Oxidation - Nitridation of Ni-Cr-Al alloys
Oxidation - Nitridation of Ni-Cr-Al alloys
复制标题
Ni-Cr-Al合金的氧化-氮化
DOI：
10.1590/s1516-14392004000100003
复制
发表时间：
2004
影响因子：
1.7
通讯作者：
D. Young
中科院分区：
文献类型：
--
作者：
Susan S. Han;D. Young
一系列含24-36wt%Cr和13.5-25.0wt%Al的合金在1100℃下与空气反应260小时，等温反应产物为α-Al_2O_3的鳞片和少量的Cr2O_3。它们按照抛物线动力学生长，并被部分层裂造成的间歇性重量损失所打断。在等温暴露过程中未发生氮化反应。在长达260个1小时循环的热循环中，反应要严重得多。反复的鳞片剥落导致铝和铬的亚表面合金耗尽，程度较小。这导致了原有的合金三相结构(a-Cr+b-NiAl+g-Ni)向单相g-Ni溶液的转变。外部氧化膜的破坏使气体能够接触到这种能够溶解氧气和氮气的金属。这两种氧化剂的向内扩散导致了复杂的内部析出区的形成：在表层以下形成了一个复杂的内部析出区：Al_2O_3和Cr2O_3，然后是Al_2O_3，然后是AIN，然后是AIN+和Cr2N，最后在最深的区域只有AIN。扩散控制的动力学最初是有效的，但对内部沉淀区的机械破坏导致了更快的气体获取和长期近似的线性动力学。
A series of alloys containing 24-36 wt pct Cr and 13.5 - 25.0 wt pct Al was reacted with air at 1100°C for 260 h. The products of isothermal reaction were scales of a-Al2O3 plus small amounts of Cr2O3. These grew according to parabolic kinetics, interrupted by episodic weight losses caused by partial spallation. No nitridation occurred during the isothermal exposures. Reaction during thermal cycling for up to 260 one hour cycles was much more severe. Repeated scale spallation led to subsurface alloy depletion in aluminium and, to a lesser extent, chromium. This caused transformation of the prior alloy three-phase structures (a-Cr+b-NiAl+g-Ni) to single-phase g-nickel solution. Destruction of the external scale allowed gas access to this metal which was able to dissolve both oxygen and nitrogen. Inward diffusion of the two oxidants led to development of a complex internal precipitation zone: Al2O3 and Cr2O3 beneath the surface, then Al2O3 then AIN, then AIN + Cr2N and finally AIN alone in the deepest region. Diffusion-controlled kinetics were in effect initially, but mechanical damage to the internal precipitation zone led to more rapid gas access and approximately linear kinetics in the long term.