Low and medium carbon steels were aluminized by the pack aluminizing technique using halideactivated pure-Al and Fe-Al packs. The effect of mixture composition, aluminizing temperatureand time and C content of the ste...Low and medium carbon steels were aluminized by the pack aluminizing technique using halideactivated pure-Al and Fe-Al packs. The effect of mixture composition, aluminizing temperatureand time and C content of the steel substrate on the structure and thickness of the aluminidelayer, and on the oxidation resistance was investigated. The optimum oxidation resistance canbe achieved with a low carbon steel substrate when the intermetallic phases Fe3Al and FeAlform the surface of the aluminide layer. In this case, the Al concentration at the surface of thealuminide coating is at least ≥15 wt pct. Formation of high Al concentration phases (FeAl3 andFe2Al5) during aluminizing should be avoided as they tend to embrittle the aluminide layer andreduce its oxidation resistance.展开更多
Experiments were conducted to investigate bed forms and flow resistance of light-weight sediment in an open channel flow. Three different synthetic materials of specific gravity 1. 055, 1. 46, each with uniform sizes ...Experiments were conducted to investigate bed forms and flow resistance of light-weight sediment in an open channel flow. Three different synthetic materials of specific gravity 1. 055, 1. 46, each with uniform sizes D50 for 1. 25mm, 1. 05mm, 1. 40mm were used. Some conclusions were obtained from the resultS of these experiments and the data of other reliable sources[1, 2, 3, 4]. They indicate that the grain resistence is greatly affected by D50, and bed form resistances is the function of the downstream slope and the height of the dune. As well as natural sand, Y is not only the function of Y', but also affected by the relative roughness Rb/D50 and the size of the sediment.展开更多
文摘Low and medium carbon steels were aluminized by the pack aluminizing technique using halideactivated pure-Al and Fe-Al packs. The effect of mixture composition, aluminizing temperatureand time and C content of the steel substrate on the structure and thickness of the aluminidelayer, and on the oxidation resistance was investigated. The optimum oxidation resistance canbe achieved with a low carbon steel substrate when the intermetallic phases Fe3Al and FeAlform the surface of the aluminide layer. In this case, the Al concentration at the surface of thealuminide coating is at least ≥15 wt pct. Formation of high Al concentration phases (FeAl3 andFe2Al5) during aluminizing should be avoided as they tend to embrittle the aluminide layer andreduce its oxidation resistance.
文摘Experiments were conducted to investigate bed forms and flow resistance of light-weight sediment in an open channel flow. Three different synthetic materials of specific gravity 1. 055, 1. 46, each with uniform sizes D50 for 1. 25mm, 1. 05mm, 1. 40mm were used. Some conclusions were obtained from the resultS of these experiments and the data of other reliable sources[1, 2, 3, 4]. They indicate that the grain resistence is greatly affected by D50, and bed form resistances is the function of the downstream slope and the height of the dune. As well as natural sand, Y is not only the function of Y', but also affected by the relative roughness Rb/D50 and the size of the sediment.
