To reiterate, so we know what our objective was: to achieve successful deposition of Stainless Steel 304L on the same material and a 3-axis mill, namely the HAAS Model TM-1 “Tool Room Mill” was used for this purpose.
Process Overview:
Figure 1 shows an overview of the steps we took to complete this project.
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| Figure 1: Steps undertaken |
We ran a total of 47 tests during the two rounds of experiments. Parameters varied were the spindle speed and traverse feed. Tests were performed for all the parameters using Al and SS backing plates. Each test took approximately 1 minute to perform and involved an average of 20 minutes of waiting time for the test pieces to cool down.
Below is a video of an ideal deposition condition:
Key Findings:
We used the Alicona Infinite Focus to generate 3D images of the top surface and cross sections of the deposition. For now, the images are used only for visualization, but they could be used in the future for further analysis, such as measurement of surface roughness, waviness etc.
Figure 2 shows the cross sections of depositions on two test pieces.
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| (a) | (b) |
| Figure 2: Cross section of (a) Satisfactory deposition (b) Unsatisfactory deposition | |
Figure 2(a) shows a satisfactory deposition of the consumable rod on the base plate. Figure 2(b) is an unsatisfactory deposition. A crack (circled in red) can be seen between the deposited layer and the base plate. Despite the fact that the deposited layer in 2(b) is thicker than in 2 (a), it would not be useful for the applications intended for this process.
Conclusions:
- A process window was established wherein successful depositions of SS304L can be made on the same material.
- The backing plate used significantly affects the quality of deposition due to a change in the rate of heat dissipation and deflection of the base plate. For the same parameters, SS backing plates resulted in better depositions than Al backing plates.
- Higher RPMs resulted in better, albeit thinner layered depositions.
Future work:
- Microstructure analysis of cut sections of the depositions and workpieces.
- Depositions of the best condition over an area that has through-holes drilled into it / cracks in the surface.
- Further tests with improved process parameters.
- Multi-layer deposition tests with similar process parameters.
References:
- Gandra, J., D. Pereira, R. M. Miranda and P. Vilaça. “Influence of process parameters in the friction surfacing.” Forty Sixth CIRP Conference on Manufacturing Systems 2013.
- Amit Kumar Singh, Madhusudan Reddy G, Srinivas Rao K. “Pitting corrosion resistance and bond strength of stainless steel overlay by friction surfacing on high strength low alloy steel.” Defense Technol 2015; 11:99-307.