carbon, local martensite bands will be formed which will lead to large heterogeneity of microhardness.
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Zhao Xilong,Ren Kangming,Lu Xinhong,He Feng,Jiang Yuekai 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.11
Ultrasonic impact treatment (UIT) is carried out on the Ni-based alloy stainless steel pipe gas tungsten arc welding (GTAW) girth weld, the differences of microstructure, microhardness and shear strength distribution of the joint before and after ultrasonic shock are studied by microhardness test and shear punch test. The results show that after UIT, the plastic deformation layer is formed on the outside surface of the Ni-based alloy overlayer, single-phase austenite and g type precipitates are formed in the overlayer, and a large number of columnar crystals are formed on the bottom side of the overlayer. The average microhardness of the overlayer increased from 221 H V to 254 H V by 14.9%, the shear strength increased from 696 MPa to 882 MPa with an increase of 26.7% and the transverse average residual stress decreased from 102.71 MPa (tensile stress) to 18.33 MPa (compressive stress), the longitudinal average residual stress decreased from 114.87 MPa (tensile stress) to 84.64 MPa (compressive stress). The fracture surface has been appeared obvious shear lip marks and a few dimples. The element migrates at the fusion boundary between the Ni-based alloy overlayer and the austenitic stainless steel joint, which is leaded to form a local martensite zone and appear hot cracks. The welded joint is cooled by FA solidification mode, which is forming a large number of late and skeleton ferrite phase with an average microhardness of 190 H V and no obvious change in shear strength. The base metal is all austenitic phase with an average microhardness of 206 H V and shear strength of 696 MPa
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