Austenityczna stal nierdzewna jest uważana za materiał o doskonałej odporności na korozję i akceptowalnych właściwościach mechanicznych, zalecany do różnych zastosowań konstrukcyjnych, przemysłowych i biomedycznych. W agresywnych środowiskach chlorkowych jest ona podatna na miejscową korozję wżerową. Oceniono odporność na korozję stali nierdzewnej typu AISI 316Ti o powierzchni pasywowanej kwasem azotowym w kwasowym 1 M roztworze jonów chlorkowych w temp. 22-80°C. Ocenę tę oparto na wynikach ekspozycyjnych testów zanurzeniowych i wynikach elektrochemicznej spektroskopii impedancyjnej (EIS).
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Com. Ti-stabilized Cr-Ni-Mo austenitic stainless steel was passivated with HNO₃ soln. and then studied for pitting corrosion in 5% FeCl₃ soln. (pH 1.2) by 24-hours std. immersion test and in 0.9 M NaCl + 0.1 M HCl soln. (pH 1.1) by electrochem. impedance spectroscopy (EIS test) at 22- 80°C. The pits were significantly bigger at 22°C than those at 50°C but the distribution of pitting was markedly lower. The polarization resistance decreased with increasing the temp. The quality of the surface passive film was several times lower at 80°C than at the lower temp.
The Ni-base superalloys are used in the aircraft industry for the production of aero engine most stressed parts, turbine blades or turbine discs. Quality of aero jet engine components has a significant influence on the overall lifetime of a jet engine as itself as well as the whole airplane. From this reason a dendrite arm spacing, grain size, morphology, number and value of γ' - phase are very important structural characteristics for blade or discs lifetime prediction. The methods of quantitative metallography are very often used for evaluation of structural characteristics mentioned above. The high-temperature effect on structural characteristics and application of quantitative methods evaluation are presented in this paper. The two different groups of Ni-base alloys have been used as experimental material: cast alloys ZhS6K and IN713LC, which are used for small turbine blades production and wrought alloys EI 698VD and EI 929, which are used for turbine disc production. Selected alloys have been evaluated in the starting stage and after applied heattreatment at 850°C for 24 hrs. This applied heat-treatment causes structural changes in all alloys groups. In cast alloy dendritic structure is degraded and gamma prime average size has grown what has a negative influence on turbine blade creep rupture life. Wrought alloys show partially grain boundary melting and grain size changed due to recrystallization what causes mechanical properties decreasing - ultimate tensile strength mainly.
This article deals with determining of fatigue lifetime of aluminum alloy 6063-T66 during by multiaxial cyclic loading. The experiments deal with the testing of specimens for identification of the strain-life behavior of material, the modeling of combined loading and determining the number of cycles to fracture in the region of low-cycle fatigue. Fatigue tests under constant amplitude loading were performed in a standard electromechanical machine with a suitable gripping system. Based on the experimental results the fatigue design curves are compared to the fatigue data from the base material and the welded material and also multiaxial fatigue models, which are able to predict fatigue life at different loads.
AISI 304 austenitic stainless steel is recommended and used for various applications in industry, architecture and medicine. Presence of halides in environment evokes a possibility of the local corrosion which limits seriously exploitation of this material in aggressive conditions. The presented paper is focused on the pitting corrosion resistance (“as received” steel surface) in 1M chloride solution (pH=1.2) at a common (20 °C) and an elevated (50 °C) ambient temperatures. 24-hours exposure immersion test (ASTM G48) and cyclic potentiodynamic test (ASTM G61) are used as the independent test methods. The exposure immersion test is carried out with cross-rolled and longitudinally rolled specimens and the effect of direction of rolling on the resistance to pitting is studied.
Carbon fiber reinforced composite materials offer greater rigidity and strength than any other composites, but are much more expensive than e.g. glass fiber reinforced composite materials. Continuous fibers in polyester give the best properties. The fibers carry mechanical loads, the matrix transfers the loads to the fibers, is ductile and tough, protect the fibers from handling and environmental damage. The working temperature and the processing conditions of the composite depend on the matrix material. Polyesters are the most commonly used matrices because they offer good properties at relatively low cost. The strength of the composite increases along with the fiber-matrix ratio and the fiber orientation parallel to the load direction. The longer the fibers, the more effective the load transfer is. Increasing the thickness of the laminate leads to a reduction in the strength of the composite and the modulus of strength, since the likelihood of the presence of defects increases. The aim of this research is to analyze the change in the mechanical properties of the polymer composite. The polymer composite consists of carbon fibers and epoxy resin. The change in compressive strength in the longitudinal and transverse directions of the fiber orientation was evaluated. At the same time, the influence of the wet environment on the change of mechanical properties of the composite was evaluated.
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