Stellite® 6B - HPA 6B - UNS R30016 - Wrought Alloy #6 - Cobalt 6B - CoCrW AlloyHome > All Alloys > HPA 6B
|Table of Contents
|Machining, Welding, & Processing
Cobalt 6B is a cobalt based chromium, tungsten alloy for wear environments where seizing, galling, and abrasion are present. 6B is resistant to seizing and galling and with its low coefficient of friction. The low friction allows sliding contact with other metals without damage by metal pick up in many cases. Seizing and galling can be minimized in applications without lubrication or where lubrication is impractical. Metal seizing is similar to one metal piece building heat against another and they become "welded" together. Galling is when these "weld" areas break off and form an abrasive debris which creates additional abrasion problems.
Alloy 6B has outstanding resistance to most types of wear. Its wear resistance is inherent and not the result of cold working, heat treating or any other method. This inherent property reduces the amount of heat treating and post machining.
6B has outstanding resistance to cavitation erosion. Steam turbine erosion shields from 6B have protected the blades of turbines for years of continuous service. 6B has good impact and thermal shock resistance and resists heat and oxidation. Cobalt 6B retains high hardness even at red heat (when cooled, recovers full original hardness) and has resistance to a variety of corrosive media. 6B is useful where both wear and corrosion resistance are needed. Link to alloy 6BH.
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Applications for alloy 6B include half sleeves and half bushings in screw conveyors, tile making machines, rock crushing rollers, and cement and steel mill equipment. Alloy 6B is well suited for valve parts, pump plungers shafting, and sleeves.
Wrought alloy 6B offers the ductility, fatigue resistance, and toughness of a hot worked microstructure with the heat corrosion and wear resistance of a cobalt based alloy. Some common applications are steam turbine erosion shields, chain saw guide bars, high temperature bearings, furnace fan blades, valve stems, food processing equipment, needle valves, centrifuge liners, hot extrusion dies, forming dies, nozzles, extruder screws, and many other miscellaneous wear surfaces.
- Hot Worked, Aged, Air Cooled
- Density 0.303 lb/in3
- Specific Heat (@ 72 °F) 0.101 Btu/lb-°F
Thermal Conductivity (32 to 212 °F)
103 Btu-in./sq. ft.-hr.-°F
Electrical Resistivity (68 °F)
546 Ohms/ cir mil ft
- Melting Range 2310 to 2470 °F
- Electrical Conductivity compared to Copper 1.90%
- Reflecting Power 57 - 70%
Mean Coefficient of Thermal Expansion
32-212°F 7.7 microinches/in.°F32-932°F 8.3 microinches/in.°F32-1472°F 9.1 microinches/in.°F32-1832°F 9.7 microinches/in.°F
The typical properties listed can usually be provided in rounds, sheet, strip, plate, & custom forgings. We have the equipment to produce small quantities in special sizes to meet our customers’ specific needs. The table below shows Stellite's minimum Mechanical Properties of Alloy 6B per AMS 5894. For most common forms and exceptions, check out the datasheet linked underneath the table.
|UTS ksi (MPa)
|YS ksi (MPa)
|Elong. in 2 in., %
|Reduced Area, %
UTS = Ultimate Tensile Strength, YS = Yield StrengthLink to Stellite's datasheet on alloy 6B
Note that the specifications listed are common for this alloy but are for reference only and may be specific to a certain form. The specifications listed are not comprehensive nor indicative of any edition, revision, or similar such as an amendment. Please, reach out to our sales department to request the Material Test Report (MTR) or to confirm your required specifications.
|AMS 5894, PWA 1196, BMS7-338
|AMS 5894, PWA 1196, BMS7-338
|AMS 5894, PWA 1196, BMS7-338
Alloy 6B can be welded by gas tungsten-arc (TIG) with an argon flow of 25 CFH, gas metal-arc (MIG), shielded metal-arc (coated electrode), and oxy-acetylene in this order of preference. The oxy-acetylene method should be used with discretion and care in that alloy 6B will “boil” during welding which may cause porosity. Use a 3X reduction flame to minimize oxidation, penetration, and inter-alloying.
Alloy 6B should be preheated and maintained at 1000ºF minimum to prevent cracking during welding and then still air cooled. Fixturing which would chill the weld rapidly should not be used. Standard weld joints are recommended. Alloy No. 25 filler metal is recommended for joining alloy 6B to softer materials such as carbon steel or stainless steel, while the harder cobalt base filler metals such as No. 6 and No. 21 are recommended for joining alloy 6B to itself, especially if wear resistance is required in the weld areas. In the latter case, No. 25 may be used for the root passes and then be overlayed with the harder materials. Gas shielding of the root side of the gas tungsten-arc weldments is not mandatory but it is recommended in order to improve weld penetration.
Alloy 6B is readily joined to other materials by brazing. All forms of surface dirt such as paint, ink, oil, chemical residues, etc., must be removed from the mating parts by etching, solvent scrubbing, degreasing, or other means. In addition, fluxing will be required during torch brazing operations when using silver brazing filler metal, to help clean the joint and allow the filler metal to flow more freely over the mating surfaces. Generously brush joining areas with brazing flux prior to heating. When torch or induction brazing, as soon as the brazing filler melts, the source of heat should be removed and the parts positioned. The assembly should then be pressed together to squeeze out the excess flux and still air-cooled. The parts should not be quenched.
Other brazing filler metals (i.e., gold, palladium, or nickel-base alloys) are satisfactory for joining alloy 6B. Brazing filler metal selection depends on the service conditions expected.
A close fit of the mating surfaces is recommended. The finished joints will have greater strength if the filler metal is very thin, generally 0.001- 0.005” thick.
Brazing, with high-temperature filler materials, is generally performed in a furnace. Induction and resistance heating with salt-bath and metal-bath dip brazing have limited application. Vacuum furnaces held at less than one micron pressure or controlled atmosphere furnaces, having adequate moisture control at brazing temperatures, produce the most satisfactory results. Controlled atmospheres such as hydrogen or cracked ammonia are suitable for brazing alloy 6B base materials.
Alloy 6BH is generally machined with tungsten carbide tooling, and will produce a finish of about 200-300 RMS. Carbide inserts are used with a 5° (0.9 rad.) negative tool holder and a 30° (0.52 rad.) or 45° (0.79 rad.) lead angle. Tools for facing or boring are essentially the same except for greater clearances where needed. For best results in drilling, the drill web should be kept thin. Screw machine length, carbide tipped drills should be used. In reaming, a 45° (0.79 rad.) cutting lead angle should be used. High speed taps are not recommended for Alloy 6BH but threads can be produced by EDM techniques. For better surface finish, this alloy should be ground.
6BH is ground to obtain close tolerances with excellent finish properties. Do not quench dry ground material as it may cause surface imperfections.Link to alloy 6BH.
ReferencesLink to Stellite's datasheet on alloy 6B
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Data referring to mechanical properties and chemical analyses are the result of tests performed on specimens obtained from specific locations of the products in accordance with prescribed sampling procedures; any warranty thereof is limited to the values obtained at such locations and by such procedures. There is no warranty with respect to values of the materials at other locations.