Cyclic strength of steel 16Kh3NVFBM-Sh (VKS-5) after vacuum carburizing

Computational Evaluation of Cyclic Strength of Carburized Gears from Heat-Resistant Steels

“…In accordance with the experimental results obtained in [14], the range of carbon concentration from 0.85 to 1.05% corresponds to that of the highest computed values of the bending fatigue limit.…”

“…The values of the fatigue limit in the diffusion layer after carburizing by regimes 1 and 2 computed with the help of these results by formula (1) also differed substantially from the experimental results of [14] (see Table 1). The fatigue value computed by this method after carburizing by regime 2 exceeded the corresponding experimental value by about a factor of 1.5, which is absolutely unsatisfactory.…”

“…It should be noted that the model is not applicable to computing the fatigue value in oxidizing gas atmospheres, because the decarburization developed in this case is accompanied by precipitation of acicular oxide particles characterized by much higher stress concentration factors than those of carbides and hence by considerably lower values of the fatigue limit as compared to those computed by the model suggested [14]. Notations: t a is the duration of the active stage; t p is the duration of the passive stage; C C is the carbon concentration on the surface; h eff is the effective thickness of the layer; s -1(bend) is the bending fatigue limit.…”

“…This value cannot be underestimated, because it follows from an elementary computation by formula (5) that at a 20% volume fraction of cementite the integral coefficient of stress concentration K k = 0.88. After the amendment performed for checking the adequacy of the model developed, we computed the bending fatigue limit for two symmetrical regimes of vacuum carburizing, the experimental values of s -1 for which had been obtained in [14]. A preliminary computation of the parameters of the diffusion layer required for computing the fatigue limit by formula (4) was made by the method of [6,7].…”

Magnetic Evaluation of the Structural and Phase Changes in Individual Layers of Multilayer Products

“…/ Magnetic evaluation of the structural and phase changes in individual layers of multilayer products глубине от 0,5 до 1,2 мм с твердостью от 500 до 250 HV и градиентной структурой, переходя-щей от сорбита с прослойками избыточного цементита и включениями остаточного аустенита к феррито-перлитной сердцевине. Пониженная твердость поверхностного слоя глубиной до 0,1 мм объясняется обезуглероживанием и окислением тонкого поверхностного слоя при газо-вой цементации [14]. Внутреннее окисление считается неустранимым дефектом, но вследствие проникновения на небольшую глубину он может быть удален при шлифовке [15].…”