This study investigates the impact of arc length, current intensity, travel speed, and gas flow rate on surface hardness and line width during arc quenching process of S45C steel. The current intensity has the greatest influence on the surface hardness of S45C steel, followed by the travel speed, gas flow rate, and arc length. Using the Taguchi method, the optimal values of the parameters such as the arc length of 1.5 mm, the current intensity of 125 A, the travel speed of 250 mm/min and the gas flow rate of 12.5 l/min were calculated. The optimal surface hardness would be 379 HV, with a standard deviation of 46.4 HV. The current intensity is the most critical component in determining line width among these parameters. The arc length ranks second, followed by the TIG gun’s travel speed. The gas flow rate is the least significant factor. A longer arc length may result in a broader heat zone, which leads to a better line width. Increasing the arc length, current intensity, travel speed, and gas flow rate results in a similar pattern of surface hardness change caused by the low-heated and over-heated phenomena. The microhardness distribution showed a hardening zone of up to 2500 μm and a maximum hardness of 453 HV. The microstructure of arc quenching samples has three zones: hardening, heat-affected, and base metal. The hardening zone exhibits a martensite microstructure with a tiny needle shape and a residual austenite matrix.

Arc quenching has many advantages, including generating large amounts of heat in a short time, a self-quenching ability, and simple equipment. The electric arc energy from a TIG welding machine was used to modify the surface properties of S45C Carbon Steel Cylinders. The study focuses on the impact of arc length, current intensity, travel speed, gas flow rate, heating angle, and pulse on surface hardness after arc quenching an S45C steel tube with a cylinder surface. The study found that the hardness reduces from 45.1 HRC to 41.2 HRC as the current intensity increases from 125 A to 140 A. According to Taguchi’s results, the ranking of factors which have the greatest impact on surface hardness are pulse time, travel speed, intensity, gas flow rate, arc length, and heating angle. The pulse time has the highest impact because it directly influences the heating input, followed by the travel speed. Arc length and heating angle, on the other hand, have the least effect. The base metal, heat-affected area, and hardened area are the three distinct areas that make up the microstructure structure. After the arc quenching process, the case hardening depth is represented by the heat-affected zone at 1536 μm. A highly colored residual austenite and a needle-shaped martensite phase make up the hardened region. The hardened region is 1200 μm thick and has a hardness of more than 300 HV0.3. The study’s findings may improve the application and understanding of the arc quenching treatment procedure in the industrial sector.

This study investigates the effects of arc length, current intensity, travel speed, gas flow rate, and pulse time on surface hardness to better understand the arc quenching of S45C steel with a curved shape. With the standard examination method, increasing the current intensity, Travel speed, and arc length causes the surface hardness to decrease. The surface hardness varies depending on the gas flow rate and pulse time. The Travel speed factor appears to have the greatest effect, followed by the gas flow rate and current intensity. Pulse time and arc length are ranked fourth and fifth, respectively, indicating a smaller impact on surface hardness. The microhardness diagram is divided into four stages: improving, rapid dropping, moderate dropping, and stable. The greatest hardness was 576 HV, with a case depth of 1200 μm. The structure of the arc-hardened sample is composed of hardening zones, HAZ, and base metal. The base metal is composed of ferrite and pearlite, which are the original microstructures of medium-carbon steel. The HAZ is made up of two phases: a brown bainite phase and a brighter ferrite phase. Ferrite, bainite, martensite, and residual austenite phases make up the hardening with a high hardness value area. These phases’ diversity results from their rapid heating and cooling rates as well as the significant variations in cooling rates among depths. The findings of the study on the optimum values of factors such as current intensity at 150 A, Travel speed at 150 mm/min, arc length at 2.5 mm, pulse time at 0.6 s, or gas flow at 10.5 l/min can help engineers to have a closer look at the parameters of this arc tempering technology affecting the surface hardness and their applications. Moreover, the hardness measurement value according to the Taguchi method investigation also shows that the highest value of surface hardness achieved is 42.6 HRC compared to 18 HRC of unhardened surface hardness. In addition, the findings on microstructure also help the applicator to better understand and evaluate the quality of this electric arc method for quenching the surface of S45C steel, thereby making it more useful in the industry.

This study investigates the impact of arc-hardening parameters on a groove-shaped S45C steel tube, with a focus on surface hardness and microstructure. According to the findings, when arc quenching occurs, the tube’s surface hardness increases significantly compared to its original hardness. The surface layer hardness can increase to 50.3 HRC, which is 3.4 times greater than the untreated surface. Changing arc quenching parameters such as current intensity, gas flow rate, arc length, scan speed, heating angle, and cooling angle causes a variation in surface hardness due to the balance of heat input and cooling value. Moreover, the microhardness distribution is divided into three zones: the hardened zone (with a high hardness value), the heat-affected zone (HAZ), which has rapidly declining hardness, and the base metal (with a low hardness value). The hardened zone could have a hardness with a load of 0.3 N of 440 HV and a case depth of about 900 μm. The next zone is the HAZ, where the hardness with a load of 0.3 N drops significantly. The hardness in the base metal zone recovers to its original value of 152 HV. Interestingly, the microstructure, under the hardness distribution, illustrates the relationship between the hardness value and its phases. The hardened zone consists of martensite and residual austenite phases, resulting in a high hardness value. The bainite phase constitutes the HAZ, which correlates to the zone of rapid hardness reduction. Finally, the base metal zone has ferrite and pearlite microstructures, indicating the softest zone. The investigation’s findings may increase our understanding of the arc-hardening process and widen its industrial applications.

This work investigates the surface hardness after arc quenching S45C steel with a convex surface, including arc length, current intensity, travel speed, gas flow rate, and the pulse duration. The surface hardness is mostly determined by the intensity of the current. Interestingly, the convex surface shows an impressive 108% increasing from its initial hardness of 182 HV. Increased heat input at high current intensity may be the cause of the overheating and melting phenomena as well as the decreased hardness. Surface hardness generally increases with increases in gas flow rate, resulting from an enhanced gas cooling rate. Similar to the gas flow rate, surface hardness rises with TIG gun travel speed. In addition, the convex surface hardness's Taguchi prediction value is 359.6 HV. The ideal parameters are 90 A for the current intensity, 2.5 mm for the arc length, 12 l/min for the gas flow rate, 200 mm/min for the travel speed, and 0.7 s for the pulse duration. In addition, 3D surface plots were also used to evaluate the degree of interaction between parameters with each other. For the S45C convex surface, the maximum case depth of the arc quenching is 3500 µm. The hardened area, the heat-affected area, and the base substrate are the three regions of the arc quenching sample's microstructure.