GH3230合金超温循环氧化行为研究

Oxidative Behaviors of GH3230 Alloy Multi-Exposed to Ultra-high Temperatures

摘要:

试验测定了GH3230合金超温至1200 ℃循环氧化动力学，采用SEM、XRD和EPMA观察分析氧化行为及其对近表面层成分、组织的影响。结果表明，1200 ℃循环热暴露使合金持续产生氧化失重，失重速率由高变低再逐渐增加，但100次超温产生的减薄量小于板材厚度波动的控制限度；热暴露后表面残留氧化物主要是Cr2O3和MnCr2O4；碳氧化产生的气体形成的法向压力、氧化物生长应力的增大以及大温差冷却产生的热应力的叠加作用导致外层氧化膜的不断开裂、剥离。同时，沿晶界发生明显内氧化，但氧化脱碳形成的Ni基固溶体层远大于内氧化的深度，可抑制内氧化物的致脆效应。

Abstract:

The oxidation kinetics of GH3230 alloy was measured as a function of the cumulative time cyclically exposed upto 1200℃. The oxidation behaviors and the resulting composition and microstructure of the near surface layer were observed and analyzed by SEM, XRD and EPMA. It has been found that GH3230 alloy exhibits continuous oxidation weight loss during cyclic thermal exposures, and the weight loss rate decreases from the highest value to lowest level and then gradually increases with the thermal exposure time. Nevertheless, the alloy-thickness loss after 100 exposure cycles can be obviously less than the thickness-fluctuation limit of standardized plate products. The remaining oxides on the surface after heat exposure are mainly composed of Cr2O3 and MnCr2O4. The normal gas pressure produced by carbon oxidation, the increments of oxide growth stress and the thermal stress caused by over-temperature exposure lead to the cracking and spallation of the outer oxides. At mean time, internal oxidation occurs along grain boundaries significantly. While, it is worthy to note that the depth of the Ni-based solid solution layer tranformed through selective oxidation and oxidative decarbonization is always much larger than that of the internal oxidation. It indicates that the cracks initiated from the intergrannual oxides as the materials bearing tensile load will soon be blunted by in-front ductile FCC-stucture solid solution and therefore present negligible impact on the mechanical performance of GH3230 alloy.