Pt-10Rh/Pt热偶在还原气氛中脆断失效分析

Research on Embrittle Failure of Platinum∶10% Rhodiun-Platinum Thermocouple in Reduction Atmosphere

试验证实了高温下Ｐｔ－ １０Ｒｈ／Ｐｔ 热偶在Ｈ２ 或ＣＯ 气氛中使用时因脆性而会很快断裂失效。采用透射电镜（ＴＥＭ） 对脆断偶丝进行微观组织和形貌观察， 定性定量研究认为：脆断失效的根本原因在于Ｓｉ 与Ｐｔ 作用形成Ｐｔ５Ｓｉ２ 低溶点共晶物， 使偶丝局部熔点降低而熔化， 发生脆断。脆断处局部区域Ｓｉ 最大含量分别达到７．９３ ％ 和３．２７ ％ ， 而Ｓｉ 是高温下耐火材料中ＳｉＯ２ 被Ｈ２ 或ＣＯ 还原产生的。

The platinum:10 percent rhodium-platinum thermocouple heated in hydrogen or carbonmonoxide become embrittled and break.The TEM observation on compositions and microstructures of failure sample has been confirmed that the low melting point eutectic Pt 5Si 2 segregated on the grain bondaries causes embrittle failure.The silicon content in the melting microarea is 7 93 percent and 3 27 percent separately.The silicon comes from silica-containing refractories in reduction condition.