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含鉬鎳基焊縫金屬在硝酸溶液中的腐蝕行為

2021-04-19 13:43:29 作者：張旭來源：材料研究學報分享至：

含鉬鎳基焊縫金屬在硝酸溶液中的腐蝕行為

張旭, 陸善平

1. 中國科學院金屬研究所沈陽材料科學國家研究中心沈陽 110016

2. 中國科學院核用材料與安全評價重點實驗室沈陽 110016

3. 中國科學技術(shù)大學材料科學與工程學院沈陽 110016

Corrosion Behavior of Ni-based Weld Metals with Different Mo Content in a Nitric Acid Aqueous Solution

ZHANG Xu, LU Shanping

1. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China

2. CAS Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China

3. School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China

摘要

研究了三種不同Mo含量的鎳基焊縫熔敷金屬在強氧化性介質(zhì)（65%硝酸溶液）中的腐蝕行為。結(jié)果表明，熔敷金屬在硝酸溶液中浸泡后發(fā)生了晶間腐蝕、點蝕以及枝晶間腐蝕等局部腐蝕。由于Mo元素促進了大尺寸Laves相在熔敷金屬枝晶間的析出，在Laves相與基體之間產(chǎn)生了較大的電化學差異，導致Laves相在氧化性介質(zhì)中腐蝕溶解，增大了熔敷金屬的點蝕敏感性。在620℃焊后的去應力退火過程中，在焊縫中發(fā)生元素再分配，Mo元素降低了枝晶間Ni、Cr元素的貧化。由于枝晶間Ni、Cr元素的貧化是引起熔敷金屬枝晶間腐蝕的重要因素，Mo元素降低了焊縫熔敷金屬在硝酸溶液中枝晶間腐蝕敏感性。

關(guān)鍵詞：材料失效與保護 ; 耐蝕性 ; ASTM-262A ; 鎳基焊縫 ; 鉬

Abstract

Welding overlayers of three welding wires containing various concentrations of Mo have been fabricated as the experimental materials via multiple semiautomatic gas tungsten arc welding （GTAW） with cold-wire feed. Then post-weld heat treatment is carried out at 620℃ for 29 h to reduce the welding residual stress. The corrosion resistance of the as-weld and heat-treated Ni-based weld metals is assessed in 65% nitric acid aqueous solution at 117℃ for 48 h. The results show that weld metals were suffered from several types of localized corrosion in the test medium, such as intergranular corrosion （IGC）， pitting corrosion and interdendritic corrosion （IDC）。 Mo can promote the precipitation of Laves phase in the interdendritic region. Due to the electrochemical difference between the Laves phases and the matrix, pitting susceptibility of the Ni-based weld metals increase with the increase of Mo content. Further, the IDC takes place in the heat-treated weld metals. The electrochemical difference between the dendrite and the interdendritic region is the key factor for IDC. Mo can influence the diffusion of Ni and Cr during the post heat treatment and decrease the depletion degree of Cr and Ni in the interdendritic zone, then the degree of IDC drops for the heat-treated weld metals with addition of Mo.

Keywords： materials failure and protection ; corrosion resistance ; ASTM-262A ; Ni-based weld metals ; Mo