Mechanical Investigations of ASTM A36 Welded Steels with Stainless Steel Cladding

The in-service life of ASTM A36 welded steel pipes in power plants is often shortened by ash corrosion. During the heating condition, the ash deposition on the welded steel pipes gradually reduces the thickness of the pipes, thus, reducing the lifetime. Instead of replacing the pipes with new ones, the cost could be significantly reduced if the lifetime could be further extended. Weld cladding was the method selected in this study to temporarily extend the service life of welded pipes. This paper performed the mechanical investigations of A36—A36 welded steel plates after coating the surfaces with 309L stainless steel with a cladding method. The residual stress was also tested to observe the internal stresses developed during the welding processes of A36—A36 specimens. The comparison between the coated and non-coated surfaces of welded steels was performed by using the tensile tests (at room and elevated temperatures), corrosion (pitting corrosion, intergranular corrosion, and weight-loss corrosion) tests, and wear (shot blasting) tests. The life-extension of both coatings was evaluated based on the tensile tests and the corrosion and wear tests provided the qualitative evaluations of the coating performance. The results showed that surfaces coated by cladding could be used to temporarily extend the life of ASTM A36 welded steel under the studied conditions.


Introduction
ASTM A36 is a carbon structural steel generally used in welded constructions and power plants [1]. In coal-fired and biogas power plants, ash can deposit on steel surfaces and cause severe corrosion [2,3]. Under cyclic thermal conditions coupled with ash corrosion, the lifetime of these structural components is significantly reduced [4], and one of the main reasons is the thickness reduction or weight loss on steel surfaces [5]. The corrosion consequences can lead to component failures, safety and environment hazards, downtime, and high maintenance costs. One of the standard techniques to prevent such failures or extend the lifetime is surface coating [6]. Stainless steels have been widely coated on and environment hazards, downtime, and high maintenance costs. One of the standard techniques to prevent such failures or extend the lifetime is surface coating [6]. Stainless steels have been widely coated on their surfaces in many applications and conditions due to the resulting superior microstructural and mechanical properties [7][8][9][10][11][12][13][14][15][16].
Since many structural components in power plants are welded together, the stainless steel cladding overlays on welded steel joints is a significant concern and must be well understood [51]. One research study found that a two-layer weld overlay was recommended to achieve better corrosion resistance [52]. Different overlay coatings and processes were also investigated to observe the interface bonding metallurgy and strengths [53]. Hardness and tensile tests were also performed to observe the stainless steel coating on steel welds [54]. Nevertheless, it is still unclear if welded steel joints overlayed with stainless steel coatings would survive and perform under the operating conditions. This study aimed to investigate the mechanical properties of the stainless steel cladding surfaces of steel welds. Note that purpose of the addition of cladding was only to temporarily extend the lifetime of the welded components, which could significantly save power plants' downtime costs. However, the coated surfaces must also work under the required conditions without failures. As a result, tensile tests were carried to observe the bonding interfaces' strengths at room and elevated temperatures. Corrosion and wear tests were also performed to determine if these cladding surfaces could withstand corrosive environments.

Weld Materials Preparation
The scope of this research was to investigate the extended lifetime of the A36-A36 welded joint by coating its surface by cladding it with 309L stainless steel. The substrate workpiece was prepared by welding two ASTM A36 plates together, as shown in Figure 1.   Before welding, two A36 plates were pre-heated at 148 • C to avoid recrystallization, which could lead to hydrogen-induced cracking. The first two layers were welded by gas tungsten arc welding (GTAW) with 99.9% argon shielding gas, and layers 3 to 13 were joined by using shielded metal arc welding (SMAW). Note that the weld groove angle in the SMAW process was 75 • with a 3 mm root height and a 3 mm root gap. The specific conditions of the two welding processes are listed in Table 1. The chemical and mechanical properties of the substrate and filler materials used in the welding processes are described in Tables 2 and 3, respectively.   The welded plate's macrostructure was then examined to determine the weld quality, as illustrated in Figure 2. Three main zones could be observed in the cross-section of the A36-A36 weldment: base, heat affected zone (HAZ), and weld metal.

Cladding Process and Residual Stress Measurements
The welded plate was then coated by cladding its surface with 309L stainless steel (E309L-16), as demonstrated in Figure 3.

Cladding Process and Residual Stress Measurements
The welded plate was then coated by cladding its surface with 309L stainless steel (E309L-16), as demonstrated in Figure 3.

Cladding Process and Residual Stress Measurements
The welded plate was then coated by cladding its surface with 309L stainless steel (E309L-16), as demonstrated in Figure 3. SMAW was carried out to create a hard-facing overlay of 2.8-3.0 mm. Note that the cladding direction was perpendicular to the weld direction or A36-A36 weldment. The detailed information about the SMAW process is described in Table 4. After the entire surface was coated with 309L stainless steel, the top surface (overlay) was ground to have approximately 2.8 mm thickness.  SMAW was carried out to create a hard-facing overlay of 2.8-3.0 mm. Note that the cladding direction was perpendicular to the weld direction or A36-A36 weldment. The detailed information about the SMAW process is described in Table 4. After the entire surface was coated with 309L stainless steel, the top surface (overlay) was ground to have approximately 2.8 mm thickness. The residual stress measurements were carried out on the welded plates both before and after cladding to evaluate the internal stresses that resulted from the welding processes. A non-contact surface scanner (µ-X360s Portable X-ray Residual Stress Analyzer by PULSTEC, Hamamatsu, Japan) was used to measure the residual stress. Figure 4 displays the measurement locations (B1 to B9, and A1 to A4). Before the cladding, the residual stresses in all three zones (base, HAZ, and weld metal) were measured ( Figure 4a). However, the residual stresses were checked in only the HAZ and weld metal zones of the cladding surface because these zones were vulnerable to heat.

Tensile Tests
Since the coated plate's service life depended on its mechanical strength, each layer of cladding workpiece was extracted and tested by the tensile test, as described in Table 5, to determine its strength at elevated temperatures. Figure 5 shows the locations of the tensile testing specimens that were machined out of the cladding surface and substrate. The specimens in the cladding layer were cut into flat samples having a 50 mm gauge length and 12.5 mm width. The substrate specimens were machined into rod specimens with a 50 mm gauge length and 8.0 mm diameter. The Instron 1000 HDX machine ((Instron, Norwood, MA, USA) was used to carry out the tensile tests, and the pulling speed was 5 mm/min. Note that the tensile testing procedure followed the ASTM E8 standard [55].
The residual stress measurements were carried out on the welded plates both before and after cladding to evaluate the internal stresses that resulted from the welding processes. A non-contact surface scanner (μ-X360s Portable X-ray Residual Stress Analyzer by PULSTEC, Hamamatsu, Japan) was used to measure the residual stress. Figure 4 displays the measurement locations (B1 to B9, and A1 to A4). Before the cladding, the residual stresses in all three zones (base, HAZ, and weld metal) were measured (Figure 4a). However, the residual stresses were checked in only the HAZ and weld metal zones of the cladding surface because these zones were vulnerable to heat.

Tensile Tests
Since the coated plate's service life depended on its mechanical strength, each layer of cladding workpiece was extracted and tested by the tensile test, as described in Table 5, to determine its strength at elevated temperatures. Figure 5 shows the locations of the tensile testing specimens that were machined out of the cladding surface and substrate. The specimens in the cladding layer were cut into flat samples having a 50 mm gauge length and 12.5 mm width. The substrate specimens were machined into rod specimens with a 50 mm gauge length and 8.0 mm diameter. The Instron 1000 HDX machine ((Instron, Norwood, MA, US) was used to carry out the tensile tests, and the pulling speed was 5 mm/min. Note that the tensile testing procedure followed the ASTM E8 standard [55].

Corrosion Tests
Since the actual operating conditions were significantly affected by corrosion, three major    In the pitting corrosion tests, the specimens were cut to 25 mm along the weld and 50 mm across the weld. Prior to the test, all surfaces of the samples were ground wet by 120-grit polishing. Pickling was performed for 5 min at 60 °C in a solution of 20% HNO3 and 5% HF. The specimens were cleaned by rinsing with water, then dipping in acetone, and being air-dried. Afterward, the samples were immersed in the 6% FeCl3·6H2O solution at a constant temperature of 50 °C for 24 h. Then specimens were cleaned, and the pitting evaluation was carried out by using the microscope. Figure 7a,b demonstrates the pitting corrosion test setup. Figure 7c,d show the intergranular corrosion tests. Each specimen was machined to be 25 mm (width) by 100 mm (length) to achieve a smooth surface. Prior to or the test, the samples were cleaned with alcohol in the ultrasonic cleaner. In each intergranular corrosion test, a specimen was filled with a layer of copper shot on the bottom of the test flask and immersed in the dissolved 100 g of CuSO4·5H2O in 700 mL of distilled water. Then, 100 mL of sulfuric acid was added and filled with distilled water to acquire 1000 mL test solutions. The specimen in the test solution was then boiled In the pitting corrosion tests, the specimens were cut to 25 mm along the weld and 50 mm across the weld. Prior to the test, all surfaces of the samples were ground wet by 120-grit polishing. Pickling was performed for 5 min at 60 • C in a solution of 20% HNO 3 and 5% HF. The specimens were cleaned by rinsing with water, then dipping in acetone, and being air-dried. Afterward, the samples were immersed in the 6% FeCl 3 ·6H 2 O solution at a constant temperature of 50 • C for 24 h. Then specimens were cleaned, and the pitting evaluation was carried out by using the microscope. Figure 7a,b demonstrates the pitting corrosion test setup. Figure 7c,d show the intergranular corrosion tests. Each specimen was machined to be 25 mm (width) by 100 mm (length) to achieve a smooth surface. Prior to or the test, the samples were cleaned with alcohol in the ultrasonic cleaner. In each intergranular corrosion test, a specimen was filled with a layer of copper shot on the bottom of the test flask and immersed in the dissolved 100 g of CuSO 4 ·5H 2 O in 700 mL of distilled water. Then, 100 mL of sulfuric acid was added and filled with distilled water to acquire 1000 mL test solutions. The specimen in the test solution was then boiled for 24 h. Afterward, the specimen was cleaned in the ultrasonic cleaner and was air-dried. The face bend weld test was also carried out by bending the tested sample 180 • over a mandrel with a radius not exceeding the specimen's thickness.
The third corrosion test was to measure the weight loss of the base material (A36 steel) and the cladding layer (309L stainless steel-A36 steel). Each specimen was cut to a 25 mm (width) and 25 mm (length) size. The surface was ground wet by 120-grit and cleaned with alcohol in the ultrasonic cleaner. The specimen was then immersed in the 30% Nital test solution at constant room temperature for 24 h. Then, the sample was cleaned, and the weight loss measurement was performed.

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Coatings 2020, 10, x FOR PEER REVIEW 8 of 19 for 24 h. Afterward, the specimen was cleaned in the ultrasonic cleaner and was air-dried. The face bend weld test was also carried out by bending the tested sample 180° over a mandrel with a radius not exceeding the specimen's thickness. The third corrosion test was to measure the weight loss of the base material (A36 steel) and the cladding layer (309L stainless steel-A36 steel). Each specimen was cut to a 25 mm (width) and 25 mm (length) size. The surface was ground wet by 120-grit and cleaned with alcohol in the ultrasonic cleaner. The specimen was then immersed in the 30% Nital test solution at constant room temperature for 24 h. Then, the sample was cleaned, and the weight loss measurement was performed.

Wear Tests
In the coal-fired power plants, structural systems were typically under worn out by erosion. As a result, a shot blasting experiment was carried out to observe the wear performance of the cladding surfaces, as seen in Figure 8. Two types of specimens were considered here: a substrate (A36-A36 welded plate), and a cladding (309L stainless steel). Each sample was cut to have dimensions of 50 mm in width, 75 mm in length, and 6 mm in thickness. In the shot blasting process, the specimen was placed into the chamber (Figure 7b), and the sands (250-425 μm in diameter) were blasted with 0.6 MPa using a nozzle having 6.25 mm in diameter. Three levels of shot blasting times were carried out (Table 7) and the accumulated weight loss after each time was measured.

Wear Tests
In the coal-fired power plants, structural systems were typically under worn out by erosion. As a result, a shot blasting experiment was carried out to observe the wear performance of the cladding surfaces, as seen in Figure 8. Two types of specimens were considered here: a substrate (A36-A36 welded plate), and a cladding (309L stainless steel). Each sample was cut to have dimensions of 50 mm in width, 75 mm in length, and 6 mm in thickness. In the shot blasting process, the specimen was placed into the chamber (Figure 7b), and the sands (250-425 µm in diameter) were blasted with 0.6 MPa using a nozzle having 6.25 mm in diameter. Three levels of shot blasting times were carried out (Table 7) and the accumulated weight loss after each time was measured.

Results
The results section is divided into three parts, as follows.

Residual Stress Measurement Results
The X-ray diffraction method used here provided the in-plane principal stresses in the weld direction (WD) and the cladding direction (CD), as illustrated in Figure 9. After the A36-A36 plates were welded together, the material within the welded plate started to shrink as it cooled down, and

Results
The results section is divided into three parts, as follows.

Residual Stress Measurement Results
The X-ray diffraction method used here provided the in-plane principal stresses in the weld direction (WD) and the cladding direction (CD), as illustrated in Figure 9. After the A36-A36 plates were welded together, the material within the welded plate started to shrink as it cooled down, and the residual stresses developed. The negative values were compressive stresses, and the positive values were tensile stresses. The high-stress concentration sites should be paid attention to because they could lead to reduced fatigue resistance. Before cladding (Figure 9a,b), the high compressive stress locations were mainly found in the weld metal and HAZ zones in the center area. Figure 9c,d shows the residual stress distributions in the concerned areas (weld metal and HAZ) after cladding. Since the X-ray diffraction measurement depth was shallow, the residual stresses after cladding were mainly caused by the hard facing overlay (309L stainless steel). The overall stress distribution was considered typical and would not lead to lower fatigue resistance.

Results
The results section is divided into three parts, as follows.

Residual Stress Measurement Results
The X-ray diffraction method used here provided the in-plane principal stresses in the weld direction (WD) and the cladding direction (CD), as illustrated in Figure 9. After the A36-A36 plates were welded together, the material within the welded plate started to shrink as it cooled down, and the residual stresses developed. The negative values were compressive stresses, and the positive values were tensile stresses. The high-stress concentration sites should be paid attention to because they could lead to reduced fatigue resistance. Before cladding (Figure 9a,b), the high compressive stress locations were mainly found in the weld metal and HAZ zones in the center area. Figure 9c,d shows the residual stress distributions in the concerned areas (weld metal and HAZ) after cladding. Since the X-ray diffraction measurement depth was shallow, the residual stresses after cladding were mainly caused by the hard facing overlay (309L stainless steel). The overall stress distribution was considered typical and would not lead to lower fatigue resistance.

Tensile Testing Results
The stress-strain plots of the tensile tests are presented in Figure 10. The strengths of the cladding layers (flat specimens) are shown in Figure 10a, and those of the substrate layers (rod specimens) are displayed in Figure 10b.
At room temperature, the cladding layer (CD11-25) having 309L stainless steel (2.5 mm) and A36 steel (2.5 mm) offered the highest tensile strength (548 MPa) and elongation (37%). The addition of A36 steel thickness to 5.0 mm in CD12-25 provided slightly less tensile strength (540 MPa) and the same elongation. Only the 309L stainless steel layer in WD-25 provided lower tensile strength (522 MPa) and much lower elongation (6%). However, the cladding layer having only 309L stainless steel (WD-500) provided the highest tensile strength (376 MPa) and lowest elongation (26%) in comparison to the other cases at 500 • C. The cladding layer (CD11-500) having the same ratio of 309L stainless steel and A36 steel had a higher tensile strength (333 MPa) and slightly lower elongation (34%) than that of the case (CD12-500) having the ratio of 309L stainless to A36 steel of 1:2, which had a 306 MPa tensile strength and 37% elongation.
In Figure 10b, the tensile strength of the base material (SB-500) was 238 MPa with a 40% elongation. The tensile strength of the A36 welded plate (SW-500) provided a tensile strength of 288 MPa. Note that this condition's elongation was very low since the sample was notched at the weld area to force breaking at low strain. The increased strength of the A36-A36 welded plate was still lower than the Coatings 2020, 10, 844 9 of 17 strengths of those with cladding layers in Figure 10a. Also, it could be observed that the addition of 2.5 mm 309L stainless steel to A36 substrate (CD11-550) could increase the tensile strength up to 16% at 500 • C in comparison with the A36-A36 welded plate (SW-500).

Tensile Testing Results
The stress-strain plots of the tensile tests are presented in Figure 10. The strengths of the cladding layers (flat specimens) are shown in Figure 10a, and those of the substrate layers (rod specimens) are displayed in Figure 10b. At room temperature, the cladding layer (CD11-25) having 309L stainless steel (2.5 mm) and A36 steel (2.5 mm) offered the highest tensile strength (548 MPa) and elongation (37%). The addition of A36 steel thickness to 5.0 mm in CD12-25 provided slightly less tensile strength (540 MPa) and the same elongation. Only the 309L stainless steel layer in WD-25 provided lower tensile strength (522 MPa) and much lower elongation (6%). However, the cladding layer having only 309L stainless steel (WD-500) provided the highest tensile strength (376 MPa) and lowest elongation (26%) in comparison to the other cases at 500 °C. The cladding layer (CD11-500) having the same ratio of 309L stainless steel and A36 steel had a higher tensile strength (333 MPa) and slightly lower elongation (34%) than that of the case (CD12-500) having the ratio of 309L stainless to A36 steel of 1:2, which had a 306 MPa tensile strength and 37% elongation.
In Figure 10b, the tensile strength of the base material (SB-500) was 238 MPa with a 40% elongation. The tensile strength of the A36 welded plate (SW-500) provided a tensile strength of 288 MPa. Note that this condition's elongation was very low since the sample was notched at the weld area to force breaking at low strain. The increased strength of the A36-A36 welded plate was still lower than the strengths of those with cladding layers in Figure 10a. Also, it could be observed that the addition of 2.5 mm 309L stainless steel to A36 substrate (CD11-550) could increase the tensile strength up to 16% at 500 °C in comparison with the A36-A36 welded plate (SW-500).

Corrosion Testing Results
The investigated areas (P1 to P4) of the pitting corrosions were observed in Figure 11 to detect if there existed any localized cavities or holes, which could lead to severe corrosion damage. On the cladding sites (P1 and P2), pitting corrosion occurred both on the 309L stainless steel layer. The sampled pitting corrosion sites could be seen in Figure 12, and the dimensions of a pitting site were displayed in Figure 13. These images were taken by using the high-resolution digital microscope (VHX-7000, Keyence, Itasca, IL, USA, 20 to 6000× magnification). Note that rust occurred on the

Corrosion Testing Results
The investigated areas (P1 to P4) of the pitting corrosions were observed in Figure 11 to detect if there existed any localized cavities or holes, which could lead to severe corrosion damage. On the cladding sites (P1 and P2), pitting corrosion occurred both on the 309L stainless steel layer. The sampled pitting corrosion sites could be seen in Figure 12, and the dimensions of a pitting site were displayed in Figure 13. These images were taken by using the high-resolution digital microscope (VHX-7000, Keyence, Itasca, IL, USA, 20 to 6000× magnification). Note that rust occurred on the surfaces shown in Figures 12 and 13 because these samples were rested in the air for an extended period prior to the surface inspection.  At P3 (Figure 11), the localized cavities only appeared on the cladding layer (309L) but could not be observed on the base material side (A36). No pitting corrosions could be observed at P4 even after using the high-resolution digital microscope. As a result, 309L cladding provided pitting corrosion resistance to both the A36 base and A36-A36 weld material because localized corrosion attacks could not penetrate through the cladding layer. These results were consistent with Wang et al.'s that 309L did not corrode in the pitting corrosion tests [58]. At P3 (Figure 11), the localized cavities only appeared on the cladding layer (309L) but could not be observed on the base material side (A36). No pitting corrosions could be observed at P4 even after using the high-resolution digital microscope. As a result, 309L cladding provided pitting corrosion resistance to both the A36 base and A36-A36 weld material because localized corrosion attacks could not penetrate through the cladding layer. These results were consistent with Wang et al.'s that 309L did not corrode in the pitting corrosion tests [58]. Figure 11. The pitting corrosion testing results: (a) Cladding layer over weldment (P1); (b) Cladding layer (P2); (c) Cladding-substrate layer (P3); (d) Substrate layer (P4). Note that all the images were magnified at 20× except those stating "macro". At P3 (Figure 11), the localized cavities only appeared on the cladding layer (309L) but could not be observed on the base material side (A36). No pitting corrosions could be observed at P4 even after using the high-resolution digital microscope. As a result, 309L cladding provided pitting corrosion resistance to both the A36 base and A36-A36 weld material because localized corrosion attacks could not penetrate through the cladding layer. These results were consistent with Wang et al.'s that 309L did not corrode in the pitting corrosion tests [58].   . Figure 13. The measured dimensions of the selected pitting location.
When reheating a welded component, particularly in stainless steel welding, chromium (Cr)rich grain boundary precipitates could lead to a local depletion of Cr adjacent to the precipitates, which could lead to a corrosive attack. In the heat-affected zone (HAZ), titanium or niobium could react with carbon to form carbides, causing intergranular corrosion or the so-called "knife-line" attack because these carbides build-up could not diffuse due to rapid cooling of the weld metal. Figure 14 shows the intergranular corrosion tests' results in the HAZ areas (G1 and G2). Although the A36 base materials seemed to be significantly corroded, no intergranular (carbides build-up) were detected in both locations. As a result, the 309L stainless steel cladding could also be used as a protective layer for intergranular corrosion resistance. When reheating a welded component, particularly in stainless steel welding, chromium (Cr)-rich grain boundary precipitates could lead to a local depletion of Cr adjacent to the precipitates, which could lead to a corrosive attack. In the heat-affected zone (HAZ), titanium or niobium could react with carbon to form carbides, causing intergranular corrosion or the so-called "knife-line" attack because these carbides build-up could not diffuse due to rapid cooling of the weld metal. Figure 14 shows the intergranular corrosion tests' results in the HAZ areas (G1 and G2). Although the A36 base materials seemed to be significantly corroded, no intergranular (carbides build-up) were detected in both locations. As a result, the 309L stainless steel cladding could also be used as a protective layer for intergranular corrosion resistance.
. Figure 13. The measured dimensions of the selected pitting location.
When reheating a welded component, particularly in stainless steel welding, chromium (Cr)rich grain boundary precipitates could lead to a local depletion of Cr adjacent to the precipitates, which could lead to a corrosive attack. In the heat-affected zone (HAZ), titanium or niobium could react with carbon to form carbides, causing intergranular corrosion or the so-called "knife-line" attack because these carbides build-up could not diffuse due to rapid cooling of the weld metal. Figure 14 shows the intergranular corrosion tests' results in the HAZ areas (G1 and G2). Although the A36 base materials seemed to be significantly corroded, no intergranular (carbides build-up) were detected in both locations. As a result, the 309L stainless steel cladding could also be used as a protective layer for intergranular corrosion resistance.   Figure 15 shows the weight-loss corrosion test results observed at the base material (A36) and the cladding material (309L and A36). The observed corrosions seemed to be uniform for both sites (W1 and W2). The calculated weight losses for the A36 plate was 14.51, and 11.11 mg/mm 2 for the cladding layer. The cladding layer could reduce the corrosion weight loss on the A36 plate by approximately 24%.
Overall, the 309L stainless steel cladding was effective in the corrosion resistance of the A36-A36 welded plate because no pitting and intergranular were noticed in the A36 areas. Moreover, the addition of the cladding layer could help slow down weight loss corrosion.
Coatings 2020, 10, x FOR PEER REVIEW 13 of 19 Figure 15 shows the weight-loss corrosion test results observed at the base material (A36) and the cladding material (309L and A36). The observed corrosions seemed to be uniform for both sites (W1 and W2). The calculated weight losses for the A36 plate was 14.51, and 11.11 mg/mm 2 for the cladding layer. The cladding layer could reduce the corrosion weight loss on the A36 plate by approximately 24%.
Overall, the 309L stainless steel cladding was effective in the corrosion resistance of the A36-A36 welded plate because no pitting and intergranular were noticed in the A36 areas. Moreover, the addition of the cladding layer could help slow down weight loss corrosion.

Wear Testing Results
The wear performance of the cladding surface could be observed in Figure 16. This figure compares the weight loss at varying shot blasting time between the substrate and the cladding. Increasing shot blasting time led to the increased weight loss of both surfaces since the top surface layers were eroded over time.

Wear Testing Results
The wear performance of the cladding surface could be observed in Figure 16. This figure compares the weight loss at varying shot blasting time between the substrate and the cladding. Increasing shot blasting time led to the increased weight loss of both surfaces since the top surface layers were eroded over time.

Wear Testing Results
The wear performance of the cladding surface could be observed in Figure 16. This figure compares the weight loss at varying shot blasting time between the substrate and the cladding. Increasing shot blasting time led to the increased weight loss of both surfaces since the top surface layers were eroded over time. It could be noticed that the weight loss of the cladding surface was lower than that of the substrate over time. Since the density of A36 steel was 7.85 g/mm 3 and the density of 309L stainless steel was 7.97 g/mm 3 , the calculated volume losses of the substrate and cladding were 0.248 and 0.226 mm 3 /h, respectively. The 309L stainless steel cladding surface reduced the volume loss by It could be noticed that the weight loss of the cladding surface was lower than that of the substrate over time. Since the density of A36 steel was 7.85 g/mm 3 and the density of 309L stainless steel was 7.97 g/mm 3 , the calculated volume losses of the substrate and cladding were 0.248 and 0.226 mm 3 /h, respectively. The 309L stainless steel cladding surface reduced the volume loss by approximately 9%, which could provide improved surface protection and a longer lifetime to the A36-A36 welded steel, particularly in the erosion environment. Figure 17 shows the top and cross-section views of the shot blasted surfaces. The surface roughness values of these surfaces were measured in Figures 18 and 19. The less abrasive surface could be found on the 309L stainless steel cladding (Ra = 1.92 µm) than on the A36-A36 substrate (Ra = 4.08 µm), which corresponded to the 9% less volume loss. approximately 9%, which could provide improved surface protection and a longer lifetime to the A36-A36 welded steel, particularly in the erosion environment. Figure 17 shows the top and cross-section views of the shot blasted surfaces. The surface roughness values of these surfaces were measured in Figures 18 and 19. The less abrasive surface could be found on the 309L stainless steel cladding (Ra = 1.92 μm) than on the A36-A36 substrate (Ra = 4.08 μm), which corresponded to the 9% less volume loss.

Discussion
Based on the results, the cladding of 309L stainless steel on the A36-A36 welded steel plate offered higher tensile strength at elevated temperature, corrosion resistance, and wear performance compared to the cases with no cladding (A36-A36 only). Since the primary purpose of the cladding was only to extend the lifetime of the welded components temporarily, the evaluations carried out in this work indicated that the coating method was proven effective. The cladding layer of 309L stainless steel provided an approximately 16% increase in the tensile strength at 500 °C and offered a suitable

Discussion
Based on the results, the cladding of 309L stainless steel on the A36-A36 welded steel plate offered higher tensile strength at elevated temperature, corrosion resistance, and wear performance compared to the cases with no cladding (A36-A36 only). Since the primary purpose of the cladding was only to extend the lifetime of the welded components temporarily, the evaluations carried out in this work indicated that the coating method was proven effective. The cladding layer of 309L stainless steel provided an approximately 16% increase in the tensile strength at 500 • C and offered a suitable protection layer to prevent any pitting and intergranular corrosions. The results obtained from this study agree with other existing studies suggesting that stainless steel weld cladding could be coated on a steel surface to prevent corrosion [55]. The findings from this study also confirmed that the 309L stainless cladding could be temporarily coated onto the A36-A36 welded components, particularly for the elevated temperature under such corrosive environments. This work's implication was the significant cost-saving by simply cladding the welded pipes with 309L stainless steel.
The next step following this work would be looking at the appropriate ratios between the welded steel and cladding material. Thus, the chemical analysis would be necessary. Besides, the shear tests would be examined to evaluate the shear strengths of these coated materials. The creep performances of the coated materials must also be performed to determine if the cladding surfaces could be operated under the thermal-fatigue conditions. Our research group also planned to develop a buffer layer to increase the oval performance and extend the coated materials' lifetime. The immediate implication of these studies was to apply the same coating technique in dissimilar welds, which were also commonly used in power plants.

Conclusions
This study evaluated the mechanical properties of the 309L stainless steel cladding on the A36-A36 welded plate. The welded samples were prepared by the GTAW and SMAW processes, and the cladding layer was coated onto the welded plate by SMAW. The residual stress measurements were carried out to observe the stress distributions after welding. The tensile strengths of the cladding samples at various layers were also investigated by using the tensile tests. Different sites of the cladding samples were also observed under the pitting, intergranular, and weight loss corrosive conditions. Finally, the shot blasting tests were conducted to determine the wear resistance performance of the coated surfaces. The key findings of this study were as follows: • The high compressive stress locations were mainly found in the Weld Metal and HAZ zones in the center area of the cladding surface. However, the overall stress distribution was considered typical and would not lead to lower fatigue resistance.

•
The increased tensile strength of 16% at 500 • C could be obtained by cladding 309L stainless steel on the A36-A36 welded plate.

•
No pitting and intergranular corrosions could be observed on A36 base material if coated with 309L stainless steel cladding. Also, the cladding layer improved weight loss corrosion by 24%.

•
The 309L stainless steel cladding provided less volume loss of 9% compared to that of the A36-A36 welded plate with no coating under the shot blasting wear tests.
The obtained results indicated that the 309L stainless steel cladding could be used to temporarily extend the lifetime of A36-A36 welded components in elevated temperature under corrosive and erosive conditions.