Salt-deposit hot corrosion behaviors of directionally solidified DZ466 superalloy
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摘要:
采用涂Na Cl/Na2SO4鹽方法研究了DZ466合金在850℃和950℃條件下熱腐蝕行為.結果表明:合金的腐蝕層包括三個區域,最外層為(Ni,Co)O氧化物層,次外層為尖晶石結構氧化層(Ni,Co)Cr2O4,內層為內腐蝕層,850℃時該層為Ni3S2,而950℃時除Ni3S2外,在靠近次外層還形成內氧化Al2O3;在850℃和950℃時合金的熱腐蝕機制相同,氧化膜連續性的破壞,是合金遭受熱腐蝕的主要原因;熱腐蝕增重曲線均符合拋物線規律,其速率常數分別為3.1×10-11g2·cm-4·s-1和1.5×10-9g2·cm-4·s-1,熱腐蝕激活能分別為179.2 k J·mol-1和138.3 k J·mol-1.
Abstract:Hot corrosion behaviors of DZ466 alloy at 850℃ and 950℃ were investigated by using a NaCl/Na2SO4salt-deposit method. It is found that there are three corrosion layers on the alloy. The outer and the middle layers consist of(Ni,Co) O oxide and(Ni,Co) Cr2O4 with a spinel structure,respectively. The innermost layer is an inner corrosion layer,which consists of Ni3S2 at 850℃,and the internal oxidation Al2O3 can be produced close to the middle layer at 950℃. The same hot corrosion mechanism is shown at 850℃ and 950℃. The destruction of the oxidation film continuity is a key reason for hot corrosion of the alloy. The hot corrosion weight gain curves obey a parabolic law at the two temperatures,the rate constants are 3.1×10-11g2·cm-4·s-1 and 1.5 × 10-9g2·cm-4·s-1,and the hot corrosion activation energies are 179.2 and 138.3 kJ ·mol-1at 850℃ and 950℃,respectively.
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Key words:
- superalloys /
- directional solidification /
- salt deposits /
- hot corrosion /
- corrosion films
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