**Table 2.**

**131**

**Figure 2.**

*Typical heat treatment cycle.*

*Analysis of Mechanical Properties of Austempered Ductile Iron Weld Joints Using Developed…*

*(a) Modified grove design, (b) schematic view of extracting samples from weld metal.*

Metallography samples of 20 × 10 × 15 mm dimensions were cut from the large size weld specimen and removed any decarburized skin by surface grinding. Samples were mounted at room temperature, then polished systematically in silicon carbide paper and followed by cloth polishing using 0.5 μm alumina solution. Polished samples were etched with 5% nital solution and microstructures are studied under an optical microscopy (Carl Zeiss made: AXIO Imager A1m) and photographs are taken at 500× magnification. For better clarity, samples were studied under scanning electron microscopy (SEM) (JEOL JSM-5510 with INKA software EDS system using an ultra-thin window detector) and photographs were taken at higher magnifications.

**Parameters Unit Value** Preheat temperature (1 h) °C 300 PWHT (1 h) °C 300 Welding current A 150 Arc voltage V 24 Welding speed mm/s 1.70 Heat input kJ/mm 1.58

*DOI: http://dx.doi.org/10.5772/intechopen.84763*

**Figure 1.**

**Table 3.**

*Defect free weld procedure.*

*Chemical composition of the weld deposits using developed coated.*

*Analysis of Mechanical Properties of Austempered Ductile Iron Weld Joints Using Developed… DOI: http://dx.doi.org/10.5772/intechopen.84763*

#### **Figure 1.**

*Recent Advancements in the Metallurgical Engineering and Electrodeposition*

**Element wt.%**

Trial 4 (without Ce)

Trial 7 (with Ce)

**Table 2.**

*Chemical composition of the weld deposits using developed coated.*

3.28

0.43

2.76

0.008

0.02

0.66

0.31

0.29

0.48

0.03

0.003

0.003

0.14

91.45

0.10

3.08

0.40

2.60

0.006

0.039

0.5

0.19

0.24

0.62

0.03

0.004

0.015

0.09

91.40

—

**C**

**Mn**

**Si**

**S**

**P**

**Ni**

**Mo**

**Cu**

**Al**

**Bi**

**Mg**

**Ca**

**Ti**

**Fe**

**Ce**

**130**

*(a) Modified grove design, (b) schematic view of extracting samples from weld metal.*


#### **Table 3.** *Defect free weld procedure.*

Metallography samples of 20 × 10 × 15 mm dimensions were cut from the large size weld specimen and removed any decarburized skin by surface grinding. Samples were mounted at room temperature, then polished systematically in silicon carbide paper and followed by cloth polishing using 0.5 μm alumina solution. Polished samples were etched with 5% nital solution and microstructures are studied under an optical microscopy (Carl Zeiss made: AXIO Imager A1m) and photographs are taken at 500× magnification. For better clarity, samples were studied under scanning electron microscopy (SEM) (JEOL JSM-5510 with INKA software EDS system using an ultra-thin window detector) and photographs were taken at higher magnifications.

**Figure 2.** *Typical heat treatment cycle.*

X-ray diffraction (XRD) analysis was performed to estimate the volume fraction of retained austenite and its carbon content using anode Co-Kα radiation in 1.79026 targets with 24 kV and tube current was 40 mA. The specified 2*θ* range was varied from 30 to 110° with a step size of 0.2°/min. Detailed XRD analysis was performed using integrated intensities of the positions and the integrated intensities for the {1 1 1}, {2 2 0} and {3 1 1} planes of FCC austenite as well as the {1 1 0} and {2 1 1} planes of BCC ferrite. The volume fraction of retained austenite was calculated using the following empirical formula [30]:

*<sup>X</sup>*<sup>γ</sup> <sup>=</sup> \_\_\_\_\_\_\_\_\_\_\_\_\_ *<sup>I</sup>*γ/*R*γ (*<sup>I</sup>*γ/*R*) <sup>+</sup> (*I*α/*R*α) (1)

Where *Iγ* and *Iα* are the integrated intensities and *Rγ* and *Rα* are the theoretical relative intensity for the austenite and ferrite, respectively, and Bainitic ferrite was calculated by using the formula:

$$X\_{\gamma} + X\_{a} + X\_{\mathfrak{g}} = \mathfrak{I} \tag{2}$$

Where, *Xγ* and *Xα* and *Xg* represent the volume percentage of retained austenite, volume percentage of bainitic ferrite and volume percentage of graphite. The carbon concentration of the austenite was determined using the equation [30].

$$a\_{\uparrow} = 0.3548 \star 0.0044 \,\mathrm{C\_{\uparrow}} \tag{3}$$

Where *aγ* is the lattice parameter of austenite (in nm) and *Cγ* is the carbon content of austenite (in wt.%). The {1 1 1}, {2 2 0} and {3 1 1} planes of austenite were used to estimate the lattice parameter.

Vickers microhardness test of the weld metals was performed at room temperature using Leco Vickers microhardness tester (Model LM 248SAT) with 100 gf load at 10 s holding. The hardness values were taken from six different positions of each weld specimens and the average of the six values considered the final one.

Tensile properties such as ultimate tensile strength (UTS), yield strength (YS) and % elongation of the welded joints were evaluated using transverse tensile specimen keeping the weld metal at the center of the gauge length. The tests were performed under uniaxial loading at a crosshead speed of 5 mm/min in universal tensile testing m/c (Instron 8862).

Sub-size (55 × 10 × 3.3 mm) and without notch transverse Charpy impact test of the ADI welded joints were performed at room temperature according to ASTM E-23 [31]. Four samples were tested at each austempering condition (300 and 350°C for the 2 h holding time) and an average of four values has been reported.

High cycle fatigue (HCF) test of transverse weld samples as per ASTM E466-15 [32] (**Figure 3**) were performed using Rumul resonant testing machine to determine

**133**

**Figure 4.**

*Analysis of Mechanical Properties of Austempered Ductile Iron Weld Joints Using Developed…*

mode and the number of cycles of failure was recorded with keeping the load ration R at 0.1. The stress levels were varied between 30 and 80% of Yield strength to obtaining the endurance limit and S-N curve was plotted by stress amplitude and the

After successfully testing, fracture surface and crack path of the tested samples were studied under SEM and fractographs were taken at different magnifications.

**Figure 4** shows the optical microstructure of as-cast DI (base metal). The microstructure shows graphite nodules surrounded with ferrite matrix. The average

The optical microstructures of weld metals using two selected coated electrodes

It has been shown that cerium reduces both primary [33] and secondary [34] dendritic arm spacing as well as inhibit the development of columnar crystal.

containing without and with Ce is shown in **Figure 5**. In **Figure 5a** and **b**, the microstructure shows ledeburitic carbide (LC), alloyed pearlite (AP) and graphite nodules (G). In both the weld metal microstructure shows small amount of graphite nodules with smaller in size due to higher cooling rate experienced in weld metal. Although both the as-weld microstructure shows similar microstructural appearance, a close look into the microstructure reveals difference in grain size and volume percentage of ledeburitic carbide and alloyed pearlite. The presence of Ce in weld metal has caused the structure finer (the finer the dendritic structure), lesser ledeburitic carbide, higher amount of alloyed pearlite and increasing the graphite

nodularity shows 90% with 130 nodules per unit area (mm<sup>2</sup>

cycles at constant stress control

) and average nodule

*DOI: http://dx.doi.org/10.5772/intechopen.84763*

number of cycles in log-log scale.

**3. Results and discussion**

*3.1.2 As-welded microstructure*

volume percentage and nodularity.

*Optical microstructure of as-cast ductile iron.*

**3.1 Microstructure**

*3.1.1 Base metal*

size is r = 18.5 μm.

the S-N curve. The tests were run to failure up to 107

**Figure 3.** *Schematic view of transverse high cycle fatigue sample as per ASTM 606.*

*Analysis of Mechanical Properties of Austempered Ductile Iron Weld Joints Using Developed… DOI: http://dx.doi.org/10.5772/intechopen.84763*

the S-N curve. The tests were run to failure up to 107 cycles at constant stress control mode and the number of cycles of failure was recorded with keeping the load ration R at 0.1. The stress levels were varied between 30 and 80% of Yield strength to obtaining the endurance limit and S-N curve was plotted by stress amplitude and the number of cycles in log-log scale.

After successfully testing, fracture surface and crack path of the tested samples were studied under SEM and fractographs were taken at different magnifications.
