不同表面处理的H13钢耐铝液腐蚀的对比分析

H13钢试样经真空热处理后,分别对其进行渗氮和碳氮硫共渗处理,然后浸入700 ℃高温熔融铝液中进行腐蚀试验,并对腐蚀前后试样的截面组织形貌、质量损失及相成分进行了详细分析。结果表明:渗氮试样与碳氮硫共渗试样的渗层界面结合方式相似,渗层光滑致密,与基体分界较为平整。碳氮硫共渗试样的表面化合物区存在Fe₃N、Fe₂N、FeS、Fe₃C相,其中FeS相是典型的密排六方晶体结构,且硬度较高;渗氮试样表面化合物区存在Fe₃N、Fe₂N相,渗层的表面硬度高于碳氮硫共渗试样。在相同的腐蚀条件下,真空热处理试样的质量损失为7.5 g,质量损失率为21.1%,渗氮试样的质量损失为4.1 g,质量损失率为11.2%,碳氮硫共渗试样的质量损失为0.8 g,质量损失率为2.2%。试样中的铁铝化合物呈锯齿状嵌入基体,厚度分别为184.75、88.56和35.88 μm;经铝液腐蚀后的主要化合物均为Fe₂Al₅,其中碳氮硫共渗试样由于S、C的加入,可与H13钢基体形成FeS和Fe₃C,表现出最佳的耐高温铝液腐蚀性能。

Comparative analysis of corrosion resistance in molten aluminum of H13 steel with different surface treatments

H13 steel specimens were subjected to nitriding and sulphonitrocarburizing treatments after vacuum heat treatment,and then immersed in 700℃high temperature molten aluminum for corrosion test.And the cross-section microstructure,mass loss and phase composition of the specimens before and after corrosion were analyzed in detail.The results show that the interface bonding mode of infiltration layer is similar for the nitrided specimen and the sulphonitrocarburizing specimen,which is smooth and dense,the boundary between layer and matrix is relatively flat.There are Fe₃N,Fe₂N,FeS,Fe₃C phases in the surface compound area of the sulphonitrocarburized specimen,with the FeS phase being a typical close-packed hexagonal crystal structure with higher hardness.There are Fe₃N and Fe₂N phases in the surface compound area of the nitrided specimen,and the surface hardness of which is higher than that of the sulphonitrocarburized specimen.Under the same corrosion conditions,the mass loss and mass loss rate of the vacuum heat treated specimen are 7.5 g and 21.1%,respectively,those of the nitrided specimen are 4.1 g and 11.2%,respectively,those of the sulphonitrocarburized specimen are 0.8 g and 2.2%,respectively.The iron-aluminum compound of the specimens is embedded in the steel matrix in a zigzag shape,and the thickness is 184.75,88.56 and 35.88μm,respectively.The main compound after corrosion by molten aluminum is Fe₂Al₅,and the sulphonitrocarburized specimen can form FeS and Fe₃C with the H13 steel matrix due to the addition of S and C,showing the best high temperature corrosion resistance in molten aluminum.