Growth stresses processes

Boron fibers, like any CVD fiber, have inherent residual stresses which originate in the process of chemical vapor deposition. Growth stresses in the nodules of boron, stresses induced due to diffusion of boron into the W core, and stresses generated due to the difference in the coefficient of expansion of the deposited boron and the tungsten boride core, all contribute to the residual stresses, and thus can have a considerable influence on the fiber mechanical properties. 

Figure 18. Schematic of protein kinase C targeted proteins. Protein kinase C serves important physiological role in cellular response to stress, growth, inflammatory processes and contractile function.

Stresses can, of course, result from an applied load on the component undergoing oxidation. However, additional stresses are generated by the oxidation process. These are growth stresses, which develop during the isothermal formation of the scale, and thermal stresses, which arise from differential thermal expansion or contraction between the alloy substrate and the scale. 

Residual film stress (film formation) The residual compressive or tensile stress in a film that results from the growth process (growth stress), phase change, and/or differences in the coefficients of thermal expansion of the film and substrate (thermal stress). Not a function of film thickness. Can vary through the thickness of the film and be anisotropic with direction in the film. See also Total film stress. 

Thus, the growth of an external oxide scale by the reaction between a pure metal or a metallic alloy and a gaseous or liquid oxidant phase at high temperature is also a combination of diffusion processes and interfacial reactions, and Fig. 2.1 also applies to such corrosion processes that are formally similar to solid-state reactions in poly-phase and multi-constituent systems. Such a similarity will be considered to extend the treatment of the Kirkendall effect for two-phase diffusion couples to the growth of an oxide scale on a pure metal or on an alloy. The roles of interfaces will be analysed more particularly in relation to some specific topics related to oxide scaling processes such as interface displacement, growth stresses and injection of point defects (vacancy or interstitial). 

Interfacial processes and growth stresses in scale growth... 

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