Abstract Micron-TiN particles and Ti powder were introduced into the AgCu powder filler to design a particle-reinforced composite filler. This TiN particle (TiNp) modified brazing material was adopted to reliably braze Si3N4 ceramics onto 42CrMo steel, and the ratio of active element Ti to TiNp reinforcement was optimized for joint strength improvement. The reaction layer’s thickness (TiN+Ti5Si3) adjacent to the ceramic decreased by introducing TiNp. Nevertheless, the reaction layer’s thickness (TiC) at the 42CrMo side did not vary too much. TiNp showed excellent wettability with Ag-Cu-Ti braze, and there was no obvious reaction at the interface. Cu-Ti intermetallic compounds were formed and randomly distributed in the brazing seam. When the TiNp content did not exceed 8 vol.%, the joints’ mechanical properties first sharply decreased and then remained basically unchanged when Ti increased. Raising the TiNp content to 10 vol.%, the joint strength showed the changing trends of first increasing and then dropping by increasing Ti content. The bending strength reached the maximum value of 396 MPa when 8 vol.% TiNp and 4 wt.% Ti were adopted.

In order to identify the main causes of cracking and leakage of 12Cr1MoV water wall tubes outside the furnace in thermal power plants, this paper uses macroscopic morphology observation, stereomicroscope observation, alloy composition analysis, Brinell hardness test, metallographic structure inspection, and other means to detect and analyze the failed water wall tube. The alloy composition content of the water wall tubes submitted for inspection is within the standard requirements, and the Brinell hardness value of the water wall tubes also meets the requirements of relevant standards, The matrix metallographic structure of the water wall tube is normal. The initial leakage point is the cracking of the fillet weld at the end of the water wall tube fin, while other leakage points are caused by the blowing of the medium leaked from the initial leakage point. The initial leakage point is formed by the fatigue crack initiated at the fillet weld of the fin end and the corrosion crack on the inner wall extending towards each other. It is recommended to further inspect whether there is still cracking at the end of adjacent water wall tube fins to prevent similar cracking from happening again. Due to the frequent changes in the “peak shaving” period and amplitude in recent years, it is necessary to design the peak shaving period or amplitude reasonably to ensure the safe operation of the boiler.

某沿海变电站66 kV复合式气体绝缘金属封闭开关(HGIS)套管接线端子一侧的镀银层出现大面积腐蚀剥落现象.采用宏观形貌观察、化学成分分析、金相检验和扫描电镜等试验方法,结合服役地区大气环境数据对镀银层失效原因进行了研究分析.结果表明:起泡及剥离的镀银层已发生氧化或者硫化,暴露出来的铝合金基材已被氧化;腐蚀介质通过镀银层表面凹坑、划痕或界面孔隙等通道进入镀层与基体界面是导致接线端子镀银层腐蚀脱落的主要原因.

Q235 steel /Al 2 O 3 ceramics were brazed with Ag-CuO filler metal at 1050°C and held for 15min in air. When brazing Q235 steel and Al 2 O 3 ceramics directly, it was found that serious oxidation occurred on the steel side during the brazing process. Although the joining was realized, a loose oxide film was formed on the surface of the base steel, which affected the mechanical properties of joints. When Q235 steel with aluminized surface was adopted to braze with Al 2 O 3 ceramics, a Al 2 O 3 layer formed on the surface of Q235 steel successfully avoided the oxidation of Q235 steel, and a compact and defection-free joint was obtained. The typical organization of joint was Al 2 O 3 / CuAl 2 O 4 / CuO/ Ag/ CuO/ CuAl 2 O 4 /Al 2 O 3 / FeAl/ FeAl 2 / Fe.

The methods of chemical composition analysis, macroscopic morphology inspection, metallographic inspection, scanning electron microscope and energy spectrum analysis are used to analyze the failed condenser brass tubes. The results show that the alloy composition of the condenser tube meets the requirements of the HSn70-1A brass standard. There are many traces of pitting corrosion on the inner surface. The metallographic observation shows that the pitting corrosion is cracking along thegrain boundary, only about 1-3 grains deep. Energy spectrum analysis shows that the content of O, Ca, and P, and a small amount of Cl and S in the corrosion pits are greatly increased, and the zinc content is significantly decreased. Condenser tube leakage is mainly caused by circulating water pollution, until the corrosion penetrates to form a leak. According to the corrosion characteristics, this article puts forward relevant suggestions for the protection of condenser tubes.

Abstract A turbine intermediate regulating valve fractured in a power plant, and the reasons for the fracture were analysed by using macro morphology observation, mechanical properties test, chemical composition analysis and microstructure observation, such as scanning electron microscopy (SEM) analysis or metallographic analysis. The results indicated that the chemical composition and strength properties were in accordance with the standard requirements, but the elongation after fracture and the impact toughness value were all lower than the required values. Precipitation of σ phase further weakened the matrix and reduced the strength of the structure. Fretting friction and collision appeared between the valve stem and the anti-rotating pin, and additional stress was generated by the reduction of radial clearance between the pin and valve. Then cracks and brittle expansion occurred in the stress concentration areas close to the anti-rotating pin holes and finally fractured.

采用宏观形貌观察、化学成分分析、金相组织观察等方法,结合实际服役地区大气环境分析,对某沿海变电站66 kV HGIS设备套管接线板镀银层大面积腐蚀剥落现象进行研究。结果表明:镀银层出现起泡、剥离的位置全部为基体与Cu过渡层之间,而银层与Cu过渡层之间结合良好;起泡及剥离的镀层已发生氧化或者硫化,暴露出来的铝合金基材被氧化。腐蚀介质通过镀层表面划痕或界面孔隙等通道进入镀层与基体界面形成腐蚀是导致接线板镀银层腐蚀脱落的主要原因。

The corrosion failure analysis of the brass tube in a power plant condenser was conducted by the methods of chemical composition analysis, macro morphology inspection of the leakage point, metallurgical examination, scanning electron microscope and energy spectrum analysis etc. The results indicated that the failure of the brass tube was due to the erosion of the internal surface. The zinc content in the etching pits decreased obviously and dezincification corrosion could be classified. Some suggestions for anti-corrosion measures of the brass tubes were put forward.