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...

IntisariBaja tahan karat 13Cr3Mo3Ni merupakan modifikasi dari baja tahan karat martensitik 410 untuk digunakan sebagai material sudu pada turbin uap. Tulisan ini memaparkan pengaruh suhu dan waktu tempering terhadap kekerasan, struktur mikro dan laju korosi baja tahan karat martensitik 13Cr3Mo3Ni. Pengujian yang dilakukan adalah pengamatan struktur mikro menggunakan mikroskop optik dan SEM-EDS, uji kekerasan dengan Rockwell C dan uji korosi di dalam larutan 3,5% NaCl dengan alat Gamry G750. Secara umum kekerasan baja menurun dengan naiknya suhu tempering, kecuali pada suhu 500-650 °C terjadi peningkatan kekerasan akibat adanya secondary hardening dan karbida logam berukuran sub-mikron teramati sebagai penyebabnya. Peningkatan waktu tempering menjadi 6 jam mengakibatkan penurunan kekerasan dan penghilangan efek secondary hardening. Perbedaan suhu tempering juga menghasilkan perbedaan potensial, arus serta laju korosi baja 13Cr3Mo3Ni.