High Speed of (Ti-6Al-4V) Alloy

Anil Srivastava, Ph.D. Manager, Manufacturing Technology TechSolve, Inc., Cincinnati, OH 45237 Outline

• Applications of Titanium Alloys

• Technical Difficulties in Titanium Alloys

• High Speed Turning of Ti-6Al-4V Alloy

• Some Recent Test Results

• Conclusions

2 Application of Titanium Alloys

• Titanium and its alloys are today used in: – Aerospace – Medical device – Food and chemical industries

• Titanium alloys offers: – High strength-to-weight ratio – Super corrosion resistance – Bio-compatibility

• Titanium alloys are difficult-to-machine due to: – Low thermal conductivity and diffusivity – High rigidity and low elasticity modulus – High chemical reactivity at elevated temperatures – Work hardening characteristics

3 Machining Titanium for Economical Production BASIC RULES • Use low cutting speeds – a change from 6 to 46 meters per min (20 to 150 sfpm) with carbide tools results in a temperature change from

427°C to 927°C (800°F to 1700°F).

• Use high feed rates – a change from 0.05 to 0.51 mm/rev (0.002 to 0.020 in/rev) results in a temperature increase of only 149°C (300°F).

• Use generous amounts of cutting fluid – carries away heat, washes away chips, and reduces cutting forces.

• Use sharp tools – replace them at the first sign of wear, or as determined by production/cost considerations. Complete tool failure occurs rather quickly after small initial amount of wear takes place.

• Never stop feeding – while a tool and a workpiece are in moving contact. Permitting a tool to dwell in moving contact causes work hardening and promotes smearing, galling, seizing, and total tool breakdown. 4 (Courtesy of Supra Alloys, Inc.) Recent News

• Lockheed Martin has obtained government approval to use

‘cryogenic’ titanium machining process in production of the F-35 Lightning II stealth fighter that will improve tool-life by a factor of 10 with appropriate material removal processing speed.

• The Joint Program Office in coordination with the F-35 Fracture Control Board (FCB) approved the new process for standard roughing operations, impacting the most time-consuming and cost- intensive machining processes associated with manufacturing titanium parts.

• Broadly applied, this new technology could improve affordability and efficiency in the production of the F-35, which is approximately 25% titanium by weight.

American Manufacturing, September, 2011

5 Effect of Cutting Speed and Feed on Tool-Life

Table: Typical parameters for turning Ti-6Al-4V gas turbine components

CUTTING DEPTH OF TOOL FEED OPERATION SPEED CUT MATERIAL (in/rev) (SFPM) (in) Turn (Rough) C-2 150 0.010 0.250 Turn (Finish) C-2 200 0.006 - 0.008 0.010 - 0.030 Turn (Finish) C-2 300 0.006 - 0.008 0.010 - 0.030

(Courtesy of Supra Alloys, Inc.)

Figure: Effect of cutting speed and feed on tool-life when turning Ti-6Al-4V

6 Issues with Increasing Productivity and Possibilities

• In the past, improvement in cutting-tool performance by the application of coating technology has been very frustrating.

However, developments of interest include specially designed turning tools such as micro-edge geometry and new coatings.

• There seems to be great potential in machining of titanium with C-2 carbides when designed with proper geometry.

• Also, very little improvement in productivity has been experienced by exploring new combinations of machining parameters.

• Data is needed to determine the speeds at which reproducible and reliable tool life of the order of 5 to 10 min can be obtained, and to determine whether these conditions improve the economics of titanium machining.

7 High Speed Turning of Titanium (Ti-6Al-4V) Alloy Turning Test Conditions

• Work Material : Titanium (Ti-6Al-4V) Alloy Bar (2 in diameter) • Tool Holder : Type CTGPL 164 • Cutting Tool : Uncoated/Coated/Micro-edge/Super-finished Edge Geometry Carbide Inserts (TPG 432; Grade – K313) • Types of Coatings : TiAlN, [C8, C15, C2-SL Nano-Layers], and [#2390, #2391, #2393, #2414 Ultra-hard] • Cutting Speeds : 327 (100), 393 (120), 656 (200), 787 (240) SFPM(m/min) • Feed Rates : 0.002 (0.050), 0.003 (0.075), 0.004 (0.100), 0.005 (0.125) IPR (mm/rev.) • Depth of Cut : 0.040 (1.000) in (mm) • Cutting Fluid : few tests without coolant and few with flooded coolant application (Trim Sol – 5% vol.)

9 Turning of Titanium (Ti-6Al-4V) Alloy

Experimental Set-up for Turning Tests

10 Types of Nano-layered and Ultra-hard Coatings

Nano-layered Coatings:

1. C-8: TiAlSiCN based coating

2. C-15: CrAlSiN-CrAlSiYN based coating

3. C2-SL: TiAlN-CrN based coating

(All the three are PVD coatings)

Ultra-hard Coatings:

1. #2390: Multi-layer CrAlN coating

2. #2391: Multi-layer TiAlN coating Figure: High Magnification XTEM Bright Field Image of C2-SL Superlattice Coating.

3. #2393/#2414: HfB2 coating

(1 & 2 PVD; 3 is PVD+CVD coating)

11 Turning Test Results

1800 Uncoated Cutting Speed - 240 m/min 1600 C8 - Nanolayer Coated C15 - Nanolayer Coated

1400 C2-SL - Nanolayer Coated 1200 2390 Ultrahard Coated 2391 Ultrahard Coated 1000 2393 Ultrahard Coated

800 Variable Edge Prep

600

Average Cutting (N) ForceCutting Average 400

200

0 0.025 0.05 0.075 0.1 0.125 0.15

Feed Rate (mm/rev)

Figure: Effect of Feed Rate on Average Cutting Force

12 Turning Test Results

1400 Uncoated Cutting Speed - 200 m/min

C8 - Nanolayer Coated 1200

C15 - Nanolayer Coated (N) C2-SL - Nanolayer Coated 1000 2390 Ultrahard Coated 2391 Ultrahard Coated 800 2393 Ultrahard Coated Variable Edge Prep 600

400

Average Cutting ForceCutting Average 200

0 0.025 0.05 0.075 0.1 0.125 0.15

Feed Rate (mm/rev) 350 Cutting Speed - 120 m/min

300

(N) 250

200

150

100 Uncoated C8 - Nanolayer Coated C15 - Nanolayer Coated C2-SL - Nanolayer Coated 50 2390 Ultrahard Coated 2391 Ultrahard Coated

Average Cutting ForceCutting Average 2393 Ultrahard Coated Variable Edge Prep 0 0.025 0.05 0.075 0.1 0.125 0.15 Feed Rate (mm/rev)

Figure: Effect of Feed Rate on Average Cutting Force 13 Turning Test Results

1400 Uncoated Feed Rate - 0.125 mm/rev C8 - Nanolayer Coated

1200 C15 - Nanolayer Coated

C2-SL - Nanolayer Coated (N)

1000 2390 Ultrahard Coated 2391 Ultrahard Coated 800 2393 Ultrahard Coated Variable Edge Prep 600

400

200 Average Cutting ForceCutting Average 0 100 120 140 160 180 200 220 240

Cutting Speed (m/min) 1800 Uncoated

1600 C8 - Nanolayer Coated Feed Rate - 0.100 mm/rev

C15 - Nanolayer Coated (N) 1400 C2-SL - Nanolayer Coated 2390 Ultrahard Coated 1200 2391 Ultrahard Coated 1000 2393 Ultrahard Coated Variable Edge Prep 800 600 400

Average Cutting ForceCutting Average 200 0 100 120 140 160 180 200 220 240

Cutting Speed (m/min)

Figure: Effect of Cutting Speed on Average Cutting Force 14 Turning Test Results

1600 Feed Rate - 0.075 mm/rev 1400 Uncoated

(N) C8 - Nanolayer Coated

1200 C15 - Nanolayer Coated 1000 C2-SL - Nanolayer Coated 2390 Ultrahard Coated 2391 Ultrahard Coated 800 2393 Ultrahard Coated Variable Edge Prep 600

400

200 Average Cutting Force Cutting Average

0 100 120 140 160 180 200 220 240

Cutting Speed (m/min)

250

Feed Rate - 0.050 mm/rev

200

150

Uncoated 100 C8 - Nanolayer Coated

C15 - Nanolayer Coated Cutting Force (N) Force Cutting

C2-SL - Nanolayer Coated 2390 Ultrahard Coated 50 2391 Ultrahard Coated 2393 Ultrahard Coated

Variable Edge Prep Average 0 100 120 140 160 180 200 220 240

Cutting Speed (m/min)

Figure: Effect of Cutting Speed on Average Cutting Force 15 Turning Test Results

Uncoated C-8 Nano-layered # 2390 Ultrahard

C-15 Nano-layered #2393 Ultrahard

Cutting Speed: 240 m/min, Feed Rate: 0.100 mm/rev, Depth of Cut: 1.000 mm Figure: Tool Wear during Machining of Titanium (Ti-6Al-4V) Alloy

16 Turning Test Results

Uncoated C-8 Nano-layered # 2390 Ultrahard Uncoated C-8 Nano-layered # 2390 Ultrahard

C-15 Nano-layered C2-SL Nano-layered #2391 Ultrahard C-15 Nano-layered C2-SL Nano-layered #2391 Ultrahard

#2393 Ultrahard Variable Edge Prep #2393 Ultrahard Variable Edge Prep Cutting Speed : 240 m/min, Cutting Speed: 240 m/min, Feed Rate : 0.075 mm/rev, Feed Rate: 0.050 mm/rev, Depth of Cut : 1.000 mm Depth of Cut: 1.000 mm Figure: Tool Wear during Machining of Titanium (Ti-6Al-4V) Alloy

17 Turning Test Results

Uncoated C-8 Nano-layered # 2390 Ultrahard Uncoated C-8 Nanolayered C-15 Nanolayered

C-15 Nano-layered C2-SL Nano-layered #2391 Ultrahard

# 2390 Ultrahard #2391 Ultrahard #2393 Ultrahard

#2393 Ultrahard

Cutting Speed: 200 m/min, Cutting Speed: 200 m/min, Feed Rate: 0.125 mm/rev, Feed Rate: 0.100 mm/rev, Depth of Cut: 1.000 mm Depth of Cut: 1.000 mm Figure: Tool Wear during Machining of Titanium (Ti-6Al-4V) Alloy

18 Turning Test Results

Uncoated C-8 Nano-layered # 2390 Ultrahard Uncoated C-8 Nano-layered # 2390 Ultrahard

C-15 Nano-layered C2-SL Nano-layered #2391 Ultrahard C-15 Nano-layered C2-SL Nano-layered #2391 Ultrahard

#2393 Ultrahard Variable Edge Prep #2393 Ultrahard Variable Edge Prep

Cutting Speed: 200 m/min, Cutting Speed: 200 m/min, Feed Rate: 0.075 mm/rev, Feed Rate: 0.050 mm/rev, Depth of Cut: 1.000 mm Depth of Cut: 1.000 mm Figure: Tool Wear during Machining of Titanium (Ti-6Al-4V) Alloy

19 Turning Test Results

Uncoated C-8 Nano-layered # 2390 Ultrahard Uncoated C-8 Nano-layered # 2390 Ultrahard

C-15 Nanolayered C2-SL Nanolayered #2391 Ultrahard C-15 Nano-layered C2-SL Nano-layered #2391 Ultrahard

#2393 Ultrahard Variable Edge Prep #2393 Ultrahard Variable Edge Prep

Cutting Speed: 120 m/min, Cutting Speed: 120 m/min, Feed Rate: 0.125 mm/rev, Feed Rate: 0.100 mm/rev, Depth of Cut: 1.000 mm Depth of Cut: 1.000 mm Figure: Tool Wear during Machining of Titanium (Ti-6Al-4V) Alloy

20 Turning Test Results

Uncoated C-8 Nanolayered # 2390 Ultrahard Uncoated C-8 Nanolayered # 2390 Ultrahard

C-15 Nanolayered C2-SL Nanolayered #2391 Ultrahard C-15 Nano-layered C2-SL Nano-layered #2391 Ultrahard

#2393 Ultrahard Variable Edge Prep #2393 Ultrahard Variable Edge Prep

Cutting Speed: 120 m/min, Cutting Speed: 120 m/min, Feed Rate: 0.075 mm/rev, Feed Rate: 0.050 mm/rev, Depth of Cut: 1.000 mm Depth of Cut: 1.00 mm) Figure: Tool Wear during Machining of Titanium (Ti-6Al-4V) Alloy

21 The Micro Machining Process (MMP)

Figure: The Micro Machining Process (MMP) and Cutting Tool Super Finishing.

The lowest frequency range is the "Form" of the part, and this is what the designer sees on his CAD screen and is what he is ultimately trying to manufacture. Layered on top of the Form is the "Waviness", which is caused by the clearances built into the cutting machine that allow it to move freely. Layered on top of the Waviness is the "Primary Micro Roughness", which is normally attributed to the movement of the cutting tool as it removes material, and is usually similar in shape to the cutting tool geometry. Finally, layered on top of the Primary Micro Roughness is the "Secondary Micro Roughness", which results from the roughness on the surface of the cutting tool that was imparted on it during its manufacturing process and is now being transferred to the part being cut.

22 Friction at the Tool-Work-Chip Interface

Figure: Effect of Feed Rate on the Coefficient of Friction (with/without coolant application)

23 Turning Test Results

Cutting Speed: 100 m/min, Feed-Rate: 0.075 mm/rev, Depth of Cut: 1.000 mm, Coolant: (5% vol.) Trim Sol

Figure: Maximum Tool-Wear v/s Machining Time

24 Turning Test Results

0.6 Uncoated (K313) Coated C-8 Coated C-15 Coated C2-SL Superfinish Coated C-16 Ultrahard #2390 Ultrahard #2391 Ultrahard 2414 (2393)

0.5

Uncoated (K313) Coated C-16 0.4 Coated C- 8 Ultrahard # 2391

0.3 Ultra-hard # 2414 (2393) Coated C2 -SL

0.2 Coated C-15 Maximum Tool(mm) Wear Maximum Ultrahard # 2390 0.1 Super-finished Cutting Edge

0 0 5 10 15 20 25 30 35 40 45 50

Cutting Time (min)

Cutting Speed - 120 m/min; Feed Rate - 0.075 mm/rev; Depth of Cut - 1.000 mm, Cutting Fluid - Trim Sol (5% vol.) Figure: Maximum Tool -Wear v/s Machining Time

25 Magnetic Field Assisted Super-Finishing

Figure: Magnetic Field Assisted Super-Finishing of Carbide Insert

(Courtesy of University of Florida, Gainesville, FL)

26 Edges of Carbide Inserts Super-Finished

27 Insert Surface-Finish Measurement

28 Polished Surface Roughness

29 Some Recent Turning Test Results

30 Conclusions and Future Work

• Several oblique (3-D) turning tests have been conducted using uncoated, coated, cutting edge having micro-edge geometry, and super-finished cutting edge carbide inserts.

• It seems that a few coatings may prove to be a good candidate for machining of Titanium alloys.

• Super-finished cutting edge inserts show enhanced (~2X) tool life in comparison to other uncoated and coated inserts.

• Further experiments are being conducted using super-finished edged cutting tools with the goal of optimizing the level of super- finishing that will provide maximum enhancement in tool-life and productivity while turning Ti-6Al-4V Titanium alloy.

31 Acknowledgment

• TechSolve wishes to thank Professor Hitomi, University of Florida, Gainesville, FL; MicroTek & UES, Inc., OH; Richter Precision Inc. & Conicity Technologies, PA for providing ultra- hard, nano-layered coated, special micro-edge and super-finished cutting edge prep inserts used for this study.

• Special thanks to National Science Foundation (NSF) for supporting this research under the Award No. 0757954.

32 Thank You ! ?