具保護塗層之Hastelloy X超合金鋁化處理之熱腐蝕性能評估

Hot Corrosion Properties Evaluation of Aluminized Hastelloy X with Different Bond Coatings

本研究以高速火燄噴銲法與電漿噴焊法於Hastelloy X超合金上分別披覆CoNiCrAlY塗層與NiCrAlY塗層，後者並以電子束披覆7.5 µm厚的白金層。兩試樣再利用850℃，4小時之固體滲鋁，在表面分別生成CoAl與PtAl2相。由900℃之90 wt%Na2SO4與10 wt%NaCl混合熔融鹽浸泡10小時與48小時的熱腐蝕試驗結果得知，未鋁化處理之兩種試樣均無法抵抗熱腐蝕介質之侵蝕而被完全貫穿。以電漿噴焊法與電子束披覆之NiCrAlY-Pt塗層經過鋁化處理後表面雖然生成保護性之氧化鋁層，但是由於表面之縫隙與孔洞缺陷太多，使得該試樣仍然無法長時間抵抗熱腐蝕而被完全貫穿。以高速火燄噴銲法披覆生成的CoNiCrAlY塗層經過滲鋁處理之後在表面生成緻密保護之氧化鋁層，能長時間有效隔絕腐蝕介質入侵，具有絕佳之抗熱腐蝕特性。

The CoNiCrAlY and NiCrAlY surface layers were deposited on Hastelloy X superalloys by high velocity oxygen fuel spraying and plasma spraying processes, respectively. Platinum thin film around 7.5 m thick was further coated on the surface of NiCrAlY layer by electron beam deposition process. Two kinds of specimens were pack aluminized at 850℃ for 4 hours to produce CoAl and PtAl2 phases on the surface, individually. It's observed that the Hastelloy X with sole CoNiCrAlY or NiCrAlY-Pt coating was totally penetrated by the 90 wt%Na2SO4 and 10 wt%NaCl mixed molten salt at 900℃ for 10 and 48 hours. Even though the alumina layer was produced on the surface of NiCrAlY-Pt coated and aluminized specimen immersed in the mixed molten salt at 900℃for 10 hours, it was still penetrated by the molten salt after 48 hours. The surface defects and voids are responsible for the corrosion resistance degradation of the aluminized NiCrAlY-Pt specimen. For the specimen with CoNiCrAlY coating and aluminizing treatments, sufficient hot corrosion resistance was achieved due to the dense and protective alumina layer formed on the surface to retard the attack of mixed molten salt at 900℃ for 10 and 48 hours.