Wahyono Suprapto

Bee Wax Propolis Extract as Eco-Friendly Corrosion Inhibitors for 304SS in Sulfuric Acid

The inhibition properties of bee wax propolis (BWP) extract on the 304SS in 0.5 M sulfuric acid were conducted using potentiodynamic polarization, EIS, and XRD. Quercetin (2-(3.4-dihydroxy phenyl)-3.5.7-trihydroxy-4H-chromen-4-one) was identified as the main compound in the BWP extract based on FTIR and HPLC analysis. The results showed that the inhibitor could retard the corrosion rate of 304SS in 0.5 M sulfuric acid which reached 97.29% and 91.42% at 2000 ppm based on potentiodynamic polarization and EIS measurement, respectively. The inhibition efficiency decreased with increasing temperature. The inhibition mechanism of BWP extract on the 304SS was physisorption and obeyed Temkin adsorption isotherm equation. The thin protective layer on the 304SS surface was confirmed by XRD.

Torsion strength of continuous drive friction weld joint of round bar aluminum A6061 affected by single cone geometry of friction area

This paper describes the effect of single cone geometry of friction area on torsion strength of continuous drive friction weld (CDFW) joint of round bar aluminum alloys A6061. Single cone geometry on friction area was determined with ratio of upper diameter (D1) and lower diameter (D2), D1/D2 of cone. Ratios of D1/D2 used were 0.02, 0.25, 0.65, 0.8 and 1. Friction time was 120 seconds. Torsion strength test, macro and microstructure, micro-hardness test were conducted. The results show that D1/D2 of 0.25 gives maximum torsion strength of CDFW joint. It is thought that it occurs due to the wider area of Zpl zone, smaller grain size and more Mg2Si precipitate in the Zpl and Zpd zone and nil or minimum porosity in the CDFW joint.

Effect of Low Temperature Sintering on the Porosity and Microstructure of Porous Zeolite Ceramic

Manufacturing a porous ceramic specimen from natural zeolite materials mined in Malang, Indonesia was conducted by using a low temperature sintering. In this study, a porous ceramic property with rectangular shaped and prism shaped fillets at each end were sintered at 800-900°C and finally were investigated. Density and porosity measurements were performed using Archimedes method. The microstructure photos were used to measure the neck diameter and the contact angle between the two grains particles and two-dimensional porosity. The result of the zeolite ceramic measurement shows that the higher the sintering temperature the higher the density value and the smaller the open porosity. While from the microstructure photo it is shown that the neck diameter was larger the contact angle was wider. This phenomenon was happened because of the flux diffusion on the grain boundaries. This diffusion flow condition would influence the specimen surface, volume and grain boundary so that the porous ceramic density increases.

THE POSITION OF THE JOINTS WITH ANGLE OF 90° AT FRICTION STIR WELDING (FSW)

This research was use aluminum 6061 with 150 mm length, 50 mm wide, and 10 mm thick. The probe was made from EMS 45 simple design. Three variations used of feedrate speed is 10 mm/min, 15 mm/min, and 30 mm/min. Spindle rotation constantly set 2000 rpm, the heat generated was recorded. Corner-Butt (C-B)joint determined, the lowest heat generated from 2200C3200C and the tensile test was60 MPa. The highest tensile testwas 163 MPa, achieved by Corner-butt 45 (CB 45) joint on 10 mm/min feedrate speed. It was verified by the heat temperature from 3000C-4200C and clarified by its micro and macrostructure.

White Layer Control on AISI 316L Using Temperature and Gas Nitriding Diffusion Stage Process

The aim of the study was to compare the hardness properties resulting after the nitriding fluidized bed thermochemical treatments in different media and the diffuse temperature process, to evaluate the efficiency of the white layer formation on stainless steel substrats. The White layer is a layer with a high nitrogen atom concentration between the surface and the layer underneath. This concentration causes the layer to be hard and brittle. The use of diffusion stage after the boost stage (550 0C) in a fluidized bed reactor aims at reducing the formation of the white layer. The results show that a reduction in white layer is followed by the increase of brittleness in the form of crack formation in the layer underneath. The imbalance reaction due to the exothermic reaction is the primary reason. An increase in the atmosphere temperature without nitrogen gas during the diffusion stage increases the supersaturated reaction. The optimal process is fixed diffusion at boost temperature of 550 0C in the gas diffusion media without nitrogen. The use of atmosphere without nitrogen gas during diffusion increases the depth of diffusion of the nitrogen atom and reduces the white layer, thereby reducing brittleness. In addition, micro-cracks have been formed under white layers at the higher diffusion temperature of 650 0C. Copyright

Effect of N and C on surface formation of jagged - nodular and nitride-carbide structure on hard chrome steel during thermochemical treatment

The morphology of surface structure was changed from jagged to nodular structure. Martensite structure is formed from hard chrome plating after the oxidised diffusion of nitriding process. The investigation was conducted using SEM, EDAX, AFM and spectroscopy. This phenomenon belongs to an unusual structure. The morphology of crack density that disappears depends on the diffusion media of nitriding process. Such phenomena also happened under hard chrome plating forming carbide and bainite structure. With the changed structure of layers plating, friction and wear characteristic of hard chrome plating became better. Hard chrome coated tool steel substrate of AISI 4140 type was nitridised (550oC, 4 hours of boost phase and 2 hours of diffusion phase) without gas diffusion media. The analysis of AFM shows the roughness value of the surface was increase after the treatment of nitriding. The nodular structure would provide width of oil storage as greater self lubricant. The structure formed can be illustrated like an area of farm. The structure could also omit the jagged area. The mechanism of nitrogen atom deposition that is interesting and relatively new was observed in this research as well.

Friction Stir Welding on Corner Joint with New Surface Preparation Design

Aluminium 6061 was joined by friction stir welding (FSW) with new surface preparation on corner design. The distribution micro structure in Corner-joints was tool welded rotation (rpm), and travel speed (mm/mnt) observed and analyzed. The welding parameters observing the tensile strength, micro structure and micro hardness it can be said. The result structure micro are homogen whilst from tensile test the strength joint is quilt good even better from preview publihsed papers. The obtained with the transverse speed 15 mm/menit, and 1500 rpm.