No abstract available

[en] It was attempted to describe the liquid erosion of metals by means of an analytical model based on physical and technological facts. Thus, quantitative prognoses are possible. The essential damage mechanism is considered to be fatigue combined with plastic shear effects immediately on the surface. The material attributes have been included by a statistical model. So they are largely characterized by parameters of distribution functions. A first comparison of theory and experiment has been realized using accepted experimental results. An application of this model might be found in supporting and substituting expensive experiments respectively by model results. It might also be possible to get a priori estimations of erosion resistance. (author)

[en] It was attempted to describe the liquid erosion of metals by means of an analytical model based on physical and technological facts. Thus, quantitative prognoses are possible. The essential damage mechanism is considered to fatigue combined with plastic shear effects immediately on the surface. The material attributes have been included by a statistical model. So they are largely characterized by parameters of distribution functions. A first comparison of theory and experiment has been realized using accepted experimental results. An application of this model might be found in supporting and substituting expensive experiments respectively by model results. It might also be possible to get a priori estimations of erosion resistance. (author)

[en] This paper presents the long-term monitoring results from the water droplet erosion (or moisture erosion) and the analysis of the service life of the last stage rotor blades, particularly the flame-hardened and Stellite-brazed blades, of LP (Low Pressure) section in Gori, Wolsung, Youngkwang, and Uljin nuclear power plants. The flow of wet steam caused the considerable erosion damage on the leading edge of the last stage rotor blades. Characterization of the erosion process with the operation time has shown that there were three characteristic modes including the first region without showing evident material loss, the second region with a drastic material loss with maximum erosion rate, and the third region with relatively slow erosion rate. Such erosion behavior indicated that the erosive damage on the material was developed by the fatigue fracture induced by repeated impact loads. Based on the simplified model and calculation, the service life of the last stage rotor blade has been estimated at about 223000 hrs for the flame-hardened blade and 185000 hrs for the Stellite-brazed blade

[en] The aim of this work is to show the implication of the experimental parameters (welding temperature, temperature holding time, lining pressure, surface states, atmosphere) on the bonds quality. On the other hand, the feasibility of an homogeneous bond has been shown on two materials prepared by the Haynes firm: the HR-120 (iron-nickel-chromium alloy which has good properties at high temperature: 1100 C) and the HR-230 (other iron-nickel-chromium alloy which has a very good resistance at high temperature: until 1150 C and at oxidation too). The study of welding specimens by metallographic analysis allows to conclude to the establishment of healthy bonds, particularly if the experimental parameters are scrupulously respected. (O.M.)

[en] The first domestically-made steam pump found cracks in the Stellite surfacing layer of the balance disk during the overhaul disassembly. In this paper, through the microscopic morphology, energy spectrum measurement and crack profile observation of cracks, the inducement of cracks was derived. After researching the calculation process of the axial force of the rotor of the steam pump and combing the shortcomings of Stellite surfacing and machining processes, the root causes of the cracks were summarized. After taking corresponding measures, the balance disc manufactured using the new process has undergone factory test verification, which significantly improves the crack resistance and expansion ability of Stellite alloy surfacing layer, also improves the equipment reliability. Above all, this provides a good engineering reference for optimizes and improves domestic steam-driven pumps for HPR1000. (author)

No abstract available

No abstract available

[en] Co-based alloys are used over a wide range of application because of their excellent corrosion and wear properties. Especially the Stellites (Co-Cr-W) are well known and quite well researched. The CoCrTaAlCSiY is a new material on the field of thermal spray coatings and due to its composition was chosen for studding of tribological behavior. In this paper the HVOF sprayed and post heat treated coatings of CoCrTaAlCSiY are presented. Specimens were treated by a laser with two different laser parameters in order to reach different thickness of laser treated layers. Erosion test and linearly oscillating ball-on-flat test were applied to evaluate the wear behavior of CoCrTaAlCSiY coating. Microstructure of as-sprayed and heat treated coatings were also studied. The evaluation revealed a positive effect on wear coefficient for both laser treated coatings. A significant improvement of volume loss during erosion test was also observed for both laser treated coatings. (paper)

[en] The microstructural and mechanical properties of a MnFeCoNiCu braze filler are analyzed and compared to a conventional nickel-based braze filler alloy on Haynes 214 as the base material. Tensile tests reveal that the samples brazed with the MnFeCoNiCu compositionally complex alloy (CCA) exhibit superior ductility increased by a factor of 1.6 compared to those brazed with the nickel-based filler. The ultimate tensile strength remains comparable (factor 1.03). Contact angles recorded during the brazing process indicate comparable wetting properties between the two fillers. Based on experimental investigations and Thermo-Calc predictions, improved brazing parameters are proposed for the CCA filler on Haynes 214. These recommendations include lower brazing temperatures, shortened holding times, and faster cooling rates. (© 2024 The Author(s). Advanced Engineering Materials published by Wiley‐VCH GmbH)