Machining of Nickel Alloys

Nickel alloys can be machined successfully, but this requires an understanding of how their properties and chemical composition affect machinability. Nickel alloys are characterized by high strength at elevated temperatures, and during machining the material heats up; however, steel and nickel alloys heat up at different rates because they have different thermal conductivity. Many precipitation-hardened nickel alloys also contain particles of titanium and aluminum, which have abrasive properties. The handbook ASM Specialty Handbook: Nickel, Cobalt, and Their Alloys classifies nickel alloys into five categories and provides machining parameters for various types of machining for each category. This article presents machining parameters for alloys in each of these categories.

Group A - very easily machineable nickel alloys

This category mainly includes commercially pure nickel used in caustic alkaline environments and in the chemical and electrical industries. These alloys have low strength and can only be slightly strengthened by cold working.

Sample alloys include:

Nikiel 200 / 2.4066 - commercially pure nickel. 

Alloy 205 - small Ti and Mg alloying additions.

Alloy 212 - used in electronics.

General guidelines - best to machine after cold word, as they can be quite gummy in the annealed condition.

Boring and turning nickel alloys with high-speed steel:

• roughing: speed 52 m/min; feed 0.2 mm/rev
• finishing: speed 61 m/min; feed 0.1 mm/rev

Twist drilling nickel alloys with high-speed steel:

• drill D <1.6 mm 
• speed 17-23 m/min
• feed 0.01-0.03 mm/rev

Tapping and threading nickel alloys with high-speed steel:

• tapping: feed 5-8 mm/rev
• threading: speed 7,6-9,1 m/min

Broaching nickel alloys with high-speed steel:

• speed 3.1-5,5 m/min
• angle 12-18°

Planing and shaping nickel alloys with high-speed steel:

• roughing: depth 16 mm; feed 0.13 mm; speed 15-18 m/min
• finishing: depth 0.25 mm; feed 6,35 mm; speed 15 m/min

Face and side milling with 1.3343 HSS:

• roughing: feed 0.08-0.15 mm/ tooth; speed 21-32 m/min
• finishing: feed 0.1-0.2 mm/ tooth; speed 41-67 m/min

End and slot milling with 1.3343 HSS:

• feed 0.03-0.10 mm/ tooth;
• speed 12-21 m/min

Band sawing nickel alloys:

• diameter 1.6 mm: 0.6 teeth/mm; speed 32 m/min
• diameter 6,4 mm: 0.4 teeth/mm; speed 23 m/min
• diameter 25 mm: 0.3 teeth/mm; speed 15 m/min
• diameter 76 mm: 0.2 teeth/mm; speed 15 m/min

Friction sawing nickel alloys:

• speed 3.1-5,5 m/min
• diameter 0.8 mm

Group B - easily machineable nickel alloys

This category includes nickel–copper and nickel–iron alloys. These alloys are highly resistant to seawater and sulfuric acid and are also used in the electrical industry. They have higher mechanical strength than pure nickel and are more readily strengthened by cold working. Most of these alloys cannot be hardened by heat treatment.

Sample alloys include:

Monel 400 - an extremely resistant to corrosion cracking copper-nickel alloy.  

Kovar - copper-nickel alloy with a very special thermal expansion characteristics.

General guidelines -  readily machined in any condition.

Boring and turning nickel alloys with high-speed steel:

• roughing: speed 27 m/min; feed 0.25 mm/rev
• finishing: speed 30 m/min; feed 0.13 mm/rev

Twist drilling nickel alloys with high-speed steel:

• drill D 1.6-3.2 mm
• speed 14-17 m/min
• feed 0.03-0.05 mm/rev

Tapping and threading nickel alloys with high-speed steel:

• tapping: feed 5-8 mm/rev
• threading: speed 7,6-9,1 m/min

Broaching nickel alloys with high-speed steel:

• speed 3.1-5,5 m/min
• angle 12-18°

Planing and shaping nickel alloys with high-speed steel:

• roughing: depth 16 mm; feed 0.13 mm; speed 12-15 m/min
• finishing: depth 0.25 mm; feed 6,35 mm; speed 12 m/min

Face and side milling with 1.3343 HSS:

• roughing: feed 0.18-0.25 mm/ tooth; speed 17-26 m/min
• finishing: feed 0.15-0.25 mm/ tooth; speed 24-53 m/min

End and slot milling with 1.3343 HSS:

• roughing: feed 0.03-0.10 mm/ tooth; speed 12.5-20 m/min
• finishing: feed 0.03-0.10 mm/ tooth; speed 46-76 m/min

Band sawing nickel alloys:

• diameter 1.6 mm: 0.7 teeth/mm; speed 38 m/min
• diameter 6,4 mm: 0.6 teeth/mm; speed 23 m/min
• diameter 25 mm: 0.4 teeth/mm; speed 15 m/min
• diameter 76 mm: 0.3 teeth/mm; speed 15 m/min

Friction sawing nickel alloys:

• speed 3.1-5,5 m/min
• diameter 5 mm

Group C - decently machineable nickel alloys

This category mainly includes heat-resistant and acid-resistant nickel–chromium and nickel–iron–chromium alloys. At room temperature, they have mechanical strength comparable to that of austenitic stainless steels.

Sample alloys include:

Inconel 600 - basic creep-resistant alloy.

Inconel 690 - Ni-Cr-Fe heat-resistant alloy, used in high-temperature Ni and Si environments.

Inconel 601 - basic creep-resistant alloy of good value.

Incoloy 825 - Ni-Cr-Fe-Mo alloy, good resistance to phosphorus acid, sulruric acid, intergranular corrosion and sulfide corrosion cracking.

Incoloy 800 - rather cheap creep-resistant alloy. 

General guidelines - can be machined in any condition.

Boring and turning nickel alloys with high-speed steel:

• roughing: speed 15 m/min; feed 0.25 mm/rev
• finishing: speed 18 m/min; feed 0.13 mm/rev

Twist drilling nickel alloys with high-speed steel:

• drill D 3.2-4.8 mm
• speed 8-11 m/min
• feed 0.05-0.10 mm/rev

Tapping and threading nickel alloys with high-speed steel:

• tapping: feed 3-5 mm/rev
• threading: speed 3.7-5,5 m/min

Broaching nickel alloys with high-speed steel:

• speed 1.5-3.7 m/min
• angle 10-15°

Planing and shaping nickel alloys with high-speed steel:

• roughing: depth 10 mm; feed 0.13 mm; speed 5-6 m/min
• finishing: depth 0.25 mm; feed 6,35 mm; speed 5 m/min

Face and side milling with 1.3343 HSS:

• roughing: feed 0.08-0.15 mm/ tooth; speed 6-11 m/min
• finishing: feed 0.10-0.15 mm/ tooth; speed 20-23 m/min

End and slot milling with 1.3343 HSS:

• roughing:feed 0.03-0.08 mm/ tooth; speed 5-8 m/min
• finishing: feed 0.03-0.10 mm/ tooth; speed 17-29 m/min

Band sawing nickel alloys:

• diameter 1.6 mm: 0.6 teeth/mm; speed 27 m/min
• diameter 6,4 mm: 0.5 teeth/mm; speed 23 m/min
• diameter 25 mm: 0.4 teeth/mm; speed 15 m/min
• diameter 76 mm: 0.3 teeth/mm; speed 15 m/min

Friction sawing nickel alloys:

• speed 1.5-3.7 m/min
• diameter 13 mm

Group D1 - nickel alloys easy to machine when in annealed condition

Some age-hardened nickel alloys are relatively easy to machine in annealed condition.

Sample alloys include:

Incoloy 925 anneled - corrosion-resistant alloy used widely in gas and oil industry.

Duranickel 301 annealed - low-alloy hardeanable nickel alloy.

Boring and turning nickel alloys in solution-annealed condition:

No working, High-speed steel:

• roughing: speed 12 m/min; feed 0.76 mm/rev
• finishing: speed 15 m/min; feed 0.2 mm/rev

No working, Carbide:

• roughing: speed 61 m/min; feed 0.51 mm/rev
• finishing: speed 76 m/min; feed 0.02 mm/rev

Cold work hardened, High-speed steel:

• roughing: speed 18 m/min; feed 0.25 mm/rev
• finishing: speed 21 m/min; feed 0.13 mm/rev

Cold work hardened, Carbide:

• roughing: speed 76 m/min; feed 0.25 mm/rev
• finishing: speed 91 m/min; feed 0.02 mm/rev

Twist drilling nickel alloys with high-speed steel:

• drill D 6.4-7.9 mm
• speed 6-9 m/min
• feed 0.08-0.13 mm/rev

Tapping and threading nickel alloys with high-speed steel:

• tapping: feed 3-5 mm/rev
• threading: speed 3.7-5,5 m/min

Broaching nickel alloys with high-speed steel:

• speed 1.5-3.7 m/min
• angle 10-15°

Planing and shaping nickel alloys with high-speed steel:

• roughing: depth 10 mm; feed 0.13 mm; speed 6-9 m/min
• finishing: depth 0.25 mm; feed 6,35 mm; speed 6 m/min

Face and side milling with 1.3343 HSS:

• roughing: feed 0.08-0.13mm/ tooth; speed 3-8 m/min
• finishing: feed 0.2-0.3 mm/ tooth; speed 20-21 m/min

End and slot milling with 1.3343 HSS:

• roughing:feed 0.03-0.08 mm/ tooth; speed 5-11 m/min
• finishing: feed 0.03-0.10 mm/ tooth; speed 34-58 m/min

Band sawing nickel alloys:

• diameter 1.6 mm: 0.7 teeth/mm; speed 23 m/min
• diameter 6,4 mm: 0.5 teeth/mm; speed 12 m/min
• diameter 25 mm: 0.4 teeth/mm; speed 9 m/min
• diameter 76 mm: 0.3 teeth/mm; speed 9 m/min

Friction sawing nickel alloys:

• speed 1.8 m/min
• diameter 25 mm

Group D2 - dificult to machine nickel alloys

This group includes D1 alloys in aged condition as well as many other age-hardenable alloys in any condition, and some highly solution-strengthened alloys.

Sample alloys include:

Incoloy 925 aged - described above.

Duranickel 301 aged - described above.

Hastelloy X - Ni-Cr-Fe-Mo alloy, solution-strengthened, used up to 1200°C.

Inconel 625 - creep and heat-resistant up to 825°C.

Inconel 725 - stronger Inconel 625 variant.

Inconel 718 - very popular superalloy, used in oil industry and aircrafts.

Hastelloy C-276 - highly corrosion resistant and weldable.

Inconel X-750 - used in gas turbines.

Alloy 901 - age-hardenable and used up to 600°C.

Alloy 617 - common creep-resistant alloy.

Alloy 90 (N07090) - creep-resistant up to 920°C.

General guidelines -  roughing should be conducted in annealed condition, and finishing in aged condition. A size contraction up to 0.07% takes place upon aging, which must be allowed for in rough machining.

Boring and turning nickel alloys I: roughing in annealed condition (85 HRB):

• High-speed steel: speed 5 m/min; feed 0.25 mm/rev
• Carbide: speed 23 m/min; feed 0.2 mm/rev
• Ceramic: speed 76-305 m/min; feed 0.25 mm/rev

Borind and turning nickel alloys II: finishing in hardened condition (45 HRC):

• High-speed steel: speed 5 m/min; feed 0.1 mm/rev
• Carbide: speed 34 m/min; feed 0.13 mm/rev
• Ceramic: speed 122-396 m/min; feed 0.1 mm/rev

Twist drilling nickel alloys with high-speed steel:

• annealed: drill D 9,5-11mm; speed 3-4 m/min; feed 0.10-0.18 mm/rev
• aged: drill D 13-17 mm; speed 2-3 m/min; feed 0.15-0.25 mm/rev

Tapping and threading nickel alloys with high-speed steel:

• tapping: feed 1.5-3 mm/rev; 
• threading: speed 0.9-1.1 m/min

Broaching nickel alloys with high-speed steel:

• speed 1.8 m/min
• angle 8-10°

Planing and shaping nickel alloys with high-speed steel:

• roughing, annealed: depth 10 mm; feed 0.13 mm; speed 1.5-3 m/min
• finishing: depth 0.25 mm; feed 6,35 mm; speed 1.5 m/min

Face and side milling with 1.3343 HSS:

• roughing: feed 0.08-0.13mm/ tooth; speed 3-8 m/min
• finishing: feed 0.2-0.3 mm/ tooth; speed 20-21 m/min

End and slot milling with 1.3343 HSS:

• roughing, annealed: feed 0.03-0.08 mm/ tooth; speed 3-6 m/min
• finishing, Aged: feed 0.03-0.10 mm/ tooth; speed 20-34 m/min

Group E - nickel alloys optimized for machineability

This group only has Monel R-405®, an alloy with S alloying addition, designed for easy machining and used for screws.

Boring and turning:

Annealed (65 HRB), High-speed steel:

• roughing: speed 21 m/min; feed 0.76 mm/rev
• finishing: speed 24 m/min; feed 0.2 mm/rev

Annealed, Carbide C-6:

• roughing: speed 84 m/min; feed 0.51 mm/rev
• finishing: speed 99 m/min; feed 0.02 mm/rev

Aged (100 HRB), High-speed steel:

• roughing: speed 37 m/min; feed 0.25 mm/rev
• finishing: speed 40 m/min; feed 0.13 mm/rev

Aged, Carbide:

• roughing: speed 107 m/min; feed 0.2 mm/rev
• finishing: speed 122 m/min; feed 0.1 mm/rev

Twist drilling with high-speed steel:

• speed 15-21 m/min
• feed 0.20-0.38 mm/rev