Simulation of processes of high-temperature gas corrosion of titanium alloys in vacuum

Maksimovich, G. G.; Fedirko, V. М.; Pavlina, V. S.; Pichugin, A. T.; Luk’yanenko, A. G.

doi:10.1007/bf00723648

Cited by 1 publication

(2 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To construct a mathematical model of the kinetics of interaction of titanium with gaseous media under the conditions of cyclic changes in temperature, we use the equations obtained in [5,7]. Thus, in the case of saturation of the metal with a single component under low partial pressure (a monophase diffusion zone along the coordinate x, C(x, x) is a concentration, and o3 is a degree of damage), we can write If we now specify the functions appearing in relations (1) and (2), namely, the coefficients of diffusion D(to) and mass transfer h(o)), the rate of accumulation of damage tzo(o)), and the level of solubility on the boundary C o (co), then we arrive at a diffusion problem with time-dependent diffusion and mass-transfer coefficients and the boundary value of the concentration.…”

Section: Mathematical Representationmentioning

confidence: 99%

“…Numerical experiments, various models and procedures used for the numerical analysis of the kinetics of gas saturation demonstrate that the near-surface phenomena in titanium reacting with oxygen and nitrogen are quite complicated (include many stages and are governed by different mechanisms) [4][5][6]. The procedure of thermal cycling leads to the accumulation of damage (increase in the density of dislocations and vacancies, crushing of grains, etc.)…”

Section: Physical Statement Of the Problemmentioning

confidence: 99%

See 1 more Smart Citation

Effect of thermal cycling on high-temperature interaction of titanium with gases

Luk’yanenko¹,

Pavlyna²,

Pichugin³

et al. 1997

Mater Sci

Self Cite

View full text Add to dashboard Cite

We present results of complex (theoretical and experimental) investigation of the effect of thermal cycling on the kinetic regularities of diffusion and formation of phases in titanium alloys in contact with gaseous media. We emphasize the importance of conditions of mass exchange and chemical reactions on phase boundaries determining the character of growth and properties of the new phase.Thermal cycling is extensively used for the intensification of physicochemical processes in the course of chemical and thermal treatment of steels and alloys based on nickel and there exists a satisfactory scientific substantiation of its application [1][2][3]. As far as titanium and alloys based on titanium are concerned, this method is practically not used because there are no data on the characteristics of their high-temperature interaction with oxygen-and nitrogen-containing media under the conditions of cyclic changes in temperature. Physical Statement of the ProblemNumerical experiments, various models and procedures used for the numerical analysis of the kinetics of gas saturation demonstrate that the near-surface phenomena in titanium reacting with oxygen and nitrogen are quite complicated (include many stages and are governed by different mechanisms) [4][5][6]. The procedure of thermal cycling leads to the accumulation of damage (increase in the density of dislocations and vacancies, crushing of grains, etc.) and affects the conditions of contact of titanium with gaseous media including such primary phenomena as adsorption and phase-boundary reactions by changing their thermodynamic and kinetic regularities. In this case, it is reasonable to speak about the time dependence of the properties of materials and characteristics of the process of mass exchange between the material and environments. This is true independently of the partial pressure of oxygen (nitrogen). As pressure or temperature increases, it is necessary to consider two basic processes, namely, the process of formation of oxide and nitride films (mainly, in the bulk of the matrix) and the process of diffusion saturation of the metal with interstitial atoms to significant depths and quite high concentrations. As expected, thermal cycling intensifies the diffusion displacements of impurity atoms (their diffusion coefficients increase both in the matrix and in the newly-formed phase) and strongly affects the conditions of formation and growth of the new phase because the number of possible nucleation centers on the phase boundary permanently increases with time and the energy barrier of the phase transformation decreases. These effects are typical of titanium because, in iron and nickel, under similar conditions, the new phase is mainly formed as a result of the diffusion of cations. Thus, the procedure of thermal cycling leads to the formation of oxide (nitride) films with specific structure characterized by an elevated density, degree of dispersion, and deviation from the stoichiometric composition toward the deficiency of oxygen (nitrogen) accompanied by a...

show abstract

Section: Mathematical Representationmentioning

confidence: 99%

Section: Physical Statement Of the Problemmentioning

confidence: 99%