Papers by Keyword: Surface Strengthening

Abstract: The current article provides the results of the study on the improving the procedure of induction heating of products with a curvilinear surface profile by hardening of steam turbine blades surface with a complex helical shape and requiring protection against erosive wear [9, 10] using a universal microwave heating device. A principally new device that uses the effect of the magnetic field's force action has been developed and constructed. That makes possible to provide a high-quality strengthening of product surfaces regardless of their geometric configuration and size. The advantages of thermal treatment technology on such device are substantiated based on the results of metallographic, X-ray structural, and hardness analysis.

Abstract: The operational characteristics of metal components are often determined by the status of surface. In mechanical loading of solid bodies, the impact of the surface properties on formation and spreading of surface cracks is obvious, mainly as regards cyclic loading. Therefore, it is important to pay attention to knowledge of surface properties and their improvement.Cold plastic deformation is the easiest way to change the mechanical properties of the materials. The possibility of surface strengthening by ball or roller burnishing was found 80 years ago and since then has spread mainly into engineering and the automotive industry.In the authors’ workplace, experiments for surface layer hardening without ultrasound were realized with a newly developed device where the compressive force was applied statically, not dynamically. In the experimental part, we focused on the status of surface layers, especially the microstructure, hardness and roughness.

Abstract: By means of Ultrasonic shot peening (USSP), a strengthening surface layer was formed on Ti-6Al-4V. The polarization curves with different treatment times were investigated in 3.5% NaCl. The type of semiconductor for passivation film of 30 min treatment was measured by Mott-Schottky curve, and the thickness of the passivation film was calculated.The result of the polarization curves show that the corrosion resistance of the USSP treatment samples is increased by comparing with the untreated sample. Mott-Schottky curve of 30 min USSP treatment sample show that the passive film belongs to n-type semiconductor. The thickness of the passive film is much thicker than the untreated sample. The charge carrier density is smaller than that of untreated sample. These indicate that the surface strengthening improves the corrosion resistance of the Ti-6Al-4V in 3.5% NaCl by forming stable passive film.

Abstract: The cyclic load number of aero-engine blade during its service life is very likely beyond 107, which is regarded as the conventional fatigue limit. Moreover, surface strengthening is very often used in the manufacturing process of blade. The conventional testing method in the VHCF regime cannot exactly reflect the stress state of the blade, including the mechanism of crack initiation. To study the fatigue behavior and effects of laser shock peening, a kind of bending fatigue subcomponent specimen was designed and the laser shock peening model was established. Experiment about TC17 was accomplished by the Ulra-High Cycle bending fatigue system. It is found that the fatigue damage occurs beneath the surface and the S-N curve is continuously rather than multi-step declining in the VHCF regime. Process of surface strengthening has a significant effect on fatigue performance of TC17 titanium alloy.

Abstract: The experiment of laser cladding on the surface of 20 steel was made. The mixed powder of cobalt-based alloy powder (Co55) and tungsten powder was used as cladding material. There were three kinds of weight percent of tungsten powder, 5%, 10% and 15%. The microstructure and hardness of three kinds of laser cladding layer were studied. The microstructure of cladding zone was greatly refined after adding tungsten powder to Co55 powder. When the proportion of tungsten powder was 5%, the cladding zone was made up of dendritic crystal. The average hardness of cladding zone was 590 HV0.2. When the proportion of tungsten powder rose to 10%, there was reticular secondary carbide precipitating along the grain boundary. The average hardness of cladding zone was 648 HV0.2. When the proportion of tungsten powder rose to 15%, much granular carbide would diffusely distribute in Ni-based solid solution. The average hardness of cladding zone was 831 HV0.2.

Abstract: EDM Surface Strengthening TC4 titanium alloy is a kind of very effective surface strengthen method, and its development prospect is very considerable. The medium in the discharge process has characteristic of self-similarity, which can be well described by fractals. And the discharge channels are an important factor affecting the distribution of discharge energy. The discharge process in kerosene and mixed powder dry medium have been simulated by using fractal theory. And the actual strengthening experiment was conducted in two different medium. The results prove that trajectory characteristics based on fractal theory are basically in agreement with the experiment result of EDM Surface Strengthening TC4 titanium alloy. The fractal theory can guide the EDM surface strengthening research of TC4 titanium alloy.

Abstract: A simulation model established by finite element methods using ANSYS software shows the distribution temperature field on titanium surface during misting strengthening process. The actual strengthening experiment was conducted. The results show that the simulation calculation results are consistent with those of experiments under the same strengthening experimental conditions. The simulation model is benefit to strengthening quality forecast, parameter regulation and optimization in the EDM strengthening process.

Abstract: One method of improving the strength of porous ceramics is to add Al₂O₃ in ceramic raw materials and then they must be sintered at high temperature for densification. However, the non-plastic property of Al₂O₃ leads to a decline in plasticity of clay body, thus severely interfering with forming process. Besides porous ceramics have fine cracks and pores distributed within porous ceramics, these fine cracks on the surface also result in weakening of the sintered body. In this study, we attempted to improve the strength while compensating for the weakness of porous ceramics by the surface infiltration of strengthening materials after the first sintering step at 900^°C. MgCl₂, Al (NO₃)₃, and KNO₃ were used as surface strengthening materials. The effect of Infiltration factors, solution concentrations (1-3 moles) and infiltration time (1-5 seconds) on the mechanical properties of the sintered body are investigated. When the strength was assessed after the second sintering step at 1250^°C, an 30% increase in strength was obtained with Al (NO₃)₃ infiltrated in a 3 mole solution for 5 seconds. An analysis of the crystal phase of the strengthened body revealed a higher intensity of the mullite phase arising from the infusion of surface strengthening materials. Consequently, the mullite phase led to a higher strength value.

Abstract: This article introduces the machining mechanism of rolling process and analyzes its influence on hardness, abrasion performance and fatigue strength of the work piece.

Abstract: In order to development the laser shock processing equipment, the technical features and process demand are analysis. The design requirements about laser shock processing equipment are discussed in detail by the methods of use case analysis and sequence diagram. Functional framework and technology architecture are put forward for the development of laser shock processing equipment. Finally, the equipment structure concept is given which is described for the future equipment design.