純鎳及鎳基超合金在600℃之高溫硫化腐蝕研究

The High-Temperature Sulfidation of Pure Nickel and Nickel-base Superalloys at 600℃

本研究在探討純鎳及四式鎳基超合金（含Inconel 600，690，718及738合金）在溫度600℃，純硫分壓Ps2=104 Pa下之高溫硫化行為。結果顯示，純鎳及所有鎳基超合金的腐蝕動力學皆遵守拋物線型定律，且其腐蝕反應速率因合金的種類而異，以Inconel 738的抗硫化性能最佳，約比純鎳慢四個數量級。純鎳硫化後生成單一的硫化鎳（NiS），而由於鎳基超合金的組成成份相當多，在高溫硫化下則生成內、外兩層複雜的硫化物。所有鎳基超合金之外層主要為硫化鎳（NiS），且Inconel 738另有少量的硫化鈷（CoS2）生成，而內層為混合的硫化物如In-600及In -690生成有硫化鎳（NiS）及硫化鉻（Cr2S3/Cr3S4）其中，硫化鉻在In-690中生成量遠及多於In-600，而In-718生成有NiS及微量的硫化鐵（Fe1-xS）與硫化鉻（Cr5S6），而In-738主要包括硫化鎳（NiS）及微量的硫化鈷鎳（CoNi2S4）。

The purpose of the research is to study the high-temperature sulfidation behavior of pure nickel and 4 nickel-base superalloys(containing Inconel 600, 690, 718, and 738 alloys) at 600℃ in a pure sulfur pool of Ps2=104 Pa. The corrosion kinetics followed the parabolic rate law. and the corrosion rates are strongly dependent on alloy compositions. The scales formed on the alloy were complex, consisting of the outer and the inner layers. The outer scales of nickel-base superalloys formed at 600cc consisted of mostly nickel sulfide (NiS) and minor cobalt sulfides (CoS2)(only detected on In-738). The inner layer of In-600 and In-690 was a heterophasic mixture of nickel sulfide (NiS) and a few chromium sulfides (Cr2S3/Cr3S4) whose amounts are signiticantly abundant in the In-690 alloy, that of In-718 was a heterophasic mixture of nickel sulfide (NiS), a few iron sulfides (Fe1-xS) and chromium sulfides (Cr5S6), and that of In-738 was a heterophasic mixture of nickel sulfide (NiS) and a few cobalt-nickel sulfides (CoNi2S4).