The Hardness and Microstructure of The Modified 13Cr Steam Turbine Blade Steel in Tempered Conditions

Abstract

Abstract-Martensitic stainless steels were usually used for turbine blade. Their properties can be improved in various ways, such as by heat treatment. This paper reports the influences of tempering temperature on hardness and microstructure of the modified 13Cr martensitic stainless steels. Samples were austenitized at 1050C and tempered at 300, 400, 500, 550, 600, 650, and 700ºC. Hardness measurement was conducted by Rockwell C indentation and metallographic observation was conducted by scanning electron microscope (SEM). The results show that increasing tempering temperature until 500C can improve hardness. The microstructure formed consists of tempered martensite containing carbides M 23 C 6 . The presence of carbides can also increasing hardness. Increasing tempering temperaturefrom 500C to 650C can decrease Cr content of carbide. Keyword-Steam turbine blade, Martensitic stainless steel, Carbide I. INTRODUCTION Martensitic stainless steels were commonly used for manufacturing component due to their high mechanical properties and moderate corrosion resistance, operating at either high or low temperature. Due to their properties could be improved by heat treatment, these steels are suitable for various application such as turbine blade [1]- [3]. However, the failure of the blade frequently found in service due to mechanical and environmental interaction which operated in turbine system. Furthermore, almost 50% the failures of turbine blade are related to fatigue, pitting corrosion, stress corrosion cracking, and corrosion fatigue [4].The mechanical properties and corrosion resistance of martensitic stainless steels depend on chemical composition and heat treatment. Heat treatment process of these steels commonly involved solid-solution treatment (ausenitizing) to form an austenite structure, and dissolving carbides, followed by cooling or quenching to transform austenite into martensite structure, and then followed by tempering to obtain carbide precipitation [5]. The amount of carbide can affect mechanical properties and corrosion resistance in this material. The presence of retained austenite may affect wear resistance, fatigue properties, and ductility [6].The addition of small increase Molybdenum (Mo) and Nickel (Ni) in stainless steel can contribute to increase corrosion resistance. Mo is particularly effective to increase corrosion resistance, but only in presence of Chromium (Cr). Various explanations have been reported for the effect of Mo to increase corrosion resistance [7,8]. The modified 13Cr martensitic stainless steel containing Ni and Mo are being developed in our laboratory [9]. This study reports on the hardness and microstructure of the modified 13Cr3Ni3Mo martensitic stainless steel with respect to tempering temperature.II. EXPERIMENTAL PROCEDURE The modified 13Cr martensitic stainless steel ingot was prepared in electric induction furnace. The ingots of 5x5x10 cm in dimension were hot forged at around 900-1100C until the dimension of the ingots decreased to about 12x6x2 cm. The square...

Strukturmikro, Kekerasan, dan Ketahanan Korosi Baja Tahan Karat Martensitik 13Cr3Mo3Ni Hasil Quench-Temper dengan Variasi Temperatur dan Waktu Austenisasi [Microstructure, Hardness, and Corrosion Resistant of Martensitic Stainless Steel 13Cr3Mo3Ni after Quench-Temper with Various Austenization Temperature and Time]

“…Mo akan sangat efektif meningkatkan ketahanan korosi, hanya jika ada kehadiran Cr di dalam baja tersebut [7][8] . Pada penelitian sebelumnya telah dijelaskan tentang penambahan unsur Mo dan Ni ke dalam baja tahan karat martensitik dapat memperbaiki sifat mekanik dan meningkatkan ketahanan korosi [9][10][11][12] . Namun, sifat mekanik dan ketahanan korosi baja tahan karat tersebut masih dapat diperbaiki dengan perlakuan panas.…”

Improving Fatigue Corrosion Resistance of Turbine Blades Using Laser Processing

“…Concerning this metal, the quantity of carbide may impact its mechanical qualities and corrosion resistance. In addition, Austenite retention may affect wear resistance, fatigue life, and ductility [5]. Surface modification technology has grown in relevance as laser applications in automobiles, airplanes, ships, and other heavy sectors have expanded rapidly.…”