V. E. Gromov

Increase in the fatigue durability of stainless steel by electron-beam surface treatment

The structure, phase composition and dislocation substructure of 20Cr23Ni18 steel subjected to electron-beam treatment and subsequent multicycle fatigue loading until destruction were studied by scanning and transmission electron microscopy. It was shown that electron-beam treatment with an energy density of 20 J/cm2 increases the fatigue durability by a factor of 2.1. The cause of steel fatigue destruction is analyzed and a way of further increasing the fatigue durability is proposed.

Evolution of the phase composition and defect substructure of rail steel subjected to high-intensity electron-beam treatment

The morphology, structure-phase states, and defect substructure of annealed rail steel subjected to electron-beam treatment in the surface-layer melting mode are studied by scanning and transmission electron microscopy methods. The formation of the lath martensite structure, as well as cellular and dendritelike structures, containing nanoscale martensite crystals, is revealed.

Structural-phase states and properties of coatings welded onto steel surfaces using powder wires

Structural-phase states and mechanical properties of coatings welded onto Hardox 400 steel using En-DOtecDO*30, EnDOtecDOtec*33, and SK A 70-G weld wires are investigated via X-ray structural analysis, optical and scanning electron microscopy, and measuring microhardness, wear resistance, and friction coefficients. It is shown that the coatings had microhardnesses and wear resistances were higher than those of their substrate by factors of 2–3 and 2, respectively, while the friction coefficients of coatings were lower than those of the substrates by a factor of 1.2. Hardening was due to the formation of disperse structures containing up to 40 vol % of Fe3C, Fe23(C, B)6, NbC, Fe3B, and Fe3Si0.97 particles.

Formation of surface gradient structural-phase states under electron-beam treatment of stainless steel

The structural-phase states of steel 08X18H10T (0.08% C, 18% Cr, 10% Ni, 1% Ti) subjected to pulse electron beam treatment in the regime of surface layer melting is investigated using the methods of optical and electron microscopy. The regularities of variations in the phase composition and the state of the defect substructure moving away from the irradiation surface up to a 200-μm depth are revealed.

Evolution of the structure and phase states of rails in prolonged operation

The transformation of the structural and phase states and defect substructure of the surface layer (depth up to 10 mm) in rails during prolonged operation (with a total load amounting to 1000 million t) is analyzed on the basis of metal physics. The microhardness is plotted, and decrease in strength of the rail’s contact surface after prolonged operation is noted. In rail operation, a multilayer structure is formed. The surface layer (about 20 μm) has a multiphase submicrocrystalline and nanocrystalline structure; it contains micropores and microcracks. The structure at a distance of 2 mm from the contact surface is morphologically similar to the steel structure before operation: it consists primarily of pearlite grains (mainly plates), mixed ferrite-carbide grains, and structure-free ferrite grains. The density of the flexural extinction contours increases at a distance of 2 mm from the contact surface. The amplitude of the stress field is greatest at the phase boundary between a globular particle and the matrix.

Surface relief and structure of electroexplosive composite surface layers of the molybdenum-copper system

The surface topography and structure of copper layers exposed to multiphase plasma jets of products of electrical explosion of molybdenum and copper foils are studied using profilometry and scanning electron and light microscopy. Such treatment allows deposition of either layered coatings or alloyed composite layers. It is found that the surface layer roughness parameter is Ra = 3.2−4.0 μm. The thickness of some copper and molybdenum layers of coatings is 15–20 μm. Electroexplosive alloying produces layers 25 μm thick. Sizes of copper inclusions in the molybdenum matrix near the surface of such layers vary from 30 nm to 1–2 μm.

Evolution of Al–19·4Si alloy surface structure after electron beam treatment and high cycle fatigue

Abstract Processing of Al–19·4Si alloy by high intensive electron beam has been carried out, and multiple increase in fatigue life of the material has been revealed. Investigations of structure and surface modified layer destruction of Al–19·4Si alloy subjected to high cycle fatigue tests to fracture have been carried out by methods of scanning electron microscopy. The factors responsible for the increase in fatigue life of Al–19·4Si alloy have been revealed and analysed.

Surface layer structure degradation of rails in prolonged operation

By methods of optical, scanning and transmission electron microscopy and microhardness measurement the transformation regularities of structure-phase states, defect substructure, fracture surface and mechanical properties of rail surface layer up to 10 mm deep in process of long-term operation (passed tonnage of gross weight 1000 mln. tons) were revealed. According to the character of fracture and level of structure imperfection the three layers were detected: surface, transition and boundary ones. It has been shown that the surface layer ~20 μm in thickness has a multiphase, submicro- and nanocrystalline structure and it contains micropores and microcracks. The increased density of bend extinction contours at 2 mm depth from the tread contact surface was noted, and it was shown that the maximum amplitude of stress fields was formed on the interphase boundary the globular cementite particle–matrix. The evaluation of stress fields was done.

On the influence of the electrical potential on the creep rate of aluminum

The influence of the electrical potential on the creep rate of aluminum is studied experimentally. The effect of the electrical potential applied to the sample is compared with the effect of the potential induced by the contact potential difference upon contact with seven different metals characterized by different work functions. It is revealed that these two types of electrical effects are qualitative equivalent to each other.

Structure gradient in wear-resistant coatings on steel

As shown by scanning electron microscopy, electric-arc surfacing of steel produces a multilayer structure, including the surface coating itself, a transition layer, and a thermal-influence zone. Solidification of the coating is accompanied by the formation of a columnar structure, with alternating layers (thickness 8–10 μm) of two types. The first type is characterized by plate structure, oriented perpendicular to the substrate surface; the thickness of the plates and the interlayers between them is 50–100 nm. The second type has plate and globular structure. On moving away from the surface, the plate structure of the first type breaks down; none remains at the boundary with the transition layer. The globules measure 1.5–3.0 μm; they are fragmented. The structure gradient is also apparent in the transition layer and in the thermal-influence zone. The boundary between the coating and the steel is in an elastic stress state on account of the superhigh heating and cooling rates, as indicated by the presence of microcracks, micropores (in rows), and extended secondaryphase layers.