Effect of hybrid thermomechanical treatment on surface properties of steel

• Main Author: Chandrakumaran, Surendra
• Other Authors: Zhou Wei
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Aeronautical engineering
• Online Access: https://hdl.handle.net/10356/158109
• Institution: Nanyang Technological University

Hammer peening and laser heating have been found to be highly effective as surface enhancement methods on metals due to their ability to alter both the mechanical properties and the tribological properties of metals. As technology is constantly improving, there is a need to identify how the inclusion of two separate processes that have been used for years can have a significant impact when done together. By doing so, we can create and further test more hybrid processes that can be beneficial for use in the future. In this study, Grade 431 Martensitic Stainless steel had undergone both robotic hammer peening and laser heating. As such, the author had to prepare the samples for metallurgic testing and examine them via hardness testing, microscopes, surface roughness testing and compressive residual hardness testing to analyse the different characteristic that were present through the different profiles of the specimen where different processes were conducted on. This project was done to study the effects that each individual process has on the material along with studying the effects that the combination of both processes has on the material. It also showcases how different process parameters may affect the overall result between similar processes. In-depth analysis was carried out to establish relation between the tests carried out and their effect on the hardness profile, surface roughness, wear, and residual stress of the material. Experimental results from the various testing methods used show that the combination of both processes would enhance the material properties of the metal as compared to when both processes are done separately. When only laser heating is done it would produce samples with higher depth of hardness of up to 0.2mm below the surface the surface of the specimen. When only hammer peening is done it would produce samples with the higher overall compressive residual stress depth of up to 0.8mm below the surface of the specimen when these processes iv are compared with the samples that have undergone both processes that have a hardness depth of up to and a compressive residual stress depth of up to 0.3mm below the surface of the specimen. It can also be seen that the speed through which the processes are done has a significant impact on improving the material properties as the processes that are done at a faster speed tend to have more favourable results as compared to the processes that are done at a slower speed. For future works, the author would recommend reversing the method through which the processes would be done with hammer peening being done first followed by laser heating and to also make use of other testing methods for further in-depth analysis of how the processes would affect the materials properties both individually and together.