HPA COBALT alloy 6B (Co-Cr-W) (UNS R30016)


Co 60, Cr 28, W 4.50, C 1.15, Si 1.1


High Performance Alloys stocks and produces this grade in the following forms: Bar, sheet, plate and forgings. Request quote on this grade. See our on-line catalog for sizes stocked

 

Overview

 

Wear Resistant (Co-Cr-W)
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, 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 resists heat and oxidation, retains high hardness even at red heat (then 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.


Applications

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, & many other Misc. wear surfaces.

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.

Wrought alloy 6B offers the ductility, fatigue resistance and toughness of a hot worked microstructure, with the heat corrosion and wear resistance of cobalt based alloy. High Performance Alloys, Inc. inventories bar, sheet, and plate. Bar is stocked from 3/8" through 6" diameter. Bar can be supplied in random lengths or cut to order. Sheet and plate are offered as whole plates, can be abrasive cut, or processed further using water jet services.


Also see Cobalt 6BH - better than Alloy 6K. More ductility that knife applications require.

Wear resistance data.

 

Chemistry

Chemical Requirements

Ni

Cr

Mo

Mn

C

Si

Fe

Max

3.0

32.00

1.50

2.0

1.40

2.0

3.0

Min

28.00

0.5

0.90

0.2


Tensile Data

Mechanical Property Requirements

Ultimate Tensile min.

Yield Strength (0.2% OS) min.

Elong. in 2 in.(50mm) min., %

R/A % min.

Hardness

Min

130 KSi

70 Ksi

5%

7%

Max

Min

896 Mpa

483 MPa

Max


Specifications

Form

Standard

Metal Type

UNS R30016

Bar

AMS 5894

Wire

Sheet

AMS 5894

Plate

AMS 5894

Fitting

 

Forging

 

Weld Wire

 

Weld Electrode

 


 

Machining

Nickel & cobalt base corrosion, temperature and wear-resistant alloys are classified as moderate to difficult when machining, however, it should be emphasized that these alloys can be machined using conventional production methods at satisfactory rates. During machining these alloys work harden rapidly, generate high heat during cutting, weld to the cutting tool surface and offer high resistance to metal removal because of their high shear strengths. The following are key points which should be considered during machining operations:

CAPACITY - Machine should be rigid and overpowered as much as possible.
RIGIDITY - Work piece and tool should be held rigid. Minimize tool overhang.
TOOL SHARPNESS - Make sure tools are sharp at all times. Change to sharpened tools at regular intervals rather than out of necessity. A 0.015 inch wear land is considered a dull tool.
TOOLS - Use positive rake angle tools for most machining operations. Negative rake angle tools can be considered for intermittent cuts and heavy stock removal. Carbide-tipped tools are suggested for most applications. High speed tools can be used, with lower production rates, and are often recommended for intermittent cuts.
POSITIVE CUTS - Use heavy, constant, feeds to maintain positive cutting action. If feed slows and the tool dwells in the cut, work hardening occurs, tool life deteriorates and close tolerances are impossible.
LUBRICATION - lubricants are desirable, soluble oils are recommended especially when using carbide tooling. Detailed machining parameters are presented Tables 16 and17. General plasma cutting recommendations are presented in Table 18.

 

Table 16
RECOMMENDED TOOL TYPES AND MACHINING CONDITIONS
Operations Carbide Tools
Roughing, with severe interruption Turning or Facing C-2 and C-3 grade: Negative rake square insert, 45 degree SCEA1, 1/32 in. nose radius. Tool holder: 5 degree neg. back rake, 5 degree neg. side rake. Speed: 30-50 sfm, 0.004-0.008 in. feed, 0.150 in depth of cut. Dry2, oil3, or water-base coolant4.
Normal roughing Turning or Facing C-2 or C-3 grade: Negative rate square insert, 45 degree SCEA, 1/32 in nose radius. Tool holder: 5 degree neg. back rake, 5 degree neg. side rake. Speed: 90 sfm depending on rigidity of set up, 0.010 in. feed, 0.150 in. depth of cut. Dry, oil, or water-base coolant.
Finishing Turning or Facing C-2 or C-3 grade: Positive rake square insert, if possible, 45 degree SCEA, 1/32 in. nose radius. Tool holder: 5 degree pos. back rake, 5 degree pos. side rake. Speed: 95-110 sfm, 0.005-0.007 in. feed, 0.040 in. depth of cut. Dry or water-base coolant.
Rough Boring C-2 or C-3 grade: If insert type boring bar, use standard positive rake tools with largest possible SCEA and 1/16 in. nose radius. If brazed tool bar, grind 0 degree back rake, 10 degree pos. side rake, 1/32 in. nose radius and largest possible SCEA. Speed: 70 sfm depending on the rigidity of setup, 0.005-0.008 in. feed, 1/8 in. depth of cut. Dry, oil or water-base coolant.
Finish Boring C-2 or C-3 grade: Use standard positive rake tools on insert type bars. Grind brazed tools as for finish turning and facing except back rake may be best at 0 degrees. Speed: 95-110 sfm, 0.002-0.004 in feed. Water-base coolant.
Notes:
1 SCEA - Side cutting edge angle or lead angle of the tool.

2 At any point where dry cutting is recommended, an air jet directed on the tool may provide substantial tool life increases. A water-base coolant mist may also be effective.

3 Oil coolant should be premium quality, sulfochlorinated oil with extreme pressure additives. A viscosity at 100 degrees F from 50 to 125 SSU.

4 Water-base coolant should be premium quality, sulfochlorinated water soluble oil or chemical emulsion with extreme pressure additives. Dilute with water to make 15:1 mix. Water-base coolant may cause chipping and rapid failure of carbide tools in interrupted cuts.

 

Table 17
RECOMMENDED TOOL TYPES AND MACHINING CONDITIONS
Operations Carbide Tools
Facing Milling Carbide not generally successful, C- grade may work. Use positive axial and radial rake, 45 degree corner angle, 10 degree relief angle. Speed: 50-60 sfm. Feed: 0.005-0.008 in. Oil or waterbase coolants will reduce thermal shock damage of carbide cutter teeth.
End Milling Not recommended , but C-2 grades may be successful on good setups. Use positive rake. Speed: 50-60 sfm. Feed: Same as high speed steel. Oil or water-base coolants will reduce thermal shock damage.
Drilling C-2 grade not recommended, but tipped drills may be successful on rigid setup if no great depth. The web must thinned to reduce thrust. Use 135 degree included angle on point. Gun drill can be used. Speed: 50 sfm. Oil or water-base coolant. Coolant-feed carbide tipped drills may be economical in some setups.
Reaming C-2 or C-3 grade: Tipped reamers recommended, solid carbide reamers require vary good setup. Tool geometry same as high speed steel. Speed: 50 sfm. Feed: Same as high speed steel.
Tapping Not recommended, machine threads, or roll-form them.
Electrical Discharge Machining The alloys can be easily cut using any conventional electrical discharge machining system (EDM) or wire (EDM).
Notes:
5 M-40 series High Speed Steels include M-41 , M-42, M-43, M-44, M-45 and M-46 at the time of writing. Others may be added and should be equally suitable.

6 Oil coolant should be a premium quality, sulfochlorinated oil with extreme pressure additives. A viscosity at 100 degree F from 50 to 125 SSU.

7 Water-base coolant should be premium quality, sulfochlorinated water soluble oil or chemical emulsion with extreme pressure additives. Dilute with water to make 15:1 mix.

 

Table 18
Plasma Arc Cutting
Our alloys can be cut using any conventional plasma arc cutting system. The best arc quality is achieved using a mixture of argon and hydrogen gases. Nitrogen gas can be substituted for hydrogen gases, but the cut quality will deteriorate slightly. Shop air or any oxygen bearing gases should be avoided when plasma cutting these alloys.

 

More Specific 6B Machining
Alloy 6B is generally machined with tungsten-carbide tooling, and will produce a finish of about 200-300 RMS. Carbide inserts are used with a 5-degree (0.9 rad.) negative tool holder and a 30-degree (0.52 rad.) or 45-degree (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-degree (0.79 rad.) cutting lead angle should be used. High speed taps are not recommended for Alloy 6B but threads can be produced by EDM techniques. For better surface finish, this alloy should be ground.

6B is ground to obtain close tolerances with excellent finish properties. Do not quench dry ground material, as may cause surface imperfections.