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Die soldering occurs when molten aluminum sticks to the surface of a die material and remains there after the ejection of the part. This resulted in low productivity and economic value in the foundry industry. Nitriding surface treatment is considered as an effective way in enhancing the service life of AISI H13 steel dies and to prevent soldering effect. The focus of this paper is to investigate the influence of three different surface conditions in terms of roughness, gas nitriding and pretreatment prior to gas nitriding on the soldering effect. Three kind of samples made of AISI H13 steel were pretreated (quenched and tempered) and followed by : shot peened, gas nitrided and shot peening followed by gas nitriding, were immersed in liquid melted ADC 12 Aluminium alloy at 30 seconds, 30 minutes, 2 hours and 5 hours, at a constant temperature of 680oC in a holding furnace. Characterizations on the surface of the steel were focused on the optical microstructure, microhardness profile, FE SEM observation and enegy dispersive spectrometry mapping. It was found that shot peening prior to nitriding gives a higher surface hardness and depth of nitride layer of H13 tool steel, 1140 HV (>70 HRC) and 120.5 μm, than the nitriding only process, 1033 HV (68 HRC) and 105 μm. The higher the hardness and depth of nitride layer expected would reduce the die soldering effect at the surface of the H13 tool steel dies. It was also found that the only shot peening treatment resulted in a tendency of soldering accompanied by the formation of intermetallic layers ; while soldering is not found on the nitrided and shot peened-nitrided samples.

AbstrakPembuatan komposit matriks logam Al-SiC dapat dilakukan dengan metode infiltrasi tanpa tekanan (PRIMEX). Penelitian ini dilakukan dengan menggunakan ingot alumunium AC2B sebagai matrik dan 50%Vf serbuk SiC sebagai penguat yang dicampur dengan 10%wt Mg sebagai wetting agent. Waktu tahan dan suhu pemanasan pada penelitian ini divariasikan untuk melihat pengaruh waktu tahan dan suhu pemanasan terhadap sifat mekanik dari komposit Al-SiC. Waktu tahan yang digunakan adalah 2, 5, 8, 10, dan 12 jam sedangkan suhu pemanasan yang digunakan 750, 800, 900, 1000, dan 1100°C. Komposit yang diperoleh dianalisa baik sifat mekanis seperti densitas, porosital, kekerasan, laju aus dan metalography. Lamanya waktu tahan dan meningkatnya suhu pemanasan menghasilkan sifat mekanis yang lebih baik dari komposit logam Al/SiC tersebut, dan ditemukan bahwa kondisi optimum untuk mendapatkan sifat mekanis yang baik adalah pada kondisi waktu tahan 10 jam dan suhu pemanasan 1000°C. Abstract Effect of Firing Temperature and Holding Time on Characterization of Al/SiC Metal Matrix CompositesProduced by Pressureless Infiltration. The production of Al-SiC metal matrix composite can be carried out by pressureless metal infiltration processs (PRIMEX). The experiment was conducted using aluminium AC2B ingot as a matrix and 50%Vf SiC powder as a reinforcement which is mixed with 10% Mg powder for wetting agent. The variables of this experiment are holding time and firing temperature to investigate the effect of these conditions on mechanical properties of Al-SiC metal matrix composites. Holding time was conducted for 2,5,8,10,12 hours and firing temperatures was 750, 800, 900, 1000, 1100°C respectively.. The composites produced are analysed both mechanical properties and metalography such as densities, porosities, hardness, as well as wear rate. The results showed that the longer holding time and increasing firing temperature will increase mechanical properties of Al-SiC metal matrix composites, and it is found that the optimum mechanical properties at 1000°C for 10 hour.

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