The effect of heat treatments on the corrosion fatigue properties of 13 Pct Chromium Stainless Steel in 3 Pct NaCI Aqueo
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INTRODUCTION
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M A R T E N S I T I C stainless steels are being widely used as the blading material of marine or compressor driving turbines. In such apparatus condensation of the small amount of various impurities contained in steam is presumed to occur at some regions where wetting and drying are repeated, and the material there is thus exposed to the aggressive environment. Consequently, an occurrence of the corrosion fatigue is presumed. In fact, failure analyses of the actually used moving blades indicate the suspicion of corrosion fatigue in many cases. ~Thus, corrosion fatigue properties are essential in designing the turbines, and the effects of various factors such as temperature, frequency, mean stress, and so on on the corrosion fatigue of the martenstitic stainless steels are reported, z,3 Extensive evaluation of the fatigue crack propagation (FCP) rate properties of type 403 stainless steel in various marine turbine environments are also reported. 4 Ebara et al made a systematic study on the corrosion fatigue of 13 pct chromium steel at various aqueous or steam environments, s-8 Critical action of NaC1 and NaOH in the aqueous solution was clarified. However, these above mentioned results were mostly on the standard heat treated materials (hardened and then annealed at 650 to 760 ~ and relatively little is known about the effect of austenitizing or tempering temperature on the corrosion fatigue of this type of martensitic stainless steel. In this paper the effect of heat treatments on the fatigue strength and FCP behavior of 13 pct chromium steel in air and 3 pct NaC1 aqueous solution is reported for the aim of getting the basic data to clarify the corrosion fatigue properties of this material. HITOSHI ISHII is Associate Professor, Department of Mechanical Engineering, Shizuoka University, Johoku, Hamamatsu 432, Japan, YUJI SAKAKIBARA is Researcher, Toyota Central Research and Development Laboratories, Inc., Nagakute, Aichi-gun 480-11, Japan, and RYUICHIRO EBARA is Senior Research Engineer, Hiroshima Technical Institute, Mitsubishi Heavy Industries, Ltd., Hiroshima 733, Japan. Manuscript submitted August 31, 1981. METALLURGICAL TRANSACTIONS A
EXPERIMENTAL P R O C E D U R E
The chemical analyses of the electro-slag melted 13 pct chromium stainless steel (SUS 410J1) used in this study are listed in Table I. This material was supplied as an annealed 70 mm x 120 mm • 2,000 mm long forged bar stock. The stock was then cut into small pieces and the various heat treatments listed in Table II were applied. Then, two types of the fatigue specimens shown in Figure 1 were machined. Type (a) test pieces were made to obtain S-N curve data using a rotating cantilever machine (Wh61er type) at a frequency of approximately 60 Hz. Type (b) test pieces which contained a central slit, the details of which are also shown in the same figure, were used for FCP measurements. Type A-1 and A-2 slits were for the test in 3 pet NaC1 aqueous solution and in air, respectively. The test pieces which were applied various hea
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