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Chromium-cobalt alloys represent a special group among the superalloys. Due to their high price and poor machinability they are only used when there are no other more cost-effective alternatives. Today these alloys are found predominantly in the medical technology because of their corrosion resistance and bio-compatibility. They are also especially suitable for dental equipment where in the mouth's humid environment a property such as "completely corrosion-resistant" is indispensable. Furthermore, since the price for the raw material is high, reliability constitutes an important factor in the decision as to how and with what tools a part is to be machined.
CoCr alloys are characterized by extreme hardness and simultaneously by high elasticity (double in comparison to precious metals). They are corrosion-resistant and acid-resistant even at high temperatures.
- Example of material: L605
- Corrosion protection: very high
- Acid resistance: very high
- Heat resistance: very high
- High degree of hardness even at high temperatures
- Not magnetic
- Thermal conductivity: low
- Hot and cold formability: very good
- Coefficient of thermal expansion: high
- Mechanical properties: good (high tensile strength, elongation at break)
- Toughness: high even at low temperatures
- Machinability: very challenging
- Main application areas: dental equipment, chemical industry, aerospace, medical technology
- Cost of materials: very high
The extremely high degree of hardness combined with high elasticity and poor thermal conductivity poses the highest demands on the machining process and tools are exposed to high wear. The surface tends towards strain hardening. With the price for the raw material being high, the process reliability is an important factor in the decision, how and with which tools a part is being machined.
Just like with iron-based or nickel-based alloys, Mikron Tool developers have also paid special attention to the characteristics of CrCo alloys. In particular, this means preventing the occurrence of excessive heat as much as possible either through proper cooling or by reducing the cutting forces.
The cooling is the key issue here, even more so than in other heat-resistant and corrosion-resistant materials. Whenever possible, tools from Mikron Tool (drills and milling cutters) have internal cooling which is integrated in the shaft as cooling channels at small dimensions and in larger dimensions twisting up through the tool to the drill tip.
The carbides used by Mikron Tool for the machining of chromium-cobalt alloys are resistant to thermal shock and simultaneously possess a high degree of bending strength and fracture toughness.
Because of a specially designed geometry and despite the high degree of toughness of the material, no high cutting forces are needed. The tool has a high degree of stability and the cutting edges guarantee a good chip break as well as a good chip removal from the machining area.
The coating is temperature and oxidation-resistant with high wear resistance and low adhesion to metals.
Who wishes to machine materials such as chromium-cobalt alloys also needs a clearly defined machining process for successful machining in addition to a suitable tool. The recommended cutting values and procedures in Mikron Tool products correspond to the results that were worked out during practical tests. Tool specialists took care to find the best possible combination of high cutting speeds and feed rates, proper cooling of cutting edges and simultaneously efficient chip flow.
The Application Domains
- Energy equipment: turbines, nuclear reactors components
- Dental equipment: tooth implants
- Medical technology: hip implants
- Aerospace industry: jet engine parts
- With CrazyMill Cool
Tooth crown (e.g. milling for pin, diameter 3 mm (.118”) in CrCo alloys)
- With CrazyDrill Crosspilot (custom-made product), customized stepped reamer and CrazyMill Radius Chamfer
Complete tooth crown (e.g. produce milled face with CrazyDrill Crosspilot, drill different diameters and ream with the hybrid tool "stepped hole reamer" diameter 1.95 mm – 2.7 mm (.0768” - .1063”), ream shape with customer-specific stepped reamer diameter 1.95 mm – 2.7 mm (.0768” - .1063”), evacuate material with insertion tool, deburr and chamfer complex edges with CrazyMill radius chamfer mill diameter 1.2 mm (.0472”)
Engine part (e.g. deep hole diameter 2.3 mm (.0906”) / drilling depth 20 x d in chromium-cobalt-alloy, L-605®)
Mikron Tool offers different standardized products in the small diameter range which are suitable for the machining of CrCo alloys. The cutting data indicated in the tables (see cutting data charts of the individual products) was proven in practical tests.There are also many possibilities of custom cutting tools such as smallest drill bits, step drills, milling bits, reamers, deburring tools, turning tools, form tools and combined tools.
- Centering in the diameter range from 0.3 mm to 6 mm (.0118” to .236”), centering tool with through-tool cooling
- Pilot / short drilling in the diameter range from 0.3 mm to 2 mm (.0118” to .0787”), drilling depth 3 x d, drill with through-tool cooling, with 90° chamfer
- Pilot / short drilling in the diameter range from 1 to 6 mm (.039“ to .236“), drilling depth 3 x d, drill with through-tool cooling, with 90° chamfer
- Drilling in the diameter range from 0.3 mm to 2 mm (.0118” to .0787”), drilling depth up to 12 x d, drill with and without through-tool cooling
- Drilling in the diameter range from 1 to 6 mm (.039“ to .236“), drilling depth up to 40 x d, drill with through-tool cooling
- Micro deep hole drilling in the diameter range from 0.3 to 1.2 mm (.0118“ to .047“), drilling depth up to 50 x d, drill with through-tool cooling
- Groove, pocket and wall milling in the diameter range from 0.3 mm to 6 mm (.0118” to .236”), milling depth up to 5 x d, milling tool with through-tool cooling
- Copy and side milling in the diameter range from 0.3 mm to 8 mm (.0118” to .315”), milling depth up to 5 x d, milling tool with through-tool cooling
- Plunge directly with up to 1 x d vertically into material, plunge mill in the diameter range from 1 mm to 6 mm (.039” - .236”), milling depths up to 2.5 x d, milling tool with through-tool cooling
- Customer-specific tools in the diameter range from 0.1 mm to 32 mm (.0039” to 1.259”)
Other CrazyLine tools are also suitable for the machining of CrCo alloys depending on the application. Contact us here to know more about these possibilities.