兩種氮含量690合金中晶界碳化物及晶界鉻貧化研究

兩種氮含量690合金中晶界碳化物及晶界鉻貧化研究RESEARCH ON THE CARBIDE PRECIPITATION AND CHROMIUM DEPLETION IN THE GRAIN BOUNDARY OF ALLOY 690 CONTAINING DIFFERENT CONTENTS OF NITROGEN

針對(duì)2 種 N含量(0.001%和0.03%, 質(zhì)量分?jǐn)?shù))的 690 合金, 采用 SEM, TEM 并結(jié)合EDS 分析等手段系統(tǒng)研究了時(shí)效處理后合金晶界碳化物和晶界附近的 Cr 貧化行為, 并定量描述了熱處理時(shí)間對(duì)晶界附近Cr 貧化程度的影響. 結(jié)果表明, 高 N 含量合金晶界析出的碳化物之間距離較大, 且碳化物尺寸較小, 隨著時(shí)效時(shí)間延長(zhǎng)碳化物逐漸長(zhǎng)大. 隨著時(shí)效時(shí)間的延長(zhǎng), 貧 Cr 區(qū)的 Cr 含量逐漸提高, 高 N 含量的 690 合金晶界附近貧 Cr區(qū)的 Cr含量高于低 N含量合金, 主要原因是晶粒細(xì)化所致.

Nickel-based alloy Inconel 690 (hereinafter called alloy 690) is currently replacing alloy 600 as steam generator tubes in pressurized water nuclear reactors, owing to its excellent resistance to intergranular stress corrosion cracking (IGSCC) and good mechanical properties. The carbide precipitation is a major microstructural characteristic during heattreatment of stainless steels and nickel-based alloys. The carbide precipitation and chromium depletion in the brain boundary of alloy 690 were investigated. The grain size and carbide of alloy 690 with 0.001% and 0.03% (mass fraction) nitrogen content were observed and analyzed. The extent of chromium depletion in the vicinity of grain boundaries was quantitatively determined as a function of thermal treatment time. The solution treatment of the samples was at 1080 ℃ for 10 min, and then the samples were thermally treated at 715 ℃ for 1~25 h. The results show that the nitrogen addition decreases the intergranular carbide density and the average carbide length but increases its distance. The level of chromium in the depleted regions in alloy 690 with 0.03%N is higher than that with 0.001%N. This is attributed to the beneficial role of nitrogen addition against grain growth and sensitization.

全文下載：http://pan.baidu.com/s/1c27xheS