Attrition wear on broach cutting tools
Identification: Sometimes called Adhesion wear, this pattern is found on very slow surface feet per minute operations (10 SFPM to 25 SFPM). It is characterized by a very rough surface on the land and face of the tool. Usually, a Built Up Edge (BUE) is observed. Chips will be thick and not curl. Severe streaking of the finished part will be apparent.
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Abrasive wear on broach cutting tools
Identification: Deep, multiple scratches or scores are observed on the land (flank) of the tool. The scoring may appear predominantly on front rows of cutting teeth or it may appear randomly anywhere on the broach tool. The scoring will not appear uniform in length and will be at different positions across the land of the tool.
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Diffusion wear on broach cutting tools
Identification: A smooth cutting edge with a dark burned appearance very close to the edge will characterize the diffusion wear on a broach. Cratering of the tool face will be visible. Often, whole rows of cutting teeth will be broken away removing all evidence
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Built Up Edge
Identification: This common problem is identified by work piece material sticking to the face of the tool. The BUE often leads to chipping of the tool cutting edges. Often it will be an irregular wear pattern and will generate poor surface micro-finish on the part. Remnants of a BUE may show on the finished part as a streak left behind when the tool is extracted.
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Chipping Wear
Identification: This common problem is identified by sharp ragged edges on the used insert. The wear patter is irregular along the edge of the tool. Often, chipping wear leads to a catastrophic failure early in the life of the tool which masks the failure mode. Surface finish is usually streaked and uneven.
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Flaking
Identification: Flaking appears to be a large chip in tool. There will be one or two large areas missing the tool face.
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Spalling
Identification: This wear pattern is difficult to observe as it occurs relatively early in the life of the tool. If left in place, the tool will eventually demonstrate failure modes such as Crater, Flaking, Flank or Fracture wear. If Spalling and Thermal Cracking are both observed, treat the condition as Thermal Shock first. Since Spalling occurs early, other wear patterns develop that mask and may mislead the observer.
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Fracture
Identification: Often the evidence is lost when the insert is shattered. It may be the result of over use or severe overload. If it occurs very late in the life of the tool, other wear patterns probably existed such as Chipping, Crater, Deformation or Flaking and the tool was overrun.
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Flank / Nose / Face Wear
Identification: This is the most common wear pattern. It is uniform over a localized area and accelerates with higher temperatures. It appears as a rough surface primarily on the flank of the tool and to a lesser extent on the face of the tool. There will be a slight burn mark at the trailing edge of the wear pattern. This type of wear pattern is the most favorable mode when it is uniform and progresses slowly. It is the most favorable wear pattern compared to the other types of wear described in this document.
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Notching Wear
Identification: Notching wear is a single groove formation that occurs simultaneously on the face and flank of the tool at the depth of cut. This notch will cause poor micro-finish on the part and may preceed a Fracture failure mode.
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Thermal Cracking (Shock)
Identification: This wear pattern is unique as shows up as hairline cracks that are perpendicular to the cutting edge. Many times the parallel cracks are uniformly distributed long the cutting edge. These edge chips will appear to be very uniform in depth and are in line with the direction of tool travel. This wear pattern may appear on coated inserts that have Spalling wear patterns.
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Crater Wear (Diffusion Wear)
Identification: On the tool face, crater wear appears as a shallow trough in localized areas. Crater wear will increase until it reaches the cutting edge causing chipping or fracture. Chipping or fracture is an advanced crater wear condition and often misleading. The ridge at the edge of the tool near the tool edge will not have any BUE
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Deformation Wear
Identification: Deformation wear is always accompanied by a bulge of tool material in the flank / land area. There will be evidence of thermal lines seen as discoloration. This severe deformation is quickly followed by fracture. Micro-finish on the part may be very acceptable, while maintaining dimensional stability is difficult.
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Cobalt leaching wear
Identification: This tool wear pattern is often used to describe Notching, Thermal Cracking, and Crater (Diffusion). At low magnification, this wear pattern appears to be grooves in the cutting edge. However, at higher magnification, the grooves appear to be non-uniform and not linear which is unlike Thermal Cracking. Flank, Crater (Diffusion) and Notching wear patterns may logically be accelerated. Excessive cobalt leaching will turn the coolant red or pink.
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