IMPROVED REPRODUCIBILITY OF D2 TOOL STEEL AFTER CRYO-TREATING AT -78°C (DRY ICE)

The exposure of steel to very cold temperatures (cryogenics) as a means to improve properties of the metal has had a controversial history. This study employed several tests to determine differences between D2 tool steel cryo-treated in dry ice (-78°C) versus in liquid nitrogen (-196°C), as compared to control D2 steel (not cryo-treated). These tests showed no major changes between the control and the liquid nitrogen treated steel, but the dry ice (-78°C) treated steel showed narrower XRD peaks, more reproducible hardness measurements, less scatter in the corrosion weight loss, and lower corrosion currents in the cyclic polarization tests in saltwater. All these differences were measured even though there was no measurable difference in retained austenite. The authors hypothesize that the -78°C (dry ice) allowed internal stress reductions, while the -196°C (liquid nitrogen) was too cold to allow any transformations.

USING ONE OF ORGANIC EXTRACTS AS A CORROSION INHIBITOR FOR CARBON STEEL IN ACIDIC ENVIRONMENT

Utilization of mangosteen rind extract as carbon steel inhibitors in the environment of hydrochloric acid (HCl) 0.1M, 0.5M, and 1.0M. Extracts were carried out by extraction using ethanol solvent at a temperature of 600C with a time of 80 minutes. The variation of extract concentration (100 ppm to 1000 ppm in 3 days and the effect of time of corroding the carbon steel with the addition of 1000 ppm extract. Corrosion rate is calculated based on the difference in weight and corrosion products shown by microscope optics. The objective was investigated corrosion inhibition efficiency that could be prevented by mangosteen peel extract as inhibitor. The results showed inhibitory properties of mangosteen peel extract for three (3) days increased with increasing extract concentrations up to 76.53% in 0.1M HCl solution and 28.83% in 1.0M HCl solutions. For the addition of 1000 ppm mangosteen peel extract showed inhibitor efficiency reached about 90% at 3 days of corrosive time in HCl 0, 5 M, 87% in 1.0 M HCl solution, and 81% in 0.1 M HCl solution. The experiment showed that the process of diffusion of compounds in extracts on the surface of carbon steel and react with ferro ions (Fe2 +) to form chemical covalent coordination coordinate with a thickness of 76 µm was successfully done.

CRYSTALLIZATION PROCESSES OF SOME AMORPHOUS ALLOYS

A series of Fe40Co40Zr8M2B10 (M=Nb, V, Cr, Ti, W, Al) alloys were prepared using melt-spinning. The thermal curve, structure and magnetic property of alloys are examined. Because of different negative heat of mixing between elements, only Fe40Co40Zr8M2B10 (M=Nb, V, Cr, Ti) alloys form amorphous structure. These amorphous alloys are annealed at different temperatures under vacuum conditions. The crystallization processes of four amorphous alloys are similar. In the primary stage of crystallization process, only α-Fe (Co) phase precipitates and Co element mainly distributes in the residual amorphous. For the four alloys after annealing at 550°C, there is a few differences in saturation magnetization (Ms) and coercivity (Hc) due to their different microstructures.

CORROSION BEHAVIOR OF STEEL IN ACIDIC MEDIUM FOR PETROLEUM SYSTEMS

The electrochemical reaction response of austenitic 316L stainless steel and carbon steel was examined through weight loss analysis in 1M, 2M and 3M of HCl acid. The results show that austenitic 316L has high corrosion resistance than carbon steel for the test analyzed with the lowest corrosion rate of 0.0018mm/y at 1M of HCl and highest at 0.0053mm/y when compared with carbon steel which has the lowest corrosion rate of 0.0003mm/y for 1M of HCl and highest at 0.0013 mm/y of 3M of HCl solution all at ambient temperature conditions. General corrosion was displayed on the surface of the carbon steel but austenitic 316L was not affected due to the presence of chromium alloy and other alloying elements.

USING WIRE BEAM ELECTRODE (WBE) TO EVALUATE THE CORROSION BEHAVIOR OF ND STEEL IN ACID MEDIUM

In this article, wire beam electrode (WBE) was used to evaluate the corrosion behavior of ND steel in environmental acid atmosphere with different partial pressure of CO2. Meanwhile, corrosion products and surface morphology analysis also used to support this research. The results showed that the corrosion behavior began from the edge of droplet in dew point corrosion, and gradually spread to the center of it. The spread speed would be increasing with CO2 partial pressure enhance, which was 24h in 5% CO2 and 4h in 50% CO2. Corrosion current density in the edge of droplet can form the “cathode-anode-cathode ring” structure and disappears gradually as the corrosion time was going. Corrosion morphology observation results showed three ring shapes region and different elemental composition of different corrosion products, which is correspondence with the “cathode-anode We-cathode ring” structure measured in WBE experiments. The results showed that the reaction gradually transferred to the uniform corrosion on electrode surface when the dew point corrosion reaction reaching the late stage. It comes from the dissolution, diffusion and reaction of gaseous corrosion medium of CO2 and O2.

EXPECTING OF CORROSION RATE IN A MATERIAL AFFECTED BY DIFFERENCES SOIL TYPE IN CONTROLLED ENVIRONMENTS.

Research has been done on corrosion rates growth in SA 283 material which is influenced by differences in soil types in controlled environments. A283 grade D materials which are carbon steel formed into pipes with a diameter of 30″ which is used to distribute raw water for industrial needs. Weight loss methods that are in accordance with the ASTM G 162 standard have been used in this study. The buried time of the test specimen is 720 hours as one of the variables in calculating the value of the corrosion rate that occurs. The study was conducted at the Laboratory by controlling the soil structure, reducing potential, moisture level, soil pH level so that it did not change. The results of the study on soil types with a potential redox value of 60.6 mV with a pH level of 5.67 showed the greatest corrosion rate in material A283 that is 19.67 MPY or equal to 0.499 mm/yr. The results of this study concluded that the type of soil and its environment greatly affect the corrosion rate of carbon steel, so special attention is needed in protecting the pipe from corrosion attack.

EFFECT OF MAGNESIUM FLUORIDE COATING ON CORROSION BEHAVIOR OF MAGNESIUM ALLOY

Magnesium and its alloys are explored as potential biomedical materials for being lightweight, bio-absorbable, and having attractive biological properties. A major hindrance for their use is their high corrosion rate, in particular when exposed to body fluids. This study aims at suppressing the corrosion rate of a magnesium alloy (Mg1.0Ca) by coating it with magnesium fluoride (MgF2). The coating was done by immersion of the work-piece in hydrofluoric acid solution. For comparison, pure magnesium was also coated with MgF2. The MgF2 coated magnesium exhibits significantly lower corrosion rate than pure magnesium. The MgF2 coated magnesium alloy shows even lower corrosion rate. The MgF2 coating works in inhibiting corrosion on magnesium alloy Mg1.0Ca. The corrosion inhibition was also contributed by other compound formed during reaction between Mg1.0Ca and hydrofluoric acid and the alloy in Mg1.0Ca.

USING GEOPOLYMER COMPOSITES FOR HEAT AND CORROSION RESISTANT PIPES

This research studied the use of carbon fiber reinforced geopolymer composites as corrosion resistant pipe material. Geopolymer material is a general term for material synthesized from fly ash. Fly ash is an industrial by-product (coal combustion residue) with high silica content (SiO2) and Alumina content (Al2O3). In addition, there are also other elements in a relatively small percentage. This material will compound like cement if activated with Sodium Silicate. This study aims to obtain the optimum composition for high quality mechanical properties. The method used is to synthesize material with various elemental compositions. Furthermore, a mechanical test (bending test) is performed to see the effect of each element to be optimized. Besides that, a physical test in the form of SEM-EDX was also conducted to see the microstructure. Materials with optimum composition have been fabricated as pipes with centrifugal casting process. Mechanical testing of pipe samples is done by hoop tensile strength test. The test results show that the strength of geopolymer composites can achieve 58 MPa.

EFFECT OF MAGNESIUM FLUORIDE COATING ON CORROSION BEHAVIOR OF MAGNESIUM ALLOY

Magnesium and its alloys are explored as potential biomedical materials for being lightweight, bio-absorbable, and having attractive biological properties. A major hindrance for their use is their high corrosion rate, in particular when exposed to body fluids. This study aims at suppressing the corrosion rate of a magnesium alloy (Mg1.0Ca) by coating it with magnesium fluoride (MgF2). The coating was done by immersion of the work-piece in hydrofluoric acid solution. For comparison, pure magnesium was also coated with MgF2. The MgF2 coated magnesium exhibits significantly lower corrosion rate than pure magnesium. The MgF2 coated magnesium alloy shows even lower corrosion rate. The MgF2 coating works in inhibiting corrosion on magnesium alloy Mg1.0Ca. The corrosion inhibition was also contributed by other compound formed during reaction between Mg1.0Ca and hydrofluoric acid and the alloy in Mg1.0Ca.

CONSTITUTIVE MODELING OF DYNAMIC RECRYSTALLIZATION AND PRECIPITATION BEHAVIOR OF Nb AND Ti OF Q1030 HIGH STRENGTH STEEL

The thermal deformation and precipitation behavior at 900-1100℃ and strain rate of 0.1-5s-1 were studied by Gleeble-3800 thermal simulator of Q1030 high strength steel. The activation energy of hot deformation in austenite region was determined by regression method, and the hot deformation equation of the Q1030 high strength steel was established. The critical strain and peak strain of dynamic recrystallization were predicted accurately by fitting the inflection point with cubic polynomial of curve of Q1030 high strength steel, and relationship between critical strain and Z parameter was established. Finally, the precipitation behavior of Nb and Ti particles during low strain rate deformation was studied, the results show that the precipitated phases in steel are rectangular TiN, quadratic (Nb, Ti) (C, N) carbonitride, elliptical (Nb, Ti) C carbide and NbC. Thermodynamic calculation shows that the order of precipitation of the second phase in steel is TiN, TiC, NbC and NbN.