Aspects And 2.2 Interpretation Of Regression Model

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5.2.2.2 Interpretation of Regression Model
The above equation can be written as
D ∝ P^0.058/(V^(-0.117) 〖D_b〗^(-0.133) )

By observing the above equation we can say that the LAZ Depth is directly proportional to the Laser Power and inversely proportional to the Scan Velocity and Beam diameter. The observations of the model can be summarized as below: As Laser Power increases the LAZ Depth of workpiece surface will also increase. This is because the heat input to the workpiece is increasing due to increase in Energy Density. As the Scan Velocity decreases the temperature on workpiece surface will increase. This is because with the decrease in Scan Velocity, the Power Density increases, those results in more heat input. As the Beam diameter decreases the area of contact get decreases, which result in more heat input. Due to this, as Beam diameter decreases the temperature on workpiece surface will get increases.

5.3 Characterization of hardened gray cast iron
5.3.1 Microstructure of untransformed zone
The microstructure of untransformed base material of cast iron as shown in figure 5.3 In order to check the degree of success of the laser surface hardening the microstructure is compared with pattern of the hardened material. The non-treated
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The pin holder was loaded by a load of 3, 5 and7 kg and the rotation speed of the disk was set to a value 344 rpm which corresponds to the sliding speed of 0.811m/s. The number of rotations was fixed to reach the sliding distance of 12000 m. Both contact surfaces were polished before the test with a polish paper. The samples used were made of gray cast iron substrates that were about 7 mm thick; they were created in a base material, 3 microchanels and 5 microchanels of layer pass. These pins are mounted in a pin holder in such a way that the both pin and disc surfaces mach to each other. Table 5.4 shows data used for wear

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