Efficiency Of Hardening Research Articles

Physicochemical Properties of Carbonitrided 40Kh Steel

We present the results of investigations of the influence of hydrogen-free carbonitriding in glow discharge on the physicochemical characteristics of the hardened layer of 40Kh steel depending on the content of propane and the pressure of gas atmosphere. We consider three versions of saturation: carbon + nitrogen, nitrogen + carbon, and simultaneous saturation with nitrogen and carbon. The analysis of the obtained results reveals the highest efficiency of hardening of the surface of 40Kh steel for the third version of saturation.

Long-term strength of an elastic body with elliptic crack filled with a viscoelastic material

We obtain the solution of the problem of limiting state of an elastic body containing an elliptic crack filled with a viscoelastic material. The parameters of the problem specifying the efficiency of hardening of the body by filling the defects with injection materials are determined. For the filler material with rheological properties of the Kelvin substance, the required solution is obtained in the closed analytic form.

Mechanism of surface hardening of structural carbon steels

Results of fatigue tests of steel specimens with different carbon contents are presented. We propose a dislocation model of strength of a two-phase plastically deformed body, according to which the formula for the assessment of the efficiency of hardening and the increase in the fatigue resistance of carbon steels is corrected.

Mechanical, electrochemical and tribological properties of nanocrystalline surface of brass produced by sandblasting and annealing

Mechanical, electrochemical and tribological properties of nanocrystalline surfaces of a brass alloy (70–30) produced by sandblasting and annealing were investigated. The grain size of a nanocrystalline surface was determined by means of optical microscopy and transmission electron microscopy. The relationships between the grain size of a surface and its properties were investigated using nano-/micro-indentation, micro-scratch, electrochemical scratch and polarization techniques. It was demonstrated that the surface hardness and elastic behavior were improved as the grain size decreased, leading to markedly enhanced wear resistance. The efficiency of hardening by reduction of grain size became lower in the nanocrystalline region, compared to that in the microcrystalline region. The potentiodynamic polarization test indicated that the nanocrystalline surface had higher resistance to corrosion. Nano-indentation and micro-scratch test with in situ monitoring changes in contact electrical resistance demonstrated that the nanocrystallization was significantly beneficial to the mechanical behavior of the passive film. Mechanisms responsible for the beneficial effects of nanocrystallization on properties of brass and its passive films are briefly discussed.

Efficiency Of Surface Cold-work Hardening Of Titanium AlloysHaving Different Phase Composition

The characteristic features of influence of preliminary plastic deformation degree (E ') on endurance limit (G.,) of titanium alloys having different phase composition are revealed. The connection between character of relation (G., - E ') and efficiency of hardening of parts by methods of surface plastic deformation (SPD) is shown. On the basis of the analysis of investigations of a, pseudo-a, and a, + P titanium alloys a conclusion is confirmed experimentally that the absence of sharp decrease of endurance limit of a material in the field of minimum plastic deformations makes hardening of parts by methods of SPD effective. It is shown. that the realization of tests on the base of 10' cycles of loading is sufficient for study of change of resistance to fatigue of titanium alloys under influence of preliminary plastic deformation, while the results of these investigations allow to predict effect of decrease of endurance limit of subjected to SPD parts, which reveals itself only at increase of test base up to from 10' to 10' cycles of loading.

Mechanical and Corrosion Characteristics of Zr + 2.5% Nb Zirconium Reactor Alloy

The results of structural and phase hardening of pipes made of Zr + 2.5% Nb alloy show that ultrahigh-frequency thermal treatment of pipes (fast heating to the temperature of existence of the β-phase followed by sharp cooling and annealing in the high-temperature range of the α-phase) destroys the texture and forms a fine-grained structure (the grain diameter is about 1 μm) with numerous transitional twins and a high density of precipitations of the secondary β-niobium phase (∼ 1016 cm−3). In this state, the alloy is rather strong and plastic (at room temperature, σu ≈ 650 MPa, σ0.2 ≈ 550 MPa, and δ ∼ 20% both in the longitudinal and transverse directions). The efficiency of hardening by ultrahigh-frequency thermal treatment is not reduced with increase in the temperature of testing up to 500°C. Corrosion tests of channel pipes made of Zr + 2.5% Nb alloy subjected to ultrahigh-frequency thermal treatment in water containing various amounts of oxygen (from 0.1–0.3 to 600 mg/kg) at temperatures of 285–350°C for 700–6600 h under static conditions and in reactor water of the Ignalina Nuclear Power Plant for ∼ 5000 h under dynamic conditions showed that the corrosion resistance of this alloy is on a par with the corrosion resistance of the material of assembly channels of high-power channel reactors subjected to a standard treatment.

Efficiency of hardening by surface plastic deformation of underhub parts of shafts with partial removal of the cold worked layer

Efficiency of hardening by surface plastic deformation of underhub parts of shafts with partial removal of the cold worked layer

Kinetics of ultrasonic hardening

1. The processes that occur during ultrasonic treatment up to the beginning of failure of the material are characterized by general relationships and include several stages: 1a) A stage of constant hardness or slight reduction of the hardness, depending on the treatment conditions, which is due to breakaway of dislocations from impurity atoms pinning them (incubation period of the treatment); 1b) A stage of continuous increase in hardness associated with formation of dislocation networks under the influence of the ultrasonic treatment (the stage of ultrasonic hardening); 1c) A stage of localization of the effects of additional ultrasonic deformation in boundary areas of grains, characterized by the effects of intergranular slip and formation of pores and cracks in grain boundaries (stage of intergranular fracture). 2. The rate of hardening during ultrasonic treatment is described by a mathermatical relationship and is determined by such structurally sensitive parameters of the treatment as the length of the incubation period and the efficiency of hardening. 3. There is a correlation between the parameters of ultrasonic hardening and the initial recrystallization temperatures of metals.