Research on Wear Life of High Speed Cutting Tools
Since the 1980s, due to breakthroughs in the design and manufacture of functional components such as the spindles and feed systems of numerically-controlled machine tools, the spindle speed and feed rate of CNC machine tools have been greatly improved. Under the impetus of all-round advancements in modern manufacturing technology, cutting has been promoted. Processing technology has entered a new phase of high-speed cutting. At present, high-speed cutting has been applied in a large number of manufacturing fields such as molds, aerospace, and automobiles, resulting in significant economic benefits, and is expanding into other application areas.
High-speed machining imposes a series of new requirements on tools. Studies have shown that high-speed cutting, the main cause of tool damage is due to cutting force and cutting temperature due to mechanical / machine / friction, bonding, chemical wear, chipping, broken and plastic deformation caused by wear and tear. Therefore, the main performance requirements for high-speed cutting tool materials are heat resistance, wear resistance, chemical stability, thermal shock resistance, and crack resistance of the coating. Tool materials such as ceramics, CBN, PCD, and cermets have good heat resistance and wear resistance. When their toughness is improved, they are very suitable for high-speed cutting. The development of advanced coating technology has further improved the performance of tool materials. At present, the development of new coating materials and coating processes is in the ascendant, indicating that the coated cutting tools will have great potential for development and broad application prospects in the field of high-speed cutting.
This article gives a comprehensive review of the wear mechanisms of ceramic tools, cubic boron nitride tools, diamond tools, cermet tools, and coated tools during high-speed machining. The wear patterns and wear life of the tools are analyzed. These studies will benefit Reasonable selection and wear control of high-speed cutting tools in actual production and processing.
Wear patterns of high-speed cutting tools
During high-speed cutting, the main wear patterns of the tool are flank wear, micro chipping, boundary wear, exfoliation, crater crater wear, and plastic deformation.
Back flank wear is the most common form of wear for high-speed cutting tools and can be considered as normal tool wear. The increase of the wear width of the flank will cause the tool to lose the cutting performance. In the high-speed cutting, the width of the uniform wear zone VB is often used as the wear limit of the tool.
Micro chipping is a small gap generated in the tool cutting edge, often occurs in intermittent high-speed cutting, through the use of a good tool material toughness, reduce the amount of feed, change the tool angle to increase stability, etc. Can reduce the probability of occurrence of micro-disintegration. Usually, as long as the tool's micro chipping is controlled within the wear limit, the tool can continue cutting.
Boundary wear occurs at the blade-work contact edge of the flank face of the tool. The shape is usually a narrow groove and is therefore also referred to as groove wear. In high-speed cutting of stainless steels and high-temperature alloys (such as Inconel 718), the tool is subject to boundary wear. The reason is that work hardening of the workpiece surface makes the hardness of the workpiece material at the blade-work contact boundary the highest. When processing the outer circle, the cutting speed of the blade-work contact boundary is the highest, and therefore the boundary wear is also easily formed. In addition, the boundary wear is also likely to occur when high speed cutting of cast iron is performed with a ceramic tool.
Flake spalling occurs on the front and back surfaces of the tool, which is caused by the contact fatigue or thermal stress fatigue of the knife-chip or blade-work contact area. When spalling is very small, it is considered to be wear; but in many cases, due to the fact that the source of fatigue cracks has a certain depth from the tool surface, the spalling block formed after crack propagation is often larger than the wear limit of the tool. Once the spalling occurs, the tool can be made. Failure, the formation of peeling damage. In the case of milling of steel and cast iron at the end of ceramic cutting tools, shell-like peeling often occurs on the rake face; the coated cutter is prone to flaking due to insufficient bonding strength between the coating material and the base material.
The wear of crater craters is most often seen in the high-speed machining of plastic metals. Plastic deformation mostly occurs under cutting conditions where the cutting temperature is high and the tool is hard-red. Superhard tool materials may also undergo plastic deformation at high cutting speeds.