Friction Performance of 3D Printed Stainless Steel Rotors

"Friction Performance of 3D Printed Stainless Steel Rotors Manisha Upreti, Sai Krishna Kancharla, Vishal Reddy Singireddy, and Peter Filip *Southern Illinois University Carbondale, Illinois **Brucker, San Jose, California Manufacturing/casting defects and the corroding nature of grey cast iron require the attention of researchers to search for a better alternative to the grey cast iron rotors. The increasing demand and market of electric, hybrid vehicles draw attention of scientists and car manufacturers to conduct more research to find suitable and sustainable braking material that can overcome the issues related to grey cast iron rotors brakes. A modern alternative for grey cast iron rotors may be 3D printed stainless steel rotors. Additive manufacturing and 3D printing technology have changed the face of the traditional manufacturing industry. The promising future of 3D printing technology has propelled the manufacturing industry into a new era of customized fabrication. Thus, choosing 3D printing technology which can automate the manufacturing of rotors could be a good alternative to address the manufacturing defects related to grey cast iron rotors. Also, with a paradigm shift with regenerative braking, there is a need for a lightweight, non-corroding brake that can replace regular cast iron rotors. This study focuses on comparison of 3D printed stainless steel and commercially available grey cast iron rotors. The friction testing was conducted using a scaled down ISO/SAE J2522 procedure on a benchtop friction tester (Brucker UMT) equipped with an environmental chamber controlling temperature. The relative humidity was kept at constant value of 50%. Scaled down samples were manufactured from commercially available NAO brake pads with diameter of 13 mm were rubbed against rotors with diameter of 90 mm. The friction and wear mechanisms were studied by analyzing the surfaces of tested pads and rotors using scanning electron microscopy in secondary and backscattered electron modes (SEM, Quanta FEG 450 by FEI). The vibration and oscillation generated during testing with both rotors were also recorded and studied. The results showed that a more stable and smoother (better) friction layer was formed on stainless steel rotors (Ra=1.2 ?m) compared to grey cast iron rotors (Ra=2.4 ?m). This was responsible for a very stable and high friction level detected in systems with 3D printed rotors (average ? ~ 0.44 ? 0.01), when compared to the cast iron samples (average ? ~ 0.24 ? 0.1). Surprisingly a lower thermal conductivity of 3D printed steel did not negatively influence friction performance and wear. Wear of pads was measured after completion of the entire procedure and was extremely low in both systems (3D steel rotors 0.12 g, cast iron 0.11 g). Wear was not measurable on either type of rotors, which was ascribed to combination of material removal from rotors and material transfer to rotors from pads. Oscilloscope results, however, showed a higher damping effect in the grey cast iron rotors compared to the 3D printed stainless steel materials. As the graphite content in the grey cast iron is relatively high and graphite is absent in the stainless steel, the cast iron better absorbs shock vibrations induced by friction. Despite this damping advantage of the cast iron, the noncorroding nature of stainless steel, which is absent in the cast iron also attracts the attention of researchers while selecting the material for brake rotors discs. A further study of friction performance of 3D printed stainless-steel rotors is recommended to better understand its suitability for its commercial applications. [1] Rohit Jogineedi, Vishal Reddy Singireddy, Sai Krishna Kancharla, Swapnil S. Salvi and Ankur Jain, Peter Filip (2021), Impact of Microstructure and Surface Treatment on Thermal Properties of Gray Cast Iron Brake Rotors, Southern Illinois University Carbondale [2] David S. McKavanagh (2018), Scaling and Friction in Automotive Brake Materials, Comparison of Friction Phenomena Detected in Brake Dynamometer SAE J2522 and Scaled Down Bench-Top Tests, Southern Illinois University Carbondale [3] Bingheng Lu, Dichen Li, Xiaoyong Tian (2015), Development Trends in Additive Manufacturing and 3D Printing, DOI 10.15302/J-ENG-2015012 [4] Jian-Yuan Lee, Jian An, Chee Kai Chua (2017), Fundamentals and applications of 3D printing for novel materials, http://dx.doi.org/10.1016/j.apmt.2017.02.004 "