825合金热挤压管中碳化物的析出及回溶行为

Precipitation and Dissolution of Carbide in Hot Extruded Pipe of 825 Alloy

研究了825合金热挤压管中碳化物的时效析出及回溶行为。结果表明,在750～800℃时效时,沿晶界会大量析出M23C6型碳化物,造成晶界附近Cr元素贫化,从而显著降低该合金的抗晶间腐蚀能力;晶内则几乎不出现M23C6型碳化物。固溶热处理试验结果表明,M23C6碳化物的溶解温度为950～980℃。在该温度下固溶20 min以上,可将M23C6型碳化物充分溶解,赋予合金良好的抗晶间腐蚀能力。

The behavior of carbide precipitation and dissolution in hot extruded pipe of 825 alloy was investigated by aging and solution treatment. The results show that M23C6 type carbides appear after aging at 750-800 ℃, and a narrow chromium-depleted zone adjacent to the grain boundary appears. Thus, the inter-granular corrosion resistant of 825 alloy deteriorates obviously and the corrosion rate is higher than the technical requirement. But, in the alloy matrix, M23C6 type carbide can not be found. The solution annealing microstructures show that the dissolution temperature of M23C6 type carbide is 950-980 ℃. The 825 alloy has a good resistance of inter-granular corrosion when solution at 950-980℃ for more than 20 min.