Alloys containing chromium （Cr） and molybdenum （Mo）, as the major alloying elements, are widely used in various industries where the material experiences corrosive environments. Chromium （Cr）, when added in an o...Alloys containing chromium （Cr） and molybdenum （Mo）, as the major alloying elements, are widely used in various industries where the material experiences corrosive environments. Chromium （Cr）, when added in an optimum amount, forms a Cr203 passive film which protects the underlying metal in aggressive solutions. Molybdenum （Mo） forms its oxides in the low pH solutions, thus, enhances the uniform corrosion resistance of an alloy in reducing acids and assists in inhibition to localized corrosion. Minor alloying elements, like tungsten （W） and copper （Cu）, also improve the overall corrosion resistance of an alloy in specific solutions. In the present study, corrosion resistance behavior of commercial iron- based alloys （316L SS, 254 SMO and 20Cb3） and nickel-based alloys （Mone1400, Alloy 625 and C-276） was studied in the acidic solutions. While the corrosion behavior of wrought alloys has been widely studied, there is little to no information on the corrosion performance of their welds, typically being the weak regions for corrosion initiation and propagation. Therefore, an attempt was undertaken to investigate the uniform and localized corrosion performance of base metal, simulated heat-affected zone and all-weld-metal samples of a Ni-Cr-Mo-W alloy, C-276. The study was conducted in aggressive acidic solutions. Various corrosion and surface analytical techniques were utilized to analyze the results.展开更多
The characteristics of inclusions in two types of low-carbon steels by different deoxidization methods have been investigated by using the welding thermal simulation, the optical microscopy and scanning electron micro...The characteristics of inclusions in two types of low-carbon steels by different deoxidization methods have been investigated by using the welding thermal simulation, the optical microscopy and scanning electron microscopy. In addition, the effects of inclusions on microstructure and properties of heat-affected-zone were studied. The nucleation and growth of intragranular acicular ferrite was observed in situ by the laser scanning confocal microscopy. The distribution of Mn element near the inclu- sion was also analyzed by the auger electron spectroscopy. The results showed that the inclusions in A1 killed steel are mainly aluminum oxides, manganese sulfide and titanium nitrides, and that the inclusions in Ti killed steel are mainly titanium oxide, manganese sulfide complex inclusion and single manganese sulfide. The auger electron spectroscopy showed that there is an Mn-depleted zone near the interface of TiOffMnS complex inclusion in the size of 1-3 gm. It could be the effective nucleus of intragranular acicular ferrite which could divide the prior austenite grains, inhibit the growth of low-temperature microstruc- ture, and refine the final microstructure, so as to improve the toughness of heat-affected-zone significantly.展开更多
对NiCrMoV转子钢焊接接头,将初始裂纹置于热影响区的完全淬火-回火区、不完全淬火-回火区和回火区,基于扫描电镜(Scanning electron microscopy,SEM)-微拉伸试验装置,开展真空条件下疲劳短裂纹扩展行为的原位试验,研究焊接接头热处理后...对NiCrMoV转子钢焊接接头,将初始裂纹置于热影响区的完全淬火-回火区、不完全淬火-回火区和回火区,基于扫描电镜(Scanning electron microscopy,SEM)-微拉伸试验装置,开展真空条件下疲劳短裂纹扩展行为的原位试验,研究焊接接头热处理后微区的疲劳破坏机理。结果表明,热影响区内疲劳物理短裂纹的扩展是不连续的,K仍可作为裂纹扩展的驱动参量,材料强度水平控制疲劳短裂纹扩展方向。在完全淬火-回火区,短裂纹扩展受到大尺寸晶粒和板条马氏体的影响,裂纹易偏折,疲劳抗力最好;而回火区的晶粒尺寸和强度较小,疲劳门槛值较低,裂纹抗力较弱。在不完全淬火-回火区,晶界析出碳化物较多,疲劳裂纹主要以沿晶方式扩展,裂纹扩展抗力最差。展开更多
文摘Alloys containing chromium （Cr） and molybdenum （Mo）, as the major alloying elements, are widely used in various industries where the material experiences corrosive environments. Chromium （Cr）, when added in an optimum amount, forms a Cr203 passive film which protects the underlying metal in aggressive solutions. Molybdenum （Mo） forms its oxides in the low pH solutions, thus, enhances the uniform corrosion resistance of an alloy in reducing acids and assists in inhibition to localized corrosion. Minor alloying elements, like tungsten （W） and copper （Cu）, also improve the overall corrosion resistance of an alloy in specific solutions. In the present study, corrosion resistance behavior of commercial iron- based alloys （316L SS, 254 SMO and 20Cb3） and nickel-based alloys （Mone1400, Alloy 625 and C-276） was studied in the acidic solutions. While the corrosion behavior of wrought alloys has been widely studied, there is little to no information on the corrosion performance of their welds, typically being the weak regions for corrosion initiation and propagation. Therefore, an attempt was undertaken to investigate the uniform and localized corrosion performance of base metal, simulated heat-affected zone and all-weld-metal samples of a Ni-Cr-Mo-W alloy, C-276. The study was conducted in aggressive acidic solutions. Various corrosion and surface analytical techniques were utilized to analyze the results.
基金supported by the National Basic Research Program of China ("973" Program) (Grant No. 2010CB630801)
文摘The characteristics of inclusions in two types of low-carbon steels by different deoxidization methods have been investigated by using the welding thermal simulation, the optical microscopy and scanning electron microscopy. In addition, the effects of inclusions on microstructure and properties of heat-affected-zone were studied. The nucleation and growth of intragranular acicular ferrite was observed in situ by the laser scanning confocal microscopy. The distribution of Mn element near the inclu- sion was also analyzed by the auger electron spectroscopy. The results showed that the inclusions in A1 killed steel are mainly aluminum oxides, manganese sulfide and titanium nitrides, and that the inclusions in Ti killed steel are mainly titanium oxide, manganese sulfide complex inclusion and single manganese sulfide. The auger electron spectroscopy showed that there is an Mn-depleted zone near the interface of TiOffMnS complex inclusion in the size of 1-3 gm. It could be the effective nucleus of intragranular acicular ferrite which could divide the prior austenite grains, inhibit the growth of low-temperature microstruc- ture, and refine the final microstructure, so as to improve the toughness of heat-affected-zone significantly.
文摘对NiCrMoV转子钢焊接接头,将初始裂纹置于热影响区的完全淬火-回火区、不完全淬火-回火区和回火区,基于扫描电镜(Scanning electron microscopy,SEM)-微拉伸试验装置,开展真空条件下疲劳短裂纹扩展行为的原位试验,研究焊接接头热处理后微区的疲劳破坏机理。结果表明,热影响区内疲劳物理短裂纹的扩展是不连续的,K仍可作为裂纹扩展的驱动参量,材料强度水平控制疲劳短裂纹扩展方向。在完全淬火-回火区,短裂纹扩展受到大尺寸晶粒和板条马氏体的影响,裂纹易偏折,疲劳抗力最好;而回火区的晶粒尺寸和强度较小,疲劳门槛值较低,裂纹抗力较弱。在不完全淬火-回火区,晶界析出碳化物较多,疲劳裂纹主要以沿晶方式扩展,裂纹扩展抗力最差。
