Materials Science Forum Vol. 1057

Abstract: Application of cutting fluids in machining can improve machinability but it may danger to the environment. An alternative to reduce this bad effect is by using minimum quantity lubrication (MQL). This study aims to determine the most optimal parameters in the AISI 4340 steel turning machining process to produce the best surface roughness with MQL conditions. The design method used is the Taguchi orthogonal array L9 ). The combined parameters are depth of cut, cutting speed, method of giving cutting fluid and feed rate. Based on the mean response value, it can be concluded that to get the most optimal results of surface roughness, the parameters are depth of cut 1.8 mm, cutting speed 120.89 m/min, method of giving cutting fluid by MQL method and feed rate 0.122 mm/rev. While the percentage contribution of the feed rate has the largest percentage, namely 57,02% and the cutting fluid method 41,33%.

Abstract: Ti-6Al-4V ELI is one of the titanium alloys commonly used as an implant material for its good biocompatibility. However, it has problems related to its corrosion behavior, especially when it is used for a long time. This study aimed to analyze the corrosion behavior of the implant material Ti-6Al-4V ELI in Hanks’ Balanced Salt Solution (HBSS) for a certain period, using the weight loss method in HBSS as the corrosive medium at 37°C. The immersion time was varied from two, four, until six weeks. Before immersion, the sample was thermomechanically treated with a combination of solution heat treatment at a temperature of 950°C and a holding time of 1 hour, water quenching, plastic deformation with deformation variations of 10%, 15%, and 20%, and, finally, aging heat treatment at a temperature of 550°C and holding time for 1.5 hours. The study results show that thermomechanical treatment and increased plastic deformation could reduce the corrosion rate and the metal ions released into the solution. These findings were evidenced by the corrosion rates of the pre-thermomechanical and the thermomechanical Ti-6Al-4V ELI with deformations of 10%, 15%, and 20% at the 6-week immersion of 6.57 x 10^-6 mmpy, 4.27 x 10^-6 mmpy, 3.89 x 10^-6 mmpy, and 2.76 x 10^-6 mmpy, respectively, and the metal ions released of 7.3 μg/L, 7 μg/L, 6.3 μg/L, and 6 μg/L, respectively. The corrosion rate of Ti-6Al-4V ELI under thermomechanical treatment, namely 2.76 x 10^-6 mmpy, was the lowest compared to other materials in HBSS, while the highest one was that of Ti-6Al-7Nb of 3.05 x10^-2 mmpy. In addition, the study results show that Ti-6Al-4V ELI under thermomechanical treatment is the best material compared to others for biomedical applications, based on corrosion resistance and metal ions released into HBSS.

Abstract: Development an ingot originated from the waste of aluminum product had many the advantages and could reduce the cost of aluminum metal production compared to primary process from ore. In this research used the waste of beverage aluminum cans One of the manufacturing methods conducted recycling aluminum waste is the casting process, Commonly, the problem with this casting process was that they are not homogeneous in the as-cast due to segregation. So that in this study a homogenization process on recycling aluminum castings would be carried out to obtain more homogeneous mechanical properties and microstructure. The variables that influence during the homogenization process was heating temperature and holding time. The heating temperature for this was in range from 450 C to 550 C, and the holding time was 2 to 4 hours. Further the effect of the parameter would observe. The observation included mechanical properties, such as tensile strength and hardness, and Microstructure of the ingot. The operation temperature and holding time influenced to grain size and hardness of Aluminum. In general, increasing homogenization temperature would reduce mechanical properties.

Abstract: The spread of disease by bacteria and viruses is very susceptible to outbreaks in public facilities through direct and indirect contact. Indirect contact occurs through intermediate such as housing equipment made of aluminum. One thing that people touch the most is door handles and frames. Aluminum frames are generally anodized to give a color effect because painted directly is difficult. Anodized products generally have a pore structure so that they can easily become an ideal place to grow and colonize bacteria and viruses. To overcome this, the coating process is carried out by electroplating. In this study, aluminum was treated with anodization and non-anodization. The concentration of sulfuric acid solution used was 0.5 M; 1M and 2M. The current used is 0.6A; 0.9A and 1.2M. Increasing the sulfuric acid concentration will increase the efficiency of the cathodic current and increase the mass of the deposit per unit area. Observation of the microstructure with an optical microscope shows the structure formed is dendritic in which the nucleus is continuous. The smooth and flat surface makes aluminum safe to be used and does not become a medium for bacteria or viruses to stick at aluminum surfaces.

Abstract: Stainless steels have wide application in the field of micro manufacturing industry. The size effect occur in thin metal foils because of low number of grain. Martensitic phase transformation (MPT) occur after plastic deformation subjected to stainless steel thin metal foils. Beside that, free surface roughening occur in thin metal foils after plastic deformation. The surface roughening mechanism in stainless steel thin metal foils after plastic deformation such as uniaxial tensile test not yet clarified well. MPT and grain misorientation (GMO) have huge effect to surface roughening behavior in stainless steel thin metal foils. The effect of GMO and MPT to surface roughening in SUS 316 and 304 thin metal foils were studied through uniaxial tensile stress state, repeated five times in 6% strain level for one time strain and 30% strain for the total of strain level. After that, an Scanning Electron Microcope-Electron Backscatter Diffraction (SEM-EBSD) analysis applied to 304 and 316 thin metal foils. The result showed that in stainless steel thin metal foil, surface roughening increase proportional both in fine gain (grain size 1,5 μm) and in coarse grain (grain size 9,0μm). The surface roughening in coarse grain, increased higher than in fine grain. The grain strength in SUS 304 is more inhomogeneous compared to SUS 316 that shown by SEM-EBSD results and as a result, increasing ratio of the surface roughness (Ra) is higher in fine grain and coarse grain of SUS 304 compared to SUS 316. The inhomogeneity of the grain strength in SUS 304 thin metal foil is higher than SUS 316 thin metal foil as shown by SEM-EBSD result. Furthermore, the increased surface roughness in stainless steel 304 is higher than stainless steel 316 thin metal foil both in fine grain and coarse grain. Key words : Surface roughening, Martensitic phase transformation (MPT), Grain Misorientation.

Abstract: Nitrogen doped as-cast Co-Cr-Mo alloy with markedly enhanced hardness and wear resistance was successfully produced by pack nitriding process. Nitriding proses used the in-pack process using urea fertilizer as a nitrogen source. It was carried out with variations in temperature of 400°C, 500°C, 600°C and followed by annealing. The wear resistance of the specimen is tested using pin-on-disk. The total sample will be soaked in the lactic acid solution for 3 days. The results obtained from the After nitriding process, the hardness of of speciment N400 obtained a hardness value of 261.54 HV speciment N500 of 309.68 HV, and speciment N600 of 429.14 HV, the results of the hardness value increased in each speciment. The wear resistance value obtained for each speciment N400, N500, N600 is 2,81 x 10^-6 mm³/Nm, 7,50 x 10^-7 mm³/Nm, 1,87 x 10^-7 mm³/Nm. The nitriding process forms a layer on the surface of the as-cast Co-Cr-Mo, it’s called Layer of Cr-N which is the result of heating/decomposing urea fertilizer into nitrogen gas which can coat the surface so that Cr-N bonds are formed in the layer. The thickness of the Cr-N layer on the N400 specimen is 0.28 mm, N500 is 0.35 mm, N600 is 0.38 mm. In addition, the surface results that have been tested for wear resistance form quite fine scratches but the formation of abrasions, such as abrasion, abrasion groove, delamination, and cohesive failure

Abstract: Ni-TiN/Si₃N₄ composite coatings on tungsten carbide were prepared by electrodeposition. The influences of electrodeposition temperature at 35 – 45 °C on coating microstructure and its impact to the mechanical and tribology properties were investigated to optimize the process parameter. A compact morphology of coatings gradually increased with increasing electrodeposition temperature that was addressed to the finer Ni crystallite size which resulted from co-deposition of TiN and Si₃N₄ particles. The finer crystallite size caused the increase of coating hardness with the highest (8.86 GPa) was achieved for the sample deposited at 45 °C. However, from the result of wear rate test, it was shown that the lowest wear rate (28.5 μm) was observed on the sample deposited at 40 °C.

Abstract: This study investigated the effect of degree of availability (d.o.a) of nitrogen and time on increasing the surface hardness of AISI H13 steel using pack nitriding. Urea (46 % N) and ZA (21% N) were selected as a nitrogen source. In this study, hardening was carried out at a temperature of 1030°C then held for 3 hours and continued to quenching with 19 bar nitrogen. Nitriding process used the in-pack process by which the specimens were buried in the urea and ZA powder charged into a nitriding box. Pack nitriding was performed in a vacuum furnace at 600°C for 2, 4 and 6 hours. The surface of nitride-steels was characterized using microhardness tester, SEM/EDS and XRD. After nitriding process, the hardness of AISI H13 steels was increased up to 1648 HV, with the highest hardness achieved by nitriding process of 6 hours and 0.4 d.o.a, in urea media. The nitrogen was dissolved to the steel and induced precipitation of Fe₃N, Fe₂N, and αFe. From the calculation based on Arrhenius equation, the activation energy (Q) of 0.4 and 0.3 d.o.a were 1.381 kCal/mol and 1.455 kCal/mol, respectively.

Abstract: Thermal Spray Coating is a material surface engineering process, where the coating material is heated until it melts then the melt is pushed with high-pressure air as individual particles or droplets to a surface. This study compares two thermal spray coating methods, twin-wire arc spray and wire flame spray to measure the level of hardness, coating strength and good quality of the coating and porosity. This study used medium carbon steel AISI 1045 as substrate and coating material with FeCrMnNiCSiSP alloy elements (AISI 420). Testing mechanical properties were undergone by hardness testing and pull-off test to determine the coating's adhesive strength. The microstructures were observed using a microscope to test the physical properties. After analyzing the research results, it can be concluded that the twin-wire arc spray coating process produces an adequate level of hardness and coating strength. Twin-wire arc spray can increase the percentage value of substrate surface hardness by 50,56 % and the average coating strength of 21,345 MPa. The microstructure observation results on the coating show that the coating results from twin-wire arc spray have good coating quality with the bonds between the elements contained in the FeCrMnNiCSiSP wire which are bonded to each other and form layered layers and minimal porosity in the coating.

Abstract: TiO₂ is a semiconductor that possesses superior chemical and physical properties, widely used in various fields. In this research, the synthesis of TiO₂ particles was carried out by the sonochemical method. Synthesis begins by mixing the precursor TiOSO₄ in H₂O with a ratio of the solvent volume (v/v) H₂O/TiOSO₄ 20-80. TiO₂ particles through sonochemically reduced for 15-75 minutes. Changes in particle diameter during the synthesis process are calculated by particle size analyzer. The results of the particle size analyzer showed that the increase in the solvent volume ratio causes the average diameter of TiO₂ particles to increase with a heterogeneous size distribution. Conversely, the increasing time on sonochemical processing causes a very significant decrease in the average particle diameter. The best parameter in the sonochemical method was the lowest solvent volume ratio, 20, and the sonochemical time process of 75 minutes generated a single anatase phase 338 nm with a spherical shape.