Influence Of Mechanical Process On The Stress Corrosion Cracking Of 316L Stainless Steel For Implant Application
316L stainless steel (SS) is very synonym as a metal implant in medical application. This 316L grade is widely used at various implant divisions and makes it beneficial to the medical treatment of several injuries and diseases. However, their usage is slightly limited by the corrosion problems durin...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://eprints.utem.edu.my/id/eprint/23981/1/Influence%20Of%20Mechanical%20Process%20On%20The%20Stress%20Corrosion%20Cracking%20Of%20316L%20Stainless%20Steel%20For%20Implant%20Application.pdf http://eprints.utem.edu.my/id/eprint/23981/2/Influence%20Of%20Mechanical%20Process%20On%20The%20Stress%20Corrosion%20Cracking%20Of%20316L%20Stainless%20Steel%20For%20Implant%20Application.pdf |
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| Summary: | 316L stainless steel (SS) is very synonym as a metal implant in medical application. This 316L grade is widely used at various implant divisions and makes it beneficial to the medical treatment of several injuries and diseases. However, their usage is slightly limited by the corrosion problems during implantation in the body. In this study, experiments are aimed to evaluate the stress corrosion cracking (SCC) of 316L SS in the simulated body environment. The 2.0 mm thick of 316L SS test specimens was undergone two steps mechanical processes; rolling and bending. The specimens were cold-rolled to 10%, 30% and 50% reduction in thickness and bent up to the U-bend shape using special bending equipment. The processing properties like plastic strain and springback after both processes were measured. The mechanical properties and structural modifications of cold worked specimens were assessed using tensile, hardness, bending and metallurgical tests. The corrosion tests were done in phosphate buffered saline (PBS) solution at temperature and pH of 37 oC and 7.4. The XRD and EDS methods were used to identify the corrosion products. Whereas, the morphology of SCC failed specimens was observed under microscopic method. From the results, the occurence of SCC has been evaluated as follows. The 316L SS was strain hardened after two steps mechanical processes. The strain hardening effect was clearly seen from the resulted processing properties and structural modification. It was indicated by a higher plastic strain and springback. The structural modification from coarse to dislocated and dense grain structures also makes the steel harder and stronger. Then, the bending process produced transversal cracks in the outer U-bend surface. The crack, which formed at the existing grain boundaries, was identified as the initial stage of SCC. Consequently, the chloride ions penetrate the crack during the corrosion process and facilitate the crack growth. The crack was propagated along with the previous rolled marks, under transgranular mode. In this work, SCC was clearly found on the U-bend 316L SS with 10% reduction in thickness. However, the steel with higher thickness reduction produced a greater strain hardening which then prevented the occurrence of transversal cracks. From the finding, this work shows the mechanical process greatly influenced the SCC rather than the corrosion process. The steel must be strain hardened by two steps mechanical processes to initiate the SCC failure. |
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