Modifikasi Sifat Mekanik Dan Ketahanan Korosi Paduan Fe-1,52Al-1,44C Dengan Proses Tempiring

Aluminum is third of biggest element in the world and cheaper relatively. The Fe-Cr-C alloy is promised alloy to replace the Fe-Cr-C alloy. The purpose of the research is to investigate influence of temperature to microstructure, tensile strength, hardness, and corrosion resistance of Fe-Al-C in the 3.5% NaCl solution. Raw material for casting is low Mn steel, FeMn HC, pure aluminum, slag remover. The melting used low frequency induction furnace which has 50 kg capacity. Hardening at 900oC, and then quenching in the water, the last temper along 1 hour with various temperature; 250oC, 300oC, 350oC, 400oC, 450oC and cooling in the air. Chemical composition, microstructure, tensile strength, hardness, and corrosion resistance of Fe-Al-C in the 3.5% NaCl solution were investigated. The result of the chemical composition investigation showed that Fe-Al-C alloy contained 1.52% Al, and 1.44% C. The microstructure of Fe-1.52 Al-1,44C alloy is ferrite and pearlite. The tensile strength of Fe-1.52 Al-1,44C alloy is 33.77 kg/mm2. The tensile strength raised after hardening process became 74.44 kg/mm2 and turn off again after tempering process. The Vickers hardness investigation showed that the Fe-1.52 Al-1,44C alloy has 232.4 VHN and raised after hardening became 298.7 VHN. Highest corrosion rate is 0,927 mm/year after hardening and lowest is 0.196 mm/year after tempering at 300oC (good category corrosion resistance)

Corrosion Resistance of AISI 316L after Short Holding Time of High Temperature Gas Nitriding (HTGN)

Stainless steel AISI 316L is widely used as biomaterial due to its high corrosion resistance. However this property decreases in highly stressed and oxygen depleted environments. Several methods have been developing to increase the corrosion resistance such as low and high temperature gas nitriding. High temperature gas nitriding (HTGN) produces more depth effect than low temperature gas nitriding. Unfortunately HTGN for long holding time results on grain coarsening which reduce its tensile strength. The objective of this research is to determine the effect of HTGN at short holding time on the corrosion resistance, hardness and grain coarsening of AISI 316L. Specimens were made from as rolled 1 mm thickness AISI 316L plate. Before HTGN process, the specimens were rinsed using ultrasonic cleaner in acetone medium. HTGN process was conducted at temperature 1050oC, 1100oC and 1200oC for short period holding time i.e. 15 and 30 minutes. Micro hardness, microstructure and corrosion tests were conducted in the simulated body fluid (SBF) to evaluate the process. The results show that hardness and corrosion resistance were increased significantly after HTGN process. Moreover, hardness for holding time of 30 minutes was higher than 15 minutes, however the corrosion resistance were decreased. In addition HTGN process also results on grain coarsening at 30 minutes holding time, however for holding time 15 minutes and temperature 1050oC and 1100oC did not give significant grain coarsening. Therefore, the HTGN process parameters must be optimized for compromise between hardness and corrosion resistance. Keywords: high temperature gas nitriding, corrosion resistance, grain coarsening, AISI 316

Efek Dendrite Arm Spacing terhadap Sifat Mekanis Paduan Perunggu Cu-20%Sn

The purpose of this work is to investigate the effect of dendrite arm spacing on mechanical properties bronze20%Sn alloys The commercial pure copper and tin were melted in crucible furnace at temperature 1000oC. The molten metalwas casted in permanent moulds which have variation temperature, i.e. 35oC, 200oC, 400oC. The history of coolingtemperature on castings was recorded using a computer aided data acquisition Lab view 8.2 system.The microstructure and mechanical properties of this alloy have been investigated. The results of this researchindicate that decreasing the mould temperature affected on increasing solidification rate that caused to reduce thesolidification time. On the other hand, the difference of solidification rate have effected on microstructure forms. Thedendrite arm spacing (DAS) decreases with increasing solidification rate. DAS affected on mechanical properties i.e.ultimate tensile strength and hardness as cast. The mechanical properties increase with decreasing DAS