Hot Corrosion Behavior of Inconel 718 Without and With Aluminide Coating in Air Beneath a Thin Film of Salt Mixture of Na2SO4+5％NaCl
Aluminide coating was prepared on Inconel 718 superalloy by chemical vapor deposition(CVD).The hot corrosion behavior of Inconel 718 without and with aluminide coating beneath a thin film of salt mixture of Na2SO4(95％)+NaCl(5％)in air at 750,850 and 950℃ was studied respectively.The results indicate that Inconel 718 alloy shows poor corrosion resistance,and the higher the temperature,the more serious the corrosion.In the early stage of hot corrosion,the surface corrosion products are mainly composed of Cr2O3 and Fe2O3.As the corrosion time increases,spinel oxide becomes the main corrosion products.In addition,the scale on Inconel 718 alloy formed at 850 and 950℃ is loose and po-rous,while cracking and peeling were observed.For the aluminide coated alloy,it performs well with en-hanced corrosion resistance,while an Al2O3 scale is formed on the coating surface during corrosion.Al-though the coating underwent significant degradation with the increasing corrosion temperature and/or corrosion time.Besides,the formed corrosion scale is not tightly boned to the coating,while the defects such as cracks or voids are observed.Even so,the coating can still protect the substrate effectively to a great extent.
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