For some background on the pictures in this Archive section see About Tool Failure page…
1. Attrition wear on low speed 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. Causes: Welding of the part material to the tool causes minute pieces of the tool material to be dislodged with the work piece or with the BUE. Cure:Click here to contact Machining Efficiencies.
2. Abrasive wear on low speed 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. Causes: The cutting edge is coming in contact with a very hard matrix related to the part metallurgy.These hard particles are harder than the tool itself. Cure:Click here to contact Machining Efficiencies.
3. Diffusion wear on low speed cutting tools(See Diffusion wear on Inserts) Identification:A smooth cutting edge with a dark burned appearance very close to the edge will characterize diffusion wear. Cratering of the tool face will be visible. Causes: The temperatures created in the cutting zone are too high for the the tool material allowing it to diffuse into the work piece or the chips.
4. Built Up Edge (BUE) 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. Cause: BUE is caused by low surface feet per minute or poor shearing action of the work piece material. The work piece material is adhering to the surface of the tool due possibly to improper insert geometry or an affinity of the work material to the insert or its coating.BUE is also caused by coolant issues such as improper physical application of the coolant, insufficient anti-weld characteristics, or tramp oil levels. Cure:Click here to contact Machining Efficiencies.
5. 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. Causes:Mechanical issues such as machine spindle or part fixture vibration will contribute to chipping wear.A tool holder with a large cantilever condition will cause harmonic vibrations to be amplified at the cutting edge.Excessive loads on the tool will cause chipping.
6. Flaking Identification: Flaking appears to be a large chip in tool.There will be one or two large areas missing the tool face. Causes: Flaking occurs on tools that are too brittle for the application, usually ceramic tools.It maybe caused by a sudden impact when the tool enters the work piece or if the tool is extracted during a heavy load.
7. Spalling Identification: This wear pattern is a characterized by a large shelf lost coating. Causes: In the early development of coatings, spalling was related to a delamination of the TiN or other coating.Today, Spalling is caused by several conditions such as excessive mechanical loading on tool due to high speed and feed.It can be caused by cobalt leaching. Cure:Click here to contact Machining Efficiencies.
8. Fracture Identification: This wear pattern is 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. Causes: Fracture wear is related to severe loads on the cutting tool such as hard spots in the work piece.Most of the time, this failure mode is caused by excessive speed or feed. Cure:Click here to contact Machining Efficiencies.
9. 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.It is the most favorable wear pattern compared to the other types of wear described in this document. Causes: High surface feet per minute operations will wear the tool where it drags on the finished surface. An incorrect insert substrate or coating will promote this wear pattern.Cobalt leaching may accelerate this wear pattern.
10. 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. Causes: Machining parts with severe (hard or oxidized) surfaces will cause notching wear.It is common in machining materials that contain nickel.Cobalt leaching may accelerate this wear pattern.
11. Thermal Cracking (Shock) Identification: This wear pattern is unique as shows up as hairline cracks that are perpendicular to the cutting edge.Causes: This is usually caused by fluctuating heating and cooling cycles.The next most common cause is fluctuation mechanical loads related to excessive feed rates.
12. 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. Causes:Crater wear patterns indicate that the tool material is diffusing into the chip.It is related to very high temperatures on the tool face. Cobalt leaching may accelerate this wear pattern.
13. Deformation Wear Identification: Deformation wear is always accompanied by a bulge of tool material in the flank / land area.This severe deformation is quickly followed by fracture. Causes: Deformation wear is caused by excessive temperatures in the insert due to high cutting forces, excessive speed, and excessive feed rate.
Identification: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. Causes: Cobalt leaching is a chemical reaction between the cobalt binder of the insert and amino alcohols or other amine based additives found in most water miscible machining and grinding fluids.
If you are experiencing a consistent wear pattern and would like some insight, send me an email. If your tool wear pattern isn't consistent with one of those above, let's talk about it.
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