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"Pada proses pembentukan logam metode die casting, nitridisasi memegang peranan penting dalam peningkatan umur pakai dies. Inovasi proses perlakuan permukaan yang dilakukan sebelum nitridisasi bertujuan untuk meningkatkan efisiensi nitridisasi dan kedalaman lapisan nitrida pada baja H13 Modifikasi. Nitridisasi gas dilakukan dalam vacuum furnace, pada suhu 510°C selama 5 jam.Shot peening dilakukan dengan menggunakan bola baja dengan tekanan 461 kPa. Shot blasting dilakukan sebagai metode pembersihan permukaan material menggunakan partikel SiC. Karakterisasi permukaan sampel sebelum dan sesudah variasi proses difokuskan pada perubahan struktur mikro, distribusi kekerasan mikro, dan komposisi kimia lapisan nitridisasi. Dari proses nitridisasi yang didahului shot peening, didapatkan kekerasan maksimal 1196 HV dengan kedalaman efektif lapisan difusi 72 μm. Nilai ini lebih besar dari proses nitridisasi tanpa didahului perlakuan permukaan, yang menghasilkan kekerasan maksimal 1101,4 HV dengan kedalaman efektif lapisan difusi 54μm. Variasi proses nitridisasi dengan shot peening menghasilkan ketebalan white layer 4,1μm; lebih tebal dari proses nitridisasi tanpa shot peening 3,7μm. Sedangkan pada nitridisasi yang tidak didahului perlakuan permukaan tidak ditemukan adanya white layer.

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In the die casting practice, nitriding represents an important factor in enhancing the service life of dies. Surface treatment innovation prior to nitriding in this research aim to increased the nitriding efficiency and the depth of nitrided layer of H13 Modification steel. The gas nitriding process was performed at temperature 510°C for 5 hours in a vacuum furnace. Shot peening was performed prior to nitriding using a cast steel ball with 461 kPa nozzle pressure. Shot blasting with SiC particle was also performed as a surface cleaning method. Characterizations on the surface of steel were done before and after the variation of nitriding process with focused on the microstructure, microhardness profile, and the chemical composition of the nitrided layer formed. It was found that shot peening prior to nitriding significantly increased the nitriding kinetics, that results in 1196 HV maximum surface hardness with 72 μm effective case depth. This results were higher than the nitriding process without prior surface preparation, which have only 1101,4 HV maximum surface hardness with 54μm effective case depth. While the nitrided only process did not formed a white layer, the shot peened sample was found to have a white layer with 3,7μm thick."

"ABSTRAKIndustri pertambangan batubara di Indonesia semakin meningkat sejalan denganmeningkatnya kebutuhan manusia akan energi. Industri pertambanganmenghasilkan limbah oli bekas yang jumlahnya cukup besar yang memilikipotensi untuk dimanfaatkan sebagai subsitusi solar dalam pembuatan ANFOnamun banyak pelaku industri pertambangan yang belum memanfaatkan limbaholi bekasnya karena belum mengetahui proses, manfaat lingkungan, ekonomi dansosialnya. Penelitian ini bertujuan menganalisis proses pemanfaatan limbah olibekas dalam pembuatan ANFO serta menganalisis manfaat lingkungan, ekonomidan sosialnya. Penelitian ini menggunakan metode kuantitatif dan kualitatif yaitusurvei, wawancara mendalam dan kuesioner. Hasil penelitian menunjukkan bahwakegiatan pemanfaatan oli bekas sejak tahun 2012-2015 dapat mengurangi limbaholi bekas sebesar 3.585.233,33 liter, menghemat bahan bakar fosil sebesar3.887.602,41 liter dan memberikan keuntungan ekonomi bagi industri dalam halefisiensi biaya sebesar Rp. 38.876.024.096 dengan nilai NPV>0 dan B/C Ratio33,51 serta meningkatkan pengetahuan dan perilaku pekerja dalam halpengelolaan limbah. Kegiatan ini mendukung pembangunan berkelanjutan sektorpertambangan

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ABSTRACTCoal mining industry in Indonesia is increasing in line with the growing humanneed for energy. The mining industry generates large amount of used oil that haspotential to be used as a fuel mixture auxiliary blasting (ANFO) but there are stillmany perpetrators of the mining industry that have not been utilizing their usedoil because not knowing the process, environmental, economic and social benefitsof used oil utilization. This research aims to analyze process, environmental,economic and social benefits of used oil utilization. This research was carried outby applying quantitative and qualitative methods by undertaking survey, in-depthinterviews and questionnaires. The results present that used oil utilization from2012 until 2015 has environmental benefits that can reduce 3,585,233.33 liters ofused oil, saving on fossil fuels 3,887,602.41 liters and provides economic benefitsin terms of operational cost efficiency Rp. 38,876,024,096 with NPV>0 and B/Cratio 33.51 and improved the knowledge and behavior of workers in terms ofwaste management. Used oil utilization activities supporting sustainabledevelopment of the mining sector"

"Nozzle of RKX l00 rocket contributes 30 % to the total weight of the structure, so that allowing furtherresearch on weight reduction. An alternatiye for this is by substitution of massive graphite, which iscurrently used' as thermal protector in the nozzle, with thin layer of HVOF (High Velocity Oxy-Fuel)thermal spray layer. A series of study on the characteristics of various type of HVOF coating materialhave been conducted This paper presents the investigation on the HVOF Cr,C3-NiCr thermal spraycoating, particularly, the optimization of bonding strength by varying surface roughness of substrates.Characterization includes bonding strength test, microhardness measurement and microstructuralanalysis by both optical and scanning electron microscopes (SEM). The results showed that grit blastingpressure increases the surface roughness from 4.54 ,urn to 5.72 _um at the pressure of 6 bar. Averagemicrohardness of the coating is 631 VHN_;m.Coating applied to the Surface with roughness of 5.42 ,annpossessed the highest bonding strength of 4 4 MPa. Microstructural observation by using opticalmicroscope and scanning electron microscope (SEM) confirmed dense lamellae structure with variablecomposition. High coating adherence was found to be due to mechanical interlocking."