本研究使用鈷基超合金Haynes 188於750、800及850 ℃靜滯空氣中進行氯化鈉沉積鹽高溫腐蝕試驗，探討含氯化鈉環境下的高溫腐蝕機制。
實驗結果顯示， Haynes 188氯化鈉腐蝕後生成的氧化皮膜不具保護性。Haynes 188 在750~850 ℃溫度間會在晶界上析出Cr23C6， Cr23C6優先與氯反應分解產生嚴重之沿晶腐蝕，並在腐蝕路徑形成鉻耗乏區。隨時間的增加，氯化物的揮發造成皮膜與基材間氯分壓降低，進而使腐蝕反應速率減緩。溫度愈高氯化物揮發愈加明顯，因此850 ℃之動力學曲線較800 ℃早進入腐蝕反應較慢的第二階段中。Haynes 188含14%鎢，鎢經氯化鈉高溫腐蝕所形成的氧化物及氯化物當實驗溫度超過750 ℃後都具有相當高的揮發性，反映在動力學曲線上呈現了明顯的重量損失(weight loss)。
與先前鐵基合金之氯化鈉高溫腐蝕研究比較，對合金基材元素而言，鈷具有較鐵高的抗氯化鈉腐蝕性；對430、304、310、253MA、353MA、Haynes 188六種合金而言，添加鎳較添加鉻能提升合金對氯化鈉腐蝕的抗性。

The purpose of this work is to study the hot-corrosion behavior of a Co-based superalloy (Haynes 188; HA-188) over the temperature range of 750 – 850 ℃ in static air with a 2 mg/cm2 NaCl deposit, and in particular, to systematically understand the hot-corrosion mechanism of the alloy.
The results showed that the oxide-scales formed on the HA-188 alloy after hot corrosion were nonprotective. In addition, the precipictates of Cr23C6 along grain boundaries of the alloy preferentially reacted with chlorine, which resulted in a severe granular corrosion and a Cr-depleted zone. The volatilization of the chlorides gradually increased with increasing temperature, which in turn reduced the partial pressures of chlorine in the scale/substrate boundary, thereby leading a slower corrosion rate at 850 ℃. Haynes 188 contained with 14% tungsten, the oxide and chloride of tungsten that formated after NaCl hot corrosion have high volatility, caused the largely weight loss on the dynamics curve.
In addition it was found that the HA-188 alloy exhibited a better hot-corrosion resistance, as compared to those of the Fe-based steels (430SS, 304SS, 310SS, 253MA, and 353MA) under the previous studies in our laboratory. It may be concluded that the hot-corrosion resistance of the Co-based superalloy is much superior to those of Fe-based steels.

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