Superalloys
guaranteed heat- and corrosion-resistant
Wherever the requirements for materials increase and where high operating temperatures prevail, that is where the so-called superalloys or HRSA (heat-resistant super alloys) come into play. These are alloys with a complex composition. They are appealing because of their property to retain their stability and hardness even at high temperatures and to be corrosion-resistant.
The characteristics
Super alloys are divided into three main groups:
Fe-based alloys are an advancement of austenitic stainless steels and of all super alloys have the lowest heat resistance. They are suitable for the manufacture of housings, shafts and rings. For example, Incoloy 909, A286, Greek Ascoloy.
Ni-based alloys form the most frequent group among the super alloys. They are being used more and more in aircraft construction, for combustion chambers and turbine housing of jet engines or in gas turbine construction. For example, Inconel 718, Inconel 625, Waspaloy, Hastelloy.
Co-based alloys are characterized by extremely good corrosion resistance even at high temperatures. These materials are costly and difficult to machine. Use today is limited to applications in a hot or very corrosive environment (nuclear reactors, medical implants). For example, CoCr, Haynes 25, Stellite 31 (see special chapter CrCo alloys).
- Example of material: Inconel 625
- Corrosion protection: very high
- Acid resistance: very high
- Heat resistance: high to very high
- High degree of hardness even at high temperatures
- Not heat-treatable (low C content ˂ 0.07%)
- Not magnetic
- Thermal conductivity: low
- Hot and cold formability: very good
- Coefficient of thermal expansion: high
- Retention of stability and hardness even at high temperatures
- Mechanical properties: very good (high tensile strength, elongation at break)
- Toughness: high even at low temperatures
- Machinability: very challenging
- Main application areas: chemical industry, aviation, power generation, medical technology
- Cost of materials: very high
The Challenge
The extremely high degree of hardness and the low thermal conductivity generate high temperatures during machining. The tendency towards strain hardening and surface hardening increase wear on the tool's cutting edges. These properties of the material make these heavy-duty alloys a challenge for the operator. Add to this a pronounced toughness which constitutes an additional hurdle when it comes to chip formation and removal.
For this reason, alternative wear-free methods (electric discharge machining or laser) are often preferred especially when drilling. However, these reach their limits in the aerospace industry where there are strict regulations with respect to peripheral area quality. Machining with cutting tools has a clear advantage in this respect but overheating of tools, bonding of chips and material buildup on cutting edges have to be overcome.
The solution
It is possible to machine these heat-resistant superalloys reliably using cutting tools (such as carbide drill bits). In the search for suitable solutions Mikron Tool has considered these special properties and included them in the tool development.
Cooling system
Cooling was treated like a key issue just like in all heat and corrosion-resistant materials. Whenever possible, tools from Mikron Tool (drill bits and milling bits) have internal cooling integrated in the shaft as cooling channels for small dimensions and arriving up to the drill tip for larger dimensions.
Tungsten carbide
The carbides used by Mikron Tool for the machining of superalloys are resistant to thermal shock and simultaneously possess a high degree of bending strength and fracture toughness.
Geometry
The geometry is so designed that no high cutting forces are needed despite the extreme toughness of the material, the tool possesses a high degree of stability and the cutting edges guarantee good chip break with simultaneously good chip removal from the machining area.
Coating
The coating is temperature and oxidation-resistant with high wear resistance and low adhesion to metals.
Machining Process
Challenging materials such as superalloys, apart from a suitable tool, also require a clearly defined machining process. 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 good chip flow.
The Application Domains
- Chemical industry (valves and pumps, chemical reactors)
- Aviation (e.g. engines, turbines, fastening components)
- Medical technology (implants)
- Automotive industry (e.g. valve equipment, catalytic converters)
- Power generation (e.g. pwer plant generators)
- Electronics (electronic hardware, computer hardware)
Sample applications
Aerospace industry
- With CrazyDrill SST-Inox and CrazyDrill Crosspilot
Ball joint (e.g. slanted drilling diameter 1.6 mm (.063”) /drilling depth 12.5 mm (.492”) in Alloy 201 with 99.2% nickel content. Preceding inclined pilot drilling with CrazyDrill Crosspilot)
- With CrazyDrill Twicenter
Engine part, hole for oil flow (e.g. centering a hole with diameter 1.9 mm (.0748”) in Hastelloy X)
- With CrazyDrill SST-Inox
Engine part, hole for oil flow (e.g. hole diameter 1.9 mm (.0748”) /drilling depth 15 mm (.591”) in Hastelloy X)
Energy
Gas Turbine (for example pilot drilling and drilling Ø 4 mm (.157“) / drilling depth 10 x d, in Inconel 625, 2.4856)
Automotive
- With CrazyDrill Twicenter
Needle seat (e.g. centering a hole with diameter 1.7 mm (.0669”) in Inconel 625, NiCr22Mo9Nd, 2.4856. Follow-up drilling with CrazyDrill Cool)
- With CrazyMill Cool
Cylinder head, racing component (milling of pockets diameter 5 mm (.197”) depth 1 mm (.0393”) and diameter 7 mm (.276”) / depth 1 mm (.0393”) in HRSA Inconel 718, 2.4668)
The Products
Mikron Tool offers a series of standardized products for the machining of superalloys, especially nickel-based superalloys. The given cutting values correspond to results obtained during practical tests. There are also many possibilities of customer-specific tools such as solid carbide 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”), center tool with through-tool cooling
- Pilot / short drilling in the diameter range from 0.2 mm to 2 mm (.008” 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 6.35 mm (.039“ to .25“), drilling depth 3 x d, drill with through-tool cooling, with 90° chamfer
- Drilling in the diameter range from 0.2 mm to 2 mm (.008” to .0787”), drilling depth up to 12 x d, drill with or without through-tool cooling
- Drilling in the diameter range from 1 to 6.35 mm (.039“ to .25“), drilling depth up to 40 x d, drill with through-tool cooling
- Micro deep hole drilling in the diameter range from 0.2 to 1.2 mm (.008“ 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 8 mm (.0118” to .315”), milling tool with through-tool cooling
CrazyMill Cool Square & Corner radius
- 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 8 mm (.039” - .315”), 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 superalloys depending on the application. Contact us here to know more about these possibilities.