Research on Hydrogen Induced Cracking of 08Cr2AlMo Steel Based on the Empirical Electron Theory

Abstract

Hydrogen induced cracking (HIC) is one of main type of damage to metallic materials in H2S solution. 08Cr2AlMo steel is a type of material developed especially for heat exchanger pipe bundle used under H2S condition in recent years. Calculation models of the construction units in 08Cr2AlMo steel with or without hydrogen were established based on the empirical electronic theory in solid (EET) and valence electron structure of the construction units in this steel was calculated. The results show that hydrogen bond is formed between the hydrogen solved in the steel and other atoms in the steel. The cleavage energy of crystal plane with hydrogen bond is increased and that without hydrogen bond is decreased. Hydrogen results in the remarkable difference of the cleavage energy of different crystal planes and changes the bond distribution in the structure units. The mechanical property of the units has directional properties. In these units, the microcracks propagate along the cleavage plane with small binding energy and so the brittle fracture of the crystal occurs. The elements of Cr, Al, Mo are able to strengthen the basal body without carbon, and have little effect on the plastic nature. In the structure unit with carbon, carbon increases the anisotropy of mechanical property and alloying agents decrease the plastics of the steel further. The alloying agents of Cr and Mo decrease plastic nature loss of the steel due to decrement of the anisotropy of mechanical property in the unit with hydrogen. The alloying agent of Al has little effect on the loss of plastic nature.