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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...

This research studied the effect of the addition of sulfur on the reduction process of limonite nickel laterite ore with Ni content of 1.11wt% and Fe 48.7wt%. The stages of the research included the characterization of ore materials, preparation, mixing, pelleting, reduction, and magnetic separation. The reduction stage was carried out with several experimental variables, which were the time and temperature of the reduction, as well as the addition of reducing agents and sulfur additives. Products from the reduction process were separated magnetically, and the concentrate was then analyzed using XRD and AAS. The results showed that the addition of sulfur additives to a certain amount could cause the formation of FeS and Fe-silicate, which could increase the content and percentage of nickel recovery by suppressing the metallization of iron. The optimum conditions were obtained in the reduction process with a temperature of 1100°C for 60 minutes, with the addition of graphite reductant and sulfur additives each of 7% of the sample weight. Ni contents in the reduction product concentrate obtained were 1.98% with 96% gain, while Fe could be reduced to 29.2% with an extraction percentage of 76.1%.

The aim of iron ore direct reduction process is to convert iron oxide into metallic iron. The conversion of iron oxide into metallic iron occurs through saveral stages of intermediate phase. This intermediate phase included of hematite, magnetite and wustite. Temperatures is one of the important variables to ensure the trasformation of the phase completly. Generally in the direct reduction process, iron oxide process should be agglomerated into 1,5 cm – 2 cm in diameter spherical or cylindrical pellet. Agglomerates form, caused unevan temperatur distibutions within pellet inside. The objectives of this work is to observed energy and the rate of heat flux during reduction process so that intermadiate phase can be trasformed perfectly into metallic iron. To analize temperatur pellet inside, Ansys software was utilized to simulated iron ore direct reduction process. This simulation using agglomerate spherical form. Temperatures simulation take place at 900 into 1100 Celcius for 30 and 69 minute. This simulation also simulated carbon monoxide (CO) as reduction gas at 1 atm

ABSTRAKPemanfaatan pengolahan scrap kaleng minuman aluminium dapat digunakan sebagai bahan sekunder pada proses manufaktur produk aluminium. Ingot hasil daur ulang scrap kaleng minuman aluminium diharapkan dapat mengurangi biaya produksi, mengurangi polusi yang ditimbulkan serta dapat memenuhi kebutuhan aluminium di Indonesia. Penggunaan flux merupakan salah satu metode yang digunakan untuk mengurangi unsur pengotor pada aluminium paduan disamping itu flux dapat melindungi logam cair berikatan dengan oksigen. Di dalam penelitian ini digunakan scrap kaleng minuman yang terdiri dari scrap kaleng minuman berkarbonasi, isotonik dan penyegar. Pembuatan ingot dari bahan baku scrap kaleng minuman aluminium menggunakan variasi waktu tahan proses fluxing selama 60, 120, 180 dan 240 menit dan variasi penambahan massa flux sebanyak 5, 10 dan 15% dari total massa scrap. Kemudian dilakukan pengujian terhadap ingot yang dihasilkan untuk mengetahui persen penurunan kadar Mg dan perolehan Al menggunakan analisa teknik XRF, pengujian metalografi terhadap ingot untuk melihat strukturmikro hasil daur ulang. Hasil penelitian menunjukkan bahwa persen reduksi Mg tertinggi adalah 77,83% pada sampel penambahan 15% flux dengan waktu tahan selama 120 menit, perolehan Al tertinggi didapatkan sebesar 97,49% pada sampel penambahan 15% flux dengan waktu tahan 240 menit. Untuk nilai persen yield, recovery dan recycling efficiency, nilai tertinggi pada penambahan 10% flux dengan waktu tahan 180 menit dengan masingmasing nilai sebesar 98,82% untuk yield, 71,84% untuk recovery dan 70,53% untuk recycling efficiency. ABSTRACTThe utilization of aluminum beverage scrap processing can be used as a secondary material in the manufacturing process of aluminum products. Ingot recycled scrap aluminum beverage cans are expected to reduce production costs, reduce pollution generated and can meet the needs of aluminum in Indonesia. The use of flux is one of the methods used to reduce the impurity element on aluminum alloy beside that flux can protect molten metal binds to oxygen. In this study used scrap beverage cans consisting of carbonated beverage scrap cans, isotonic and refreshing. Ingot ingredients from scrap aluminum beverage cans using variation of fluxing resistance time for 60, 120, 180 and 240 minutes and variations of flux mass increase of 5, 10 and 15% of total scrap mass. Then tested the resulting ingot to know the percent decrease of Mg and Al recovery using XRF technique, metallographic test to ingot to see recycled microstructure. The results showed that the highest reduction percentage of Mg was 77.83% in a sample of 15% flux addition with a duration of 120 minutes, the highest Al gain was 97.49% in the sample of 15% flux addition with 240 min. For percent yield, recovery and recycling efficiency, the highest value is 10% flux with 180 minutes of duration with 98.82% for yield, 71.84% for recovery and 70.53% for recycling efficiency.