SiC-Based Composite Materials Obtained by Siliconizing Carbon Matrices

The results of a direct numerical simulation are presented which describe the specific process of a porous medium high-temperature siliconizing. The calculations were performed taking into account the diffusion, the weak pressure gradient across a workpiece and the heat release during the condensation of gaseous silicon in pores. Phenomenological formulas for the evaporation and condensation coefficients in dependence on temperature are offered. An evolutionary equation for the temperature distribution in a sample is derived, which takes into account these processes. Mathematical statement of the problem is based on the modified MIM-model with addition Darcy’s law. Numerical modeling has been fulfilled by the finite difference method using an explicit scheme. It is shown that the heating release in the sample slows down the process of particle settling. The results of numerical simulation are consistent qualitatively with known experimental data.

Section: Introductionmentioning

confidence: 99%

The influence of heat release on the dynamics of a porous material saturation in the course of gaseous silicon condensation

Demin

Maryshev²,

Menshikov³

2022

“…A lot of works is devoted to research in the field of siliconization of metals [1][2][3][4][5][6][7][8][9][10]. Analyzing the failures of tubular furnaces of oil refining and petrochemical industries, it can be concluded that the main reason for their failure is coking and carburization of the internal surface of furnace coils.…”

Section: Introductionmentioning

confidence: 99%

Formation of silicated layer of austenitic pipe steel with different pipe sizes

Рубцов

Shermatov

Khabibullin

et al. 2022

Tubular furnaces of hazardous production facilities are unique technical devices, and serve for open fire heating of various process media to relatively high temperatures. Some of the furnaces, such as pyrolysis furnaces, hydrogen conversions are also reactors that serve to decompose the hydrocarbon feedstock into separate components. The most important element of the structure is a tubular coil. The effect of high temperatures and working media on the coil metal inevitably leads to metal degradation by forming various defects, changing the structure and mechanical properties for the worse. One of the most unfavorable moments is considered saturation of the surface layers of the metal with carbon or another - carburization of the metal. When the metal is carburized, its embrittlement occurs and the probability of brittle destruction increases. All this can lead to frequent shutdown of furnaces for repairs and significant costs. One way to contain the active diffusion of carbon into the metal may be to silicate the surface of the coil elements using different silicating mixtures, since silicon can effectively delay carbon incorporation. In this work, studies are carried out on the peculiarities of the formation of a silicated layer in fragments of pipes with dimensions of 160x6 mm, 32x2 mm, 57x4 mm made of steel 08Kh18N10T depending on the holding time in the silicating mixture.

“…All of the above causes an emergency and premature shutdown of the reaction furnace. One possible and inexpensive solution to this problem is the use of special thermodiffusion coatings based on silicon -silication [1][2][3][4][5][6][7][8][9][10]. Since silicon has a minimal chemical affinity for carbon, it should serve as an effective barrier to the diffusion of carbon into the metal in one case, and in another case, to slow down the effects of iron as a catalyst for coke formation.…”

Section: Introductionmentioning

confidence: 99%

Features of siliconizing of pipe steel X12CrNi25-20 with various term of operation in the conditions of the reactionary furnace

Рубцов

Shermatov

Seitzhaparov

et al. 2022

Most refinery and petrochemical reaction furnaces are operated under harsh conditions characterized by high pressures, temperature, and aggressiveness of the process environment. The high temperature and features of the heated raw material contribute to the formation and deposition of coke on the surface of the furnace pipes, which through adhesion and diffusion phenomena has a negative effect and reduces the operational reliability of the entire furnace, causing such a negative phenomenon as carburization of the metal. Carburization contributes to a significant limitation of the ductility of the metal and increases brittleness, which leads to the formation of various unacceptable defects, in particular the formation of brittle cracks. The occurrence of defects of this type inevitably leads to the depressurization of the coil and, as a result, to the occurrence of emergency situations and emergency shutdown for repair. The problem of carburizing a metal can help solve the silicization of its surface layers, since silicon can serve as an effective protection for active saturation of the metal with carbon. In this regard, a relevant topic is the study of the features of the formation of a modified silicon-based surface layer in the coil tubes of a reaction furnace of steel X12CrNi25-20 with a different operating life in order to increase the reliability and reliability of the furnace during operation.