Stainless steel is a metal material widely used in many industries because of its high tensile strength, toughness, and corrosion resistance. Machining stainless steel is challenging due to its high work hardening tendency, low thermal conductivity, and ductility of the material resulting in built-up edge formation. Machining stainless steel at lower cutting speeds must be performed with coolant, which adds to the cost of the process and increases concerns for the environment and the operator's health and safety. Industries such as the aerospace and die-mold industries demand high-speed machining to realize productivity targets. Therefore, a cermet tool material was selected for the present study because of its high temperature resistance, high bending strength, and fracture toughness.
The study focused on investigating wear mechanisms and developing a coating on a cermet tool for dry high-speed machining stainless steel to increase tool life. The wear mechanisms of tools were investigated at a fixed cutting interval in relation to the tool's composition and microstructure. Scanning Electron Microscope (SEM) was used to study the microstructure and identify elements on the tool. X-ray diffraction (XRD) was used to identify the phases and concentrations of key elements on the tool. The new advanced in-house coating was developed with Super Fine Cathode (SFC) technology on a Kobelco AIP-20 Physical Vapour Deposition (PVD) coater. The micromechanical properties of the commercial coating and in-house coatings were investigated with the help of nanoindentation and scratch tests. Atomic Force Microscopy (AFM) and SEM were used to investigate the coating microstructure and surface topography. An Alicona variable focus 3D microscope was used to investigate wear volume and wear behaviour.
It was discovered that various secondary carbides used by manufacturers to manufacture cermet tools change the microstructure, which affects the machining performance of the cermet tool material. Microchipping at the depth of cut (DOC) causes catastrophic notch wear. It was found that the developed in-house coatings were able to delay the initial wear (microchipping), which improved the tool's life by 318%. This research contributes to meeting the manufacturing industry's challenging demand for dry-high speed machining with reduced manufacturing costs. / Thesis / Doctor of Philosophy (PhD) / Cutting is the process of removing unwanted material from the bulk material to obtain the desired shape. Each metal material has unique mechanical properties that lead to various machining challenges. The cutting process is done with the help of a cutting tool that wears out during the process, and a coating layer is often used to protect the tool. Stainless steel 304 is a widely used material that is difficult to machine. This study includes a systematic approach to understanding the wear mechanisms of tools and existing commercial coatings during the dry machining of stainless steel 304. An in-house coating was developed and deposited on the selected cutting tool to protect it, reduce tool wear and extend its working life. The research results will help reduce machining costs by reducing tool and coolant costs and meet the current industry demand for dry high-speed machining. It will also reduce environmental impact by reducing waste and hazardous chemicals and addressing occupational health and safety concerns.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/26982 |
| Date | January 2021 |
| Creators | Patel, Uttkarsh Sandeepbhai |
| Contributors | Veldhuis, Stephen, Mechanical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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