The Influence of Oxidizing Parameters on the Formation of Oxide Layer as a Precursor for the Fabrication of Carbon Fiber-Steel

Universiti Teknologi PETRONAS in partial fulfillment of the requirement for the Bachelor of Mechanical Engineering with Honours. Based on the Taguchi's analysis and XRD results, run number nine has the optimal stable oxide formation parameters where high temperature, surface roughness and time yield higher oxidation with magnetite content on the surface of the carbon steel.

PROBLEM STATEMENT

In industry, FMLs are commonly used in the aircraft industry due to their high performance and lightweight structure. That is where the strong development of these fiber-metal laminate structures started, where Aramid Reinforced Aluminum Laminate (ARALL), Carbon Reinforced Laminate (CARALL) and Glass Reinforced Aluminum Laminate (GLARE) have been implemented in this industry [9]. Some of the industries include the construction industry where carbon fiber reinforced polymer (CFRP) is used in reinforcing the concrete beams and FML is used in the offshore and marine industries such as improvising stealth hull technologies and online pipe repairs being caused by galvanic corrosion.

OBJECTIVES

SCOPE OF STUDY

Using Taguchi's design of experiment with statistical orthogonal array arrangement to obtain different combinations of sample preparation parameters. By using X-Ray Diffraction (XRD) to analyze the percentage of stable oxide form on the surface and verify the percentage of formation with the statistical study.

LITERATURE REVIEW AND THEORY

OVERVIEW OF CARBON STEEL

The formation of oxide on the surface of the steel consumes the iron element on the carbon steel causing the steel to reduce or corrode. Fe + 4 Fe2O3 ↔ Fe3O4 Fe (2) Where the presence of hematite on the surface of the steel is such that due to the presence of water the hematite reduces with the iron metal.

Figure 2.1: Iron Oxide Phase Diagram [17]

INVESTIGATION OF THE OXIDIZING PARAMETERS

Different time and temperature can provide different reaction rates to the oxidation process on the steel surface. The longer the exposure to the high temperature of the oxidizing environment, the thicker the oxide layer is formed and the wustite layer can fully develop as the surface is allowed for the reaction to fully propagate. As important as time and temperature in the formation of the various oxide layers, the rate of heating also affects the rate of oxidation on the steel surface.

When the heating rate reaches the peak temperature, the rate is kept at a constant temperature, where the phase changes can normally occur evenly on the surface of. Despite this, high heating rate can cause unstable growth of the particles due to attaching kinetics of the particles, which can affect the formation of oxide films on the surface of the steel varying in the thickness of the film and the type of oxide formed. One of the key parameters that will affect the formation of oxide layers is the surface roughness of the steel.

Higher surface roughness produces thicker oxide films as the contact of oxygen with the surface of the metal varies instead of smoother surface where the contact is almost constant throughout the entire surface of the steel. Carbon fiber reinforced composite maintains a high specific strength, the carbon composites are twice as strong as steel, and by combining, the required strength of the steel is achieved without increasing the composition and density of steel, thus reducing the weight by half [24]. One way to reduce the occurrence of the galvanic corrosion is by the formation of a protective stable oxide layer, which acts as a passivation on the surface of the metal [24].

Figure 2.3: Graphical representation of oxide layer thickness (µm) for all evaluated samples [21]

METHODOLOGY

• OVERALL PROJECT PROCESS FLOWCHART
• DESIGN OF EXPERIMENT USING TAGUCHI’S METHOD
• EXPERIMENTAL PROCEDURE
• EQUIPMENT AND MATERIAL

Since there are different standards for orthogonal arrays, each of the arrays depends on the specific number of independent design parameters and levels. In the first part of the study of the oxidizing parameter of carbon steel was the formation of oxides on the carbon steel. Moreover, the lowest time is set based on the minimum requirement of the normalizing furnace at Block 17, Universiti Teknologi PETRONAS.

The heating rate is set according to the correct setting of the normalization furnace in block. Finally, the roughness of the sandpaper used for sample preparation was based on the formation of oxide at different surface roughnesses of Zircaloy-4 [22]. In the experimental procedure, the oxidized steel is prepared based on the Taguchi experiment design, and a microhardness test is performed to be used as a performance parameter in the evaluation of stable oxide in the experiment design.

The formation of oxide is performed by heating the surface prepared carbon steel which is placed in the normalization furnace with temperature, time and heating rate for the samples based on the designed experimental setup using the orthogonal array. The setting in the furnace is made to follow the oxidation cycle for each process, based on the combination of the three heat parameter, as shown in Figure 3.4. As for this research, the Vickers hardness tests are performed on the surface of the oxidized steel.

After the nine experiments have been performed based on Taguchi's experiment design, the average hardness value for each of the experiments is evaluated using the signal-to-noise ratio (S/N). Based on the optimization performed using the ANOVA method to determine the best parameter to obtain a high hardness value.

Table 3.1: Comparison of Factorial Design and Taguchi’s Method of Number of Experiment

RESULTS AND DISCUSSION

PHYSICAL OBSERVATION OF SAMPLE TRANSFORMATION

Therefore, in the first eight experiments, the unstable oxide is present and can be clearly observed, and no visible unstable oxide is visible in the last experiment, making it a more passive oxide on the surface. From a physical point of view, it can be deduced that oxide formation varies with each temperature level, mainly because a higher browning occurs in the first three samples oxidized at 400oC, followed by the fourth through sixth samples oxidized at 600oC .

MICROHARDNESS TEST RESULT FOR DETERMINING THE SIGNIFICANCE OF THE PARAMETER AND LEVEL

Based on the microhardness test, it can be observed that the oxidized steel has a higher hardness compared to bare steel. In addition, experiment number nine yields the highest average hardness value among the other experiments. Using equation (5), the S/N ratio of each experiment and the mean S/N ratio value can be calculated and tabulated as shown in Table 4.2.

Table 4.1: Average hardness value for bare steel and oxidized steel for each experiment run

EFFECT OF HARDNESS ON THE SIGNIFICANCE OF EACH PARAMETER

EFFECT OF TEMPERATURE ON AVERAGE HARDNESS OF OXIDIZED

STEEL

Figure 4.3 shows the effect of temperature on the formation of iron oxide based on the effect of temperature on the hardness. From the graph it can be deduced that the higher the temperature, the higher the average hardness of the sample. Figure 4.4 shows the effect of time on the formation of iron oxide based on the effect of time on the hardness.

The graph shows that the increase in time in the oxidation of the sample increases the hardness of the sample.

EFFECT OF TIME ON AVERAGE HARDNESS OF OXIDIZED STEEL

EFFECT OF HEATING RATE ON AVERAGE HARDNESS OF OXIDIZED STEEL

Figure 4.5 shows the effect of heating rate on iron oxide formation based on the effect of heating rate on hardness. From the graph, based on the average signal-to-noise stiffness, it can be deduced that the heating rate does not significantly affect the stiffness of the sample. The peak hardness is when the heating rate is set at 15oC/min and the higher heating rate shows a much greater decrease in hardness than the lower heating rate.

Surface roughness affects hardness inversely from the other parameters, so that a smoother surface, which is the highest grain, has a lower hardness value.

EFFECT OF SURFACE ROUGHNESS ON AVERAGE HARDNESS OF OXIDIZED STEEL

Based on the analysis of variance (ANOVA), the determination of the percentage contribution of each parameter in the study can be made using the S/N ratio of each factor, thus elucidating the combinatorial effect of mean hardness on oxide formation. certain.

Combinatorial Effect of Oxide Formation

XRD ANALYSIS ON THE FORMATION OF OXIDE ON CARBON STEEL The X-Ray Diffraction analytical method was used to obtain and compare the different

From the nine experiments that have been carried out, the XRD analysis was carried out to verify the formation of iron oxides on the surface of the oxidized steel and determine the sample with the greatest formation of magnetite. Based on the XRD analysis for all nine test runs, run number eight and run number nine are the only ones with wustite content on the oxidized steel. Based on the XRD results obtained on the nine trials run, it can be confirmed that each trial run has iron oxides on the carbon steel.

According to the formation of iron oxides, hematite (Fe2O3) and magnetite (Fe3O4) are present in all nine experiments. It is also observed that there are some matching wustite formation peaks in experiment number eight and nine. In addition, according to XRD analysis, experimental setup number nine has the highest percentage of magnetite formed on the sample, which is a stable oxide, compared to the other eight, which are dominated by the presence of hematite.

Figure 4.8: XRD result on sample number 1 b)

CONCLUSION AND RECOMMENDATION

CONCLUSION

The stable oxide formed from the parametric study should be further validated by laminating it with carbon fiber reinforced polymer and comparing it with the time of lamination of bare carbon steel with carbon fiber reinforced polymer with mechanical tests such as the impact test and corrosion test of the bonding surface between the carbon fiber and the substrate. Microstructure analysis should be performed on the experimental samples to demonstrate the interaction of the oxides with the steel substrate.

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