Study on the Hydrogen Effect on the Temper Embrittlement of 2.25Cr-1Mo Steel

2010 ◽  
Author(s):  
Xiliang Zhang ◽  
Changyu Zhou
Keyword(s):  
Hydrogen Embrittlement ◽  
Grain Boundary ◽  
Boundary Segregation ◽  
Temper Embrittlement ◽  
Grain Boundary Segregation ◽  
Hydrogen Effect ◽  
Electron Spectrometer ◽  
Boundary Concentration ◽  
Theory Calculation ◽  
The Relationship

The relationship between hydrogen embrittlement and temper embrittlement of 2.25Cr-1Mo steel was investigated by Auger electron spectrometer testing and electrochemical hydrogen charging. The results indicate that atomic hydrogen increases the grain boundary concentration of impurity element P and temper embrittlement. The increscent temper embrittlement degree by hydrogen will rise with further embrittlement and the relationship between increscent temper embrittlement degree and temper embrittlement degree is ΔCp = log[4.9351×(Cp)1.31687]. The grain boundary segregation theory was used and results of theory calculation and testing show that the relationship between hydrogen embrittlement and temper embrittlement can be explained by theory of grain boundary segregation. The embrittlement degree of 2.25Cr-1Mo steel which is induced by hydrogen and temper embrittlement is Cp′ = log[4.9351×(Cp)1.31687]+Cp.

Influence of Phosphorus Grain Boundary Segregation on Fracture Behaviour of Iron-Base Alloys

2007 ◽  
Vol 567-568 ◽  
pp. 33-38
Author(s):  
Jozef Janovec ◽  
Jaroslav Pokluda ◽  
Pavel Lejček
Keyword(s):  
Grain Boundary ◽  
Intergranular Fracture ◽  
Stainless Steels ◽  
Structural Changes ◽  
Fracture Behaviour ◽  
Boundary Segregation ◽  
Austenitic Stainless Steels ◽  
Grain Boundary Segregation ◽  
Boundary Concentration ◽  
Factors Influencing

Chemical and structural changes at the grain boundaries were investigated to quantify their influence on fracture behaviour of austenitic stainless steels and model ferritic Fe-Si-P alloys. The balance between the size and the area density of intergranular particles was found to be one of the most decisive factors influencing sensitivity of the steels to intergranular fracture. The precise dependence of the energy of intergranular fracture on the phosphorus grain boundary concentration was also determined.

Effect of Isothermal Holding Temperature on NGS Kinetics of Phosphorus and Temper Embrittlement

2007 ◽  
Vol 348-349 ◽  
pp. 549-552
Author(s):  
Jun Wang ◽  
Qing Fen Li ◽  
Er Bao Liu
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Isothermal Holding ◽  
Boundary Segregation ◽  
Temper Embrittlement ◽  
Solution Treatment ◽  
Grain Boundary Segregation ◽  
Solution Temperature ◽  
Kinetics Of ◽  
Holding Temperature

When failure occurs in material, it is often occurs by fracture along some grain boundaries and often by the micro-segregation of embrittling impurity to the grain boundaries. In the present work, the non-equilibrium grain-boundary segregation (NGS) kinetics of phosphorus and the temper embrittlement at the same solution treatment and different isothermal holding temperature in steel 2.25Cr1Mo are studied. The NGS kinetics curves of phosphorus at the same solution temperature （1050 oC ）and different isothermal holding temperature (540 oC and 600 oC) are given. Experimental results provide a direct evidence of NGS kinetic model and show that the grain boundary segregation concentrations of phosphorus for specimen isothermal holding at 540 oC are higher than those at 600 oC. The peak values of AES patterns of solute atoms for specimen isothermal holding at 540 oC are also higher than those at 600 oC. It is therefore concluded that the lower the isothermal holding temperature, the higher the segregation concentration of phosphorus at the grain-boundaries, and also the higher the degree of embrittlement.

Grain Boundary Segregation Versus Precipitation in Grains. Effect on Diffusion

2005 ◽  
Vol 237-240 ◽  
pp. 502-511 ◽  
Author(s):  
Boris S. Bokstein ◽  
A.N. Smirnov
Keyword(s):  
Fracture Surface ◽  
Grain Boundary ◽  
Binary Systems ◽  
Boundary Segregation ◽  
Atomic Layer ◽  
Solute Concentration ◽  
Grain Boundary Segregation ◽  
Interatomic Distances ◽  
Boundary Concentration ◽  
Solute Atoms

Thermodynamic model is developed of which it follows that saturation value of solute segregated in grain boundary, provided all available sites occupied, must be close to the solute concentration, in the nearest in composition phase in grain as it follows from phase diagram. Based on the analysis of experimental data for three binary systems (Cu –Sb, Fe – P and Fe – Sn) it is shown that the surplus concentration of the solute atoms in GB as compared with a concentration in grain is distributed equally between two fracture surfaces but takes up more than one atomic layer. The thickness of the segregation region (with surplus concentration in grain boundary) averages usually from 3 to 6 interatomic distances. As a rule, solute distribution is symmetrical on each side of the fracture surface. It is shown that maximum of grain boundary concentration falls on the first layer on the fracture surface. The method is developed of the calculation of the first layer concentration. It is shown that this concentration is close to the solute concentration in the nearest in composition phase in grain.

Experimental Studies of Non-Equilibrium Grain-Boundary Segregations of Phosphorus under Low Tensile Stresses

2007 ◽  
Vol 353-358 ◽  
pp. 396-399
Author(s):  
Yu Dong Fu ◽  
Gang Wang ◽  
Chen Liu ◽  
Qing Fen Li
Keyword(s):  
Grain Boundary ◽  
Experimental Studies ◽  
Boundary Segregation ◽  
Critical Time ◽  
Grain Boundary Segregation ◽  
Low Alloy Steels ◽  
Different Temperatures ◽  
Alloy Steels ◽  
The Relationship ◽  
Non Equilibrium

In the present paper, the non-equilibrium grain-boundary segregation of P atom was studied in low alloy steels subjected to a low tensile stress at different temperatures. The AES (Auger electron spectroscopy) experiments and dynamic analyses were conducted to study on the non-equilibrium grain-boundary segregation of P atom. The research results show that non-equilibrium segregation of phosphorus occurred at the grain boundaries of the steels 2.25Cr1Mo and 12Cr1MoV, while the critical time reached about 0-1 hour at constant temperatures 773 and 813K. The relationship between the diffusion rate and the diffusion time for the complex and the phosphorus atom was investigated based on the experimental results. Eventually the diffusion coefficients of complex and P were calculated with using a proposed dynamic model.

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