tailieunhanh - Material Science_ Vol 1 of 2 - US DOE (1993) WW Part 12

Tham khảo tài liệu 'material science_ vol 1 of 2 - us doe (1993) ww part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Properties of Metals DOE-HDBK-1017 1-93 CORROSION HYDROGEN EMBRITTLEMENT Personnel need to be aware of the conditions for hydrogen embrittlement and its formation process when selecting materials for a reactor plant. This chapter discusses the sources of hydrogen and the characteristics for the formation of hydrogen embrittlement. EO DESCRIBE hydrogen embrittlement including the two required conditions and the formation process. EO IDENTIFY why zircaloy-4 is less susceptible to hydrogen embrittlement than zircaloy-2. Concern Another form of stress-corrosion cracking is hydrogen embrittlement. Although embrittlement of materials takes many forms hydrogen embrittlement in high strength steels has the most devastating effect because of the catastrophic nature of the fractures when they occur. Hydrogen embrittlement is the process by which steel loses its ductility and strength due to tiny cracks that result from the internal pressure of hydrogen H2 or methane gas CH4 which forms at the grain boundaries. In zirconium alloys hydrogen embrittlement is caused by zirconium hydriding. At nuclear reactor facilities the term hydrogen embrittlement generally refers to the embrittlement of zirconium alloys caused by zirconium hydriding. Sources of Hydrogen Sources of hydrogen causing embrittlement have been encountered in the making of steel in processing parts in welding in storage or containment of hydrogen gas and related to hydrogen as a contaminant in the environment that is often a by-product of general corrosion. It is the latter that concerns the nuclear industry. Hydrogen may be produced by corrosion reactions such as rusting cathodic protection and electroplating. Hydrogen may also be added to reactor coolant to remove oxygen from reactor coolant systems. Hygrogen Embrittlement of Stainless steel As shown in Figure 10 hydrogen diffuses along the grain boundaries and combines with the carbon C which is alloyed with the iron to form methane gas. The methane .