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© by Walter AG Titanium USA 2015 Kevin Maples Advancements in Insert Cutting Edges and Coatings
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Titanium USA 2015
Kevin Maples
Advancements in Insert Cutting Edges and Coatings
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New Geometries for the Titanium Industry
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• Demands Regarding the Machining of Titanium– Decrease of production costs– Increase of the process reliability– High, guaranteed tool life– Machinability at combinations of
– High tensile strength or hardness – High toughness– High share of alloyed material
– More applications of those materials (e.g..):– Mechanical engineering (propulsion, e.g.. Turbine blades)– Process engineering e.g.. valves
Needs of the market
K. Maples| RCC - SAM| 6 October 2015
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New Geometries for the Titanium Industry
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Why do we need new geometries
Characteristics of Machining Titanium• High load and high temperatures in a small area along the cutting edge • Cutting edge is heavily loaded (forces and temperature)• Smaller chip compression:
- Longer chips compared to steel- Thinner chips
• The temperature is dissipated mainly through the cutting edge (steel rough the chips)
• Possible feed per tooth (chip thickness) << steel• Higher demands on run out• Only a few geometries are functional (otherwise dramatic short tool life)
K. Maples| RCC - SAM| 6 October 2015
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Titanium Alloy Machining
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Metal cutting characteristics of titanium and titanium alloys
• The cutting edge of the tool is subject to high thermal loads due to the relatively low thermal conductivity and density of titanium.
• Due to its low modulus of elasticity, titanium yields under the pressure of the cutting tool.
• Titanium shows a chemical reactivity with cutting tool materials at high temperatures.
• Titanium tends to weld on the tool rake face.
• Titanium generates a cyclic chip formation.
K. Maples| RCC - SAM| 6 October 2015
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Chip Formation Titanium Alloys
4K. Maples| RCC - SAM| 6 October 2015
Titanium alloys and Nickel based alloys• Chip thickness h1 ≈ Chipping thickness h• Small contact area• High cutting forces• High temperature• Bad thermal conductivity• The biggest part of the temperature is transported
via the cutting edge High forces and high temperature on a small
part of the cutting edge. The geometry in the area of the cutting edge
is the deciding factor!
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Chip Formation Titanium Alloys
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Quelle: IPT-AIF-Zutech
Behavior of Material Group
• Low thermal conductivity
• High tensile strength combined with toughness
• Chemical reaction under high temperature
• Small E-modulus ("Young's modulus“) with titanium
S
K. Maples| RCC - SAM| 6 October 2015
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Coating Processes
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There are two different coating processes:
– CVD coating is a chemical process that is used on carbide indexable inserts with cutting edges that are less sharp.
– PVD coating is a physical process that is used on carbide indexable inserts with sharp cutting edges.
During CVD coating, a gas mixture is evaporated onto the carbide indexable insert, therefore forming the coating layer. The process takes place in a coating furnace at temperatures of 800 °C to 1,100 °C. The layer thicknesses that are applied varybetween 6 μm and 20 μm, depending on the carbide grade.
During PVD coating, the coating materials are atomized and the electrically charged atoms are attracted by the carbide indexable inserts in a high-vacuum coating system. The coating thicknesses that are applied vary between 1 μm and 4 μm, depending on the carbide grade.
K. Maples| RCC - SAM| 6 October 2015
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Coatings
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PVD CVD
Coating Temperatiure 400 – 600 °C 800 – 1100 °C
Toughness
Residual stresses Compressive Stresses Tensile Stresses
Layer Connection
crystallite Nano- to fine crystalline fine crystalline
chemical stability metastable phases most thermodynamically stable phases
High Temperaturewear resistance
layer thickness 2 – 5 µm 5 – 20 µm
K. Maples| RCC - SAM| 6 October 2015
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Substrates
K. Maples| RCC - SAM| 6 October 2015 8
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Coating Design, PVD vs CVD
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Post treatment2nd generation
K. Maples| RCC - SAM| 6 October 2015
7 µm
PVD CVD
Al2O3
TiAlN
Substrate(Carbide)
TiAlN/Al2O3Multilayer
Post treatment
Indicator Layer(Appearance, wear detection)
3 µm
TiCN-decor flank face
α-Al2O3
Bondinglayer
MT-TiCN
TiN
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Coating and Grade Testing
Drobniewski | VR | 17. June 2015 10
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Wear Forms
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Reason:Wear Form : Impact:
• Vc
• Use of a different insert grade and firmer carbideFlank Wear
• Abrasive wear is the most common form of wear when machining stainless steels
• Mainly caused in materials with a high Cr content (carbides)
• Possible burrs and poor component surface finish
• Short cutting edge life
• Dimensional inaccuracy of the components
Remedy:
K. Maples| RCC - SAM| 6 October 2015
Adhesion
• High material affinity (attraction) may lead to built-up edge
• Mainly high-alloy steels with high Ni content
• The built-up edge can cause delamination and chipping.
• The built-up edge can the work harden the part surface influencing and deteriorating the part surface finish
• Uneven chip formation
• Built-up on leading edge
• Vc
• Increase coolant concentration
• Verify correct cutting edge (Micro Geometry)
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Field Test
12K. Maples| RCC - SAM| 6 October 2015
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Field Test
13K. Maples| RCC - SAM| 6 October 2015
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Field Test
Drobniewski | VR | 17. June 2015 14
3 5
12
3 1
Ti6Al4V 200 255
0.0050 6.4
1.06 6.8
19.1 0.80
15.3 2521.0 3781.5 315.1
30252.2 2521.0
60 mins 0.01" to 0.015" Very Minor
DIA (in) 3# EDGES 5GL (in) 12
DOC (in) 3WOC (in) 1
WORKPIECE Ti6Al4VSFM (ft/min) 140RPM (rev/min) 178
APT (in) 0.0040IPM (in/min) [NO THINNING] 3.6Chip Thinning Multiplier 1.06IPM (in/min) [WITH THINNING] 3.8
MRR (in3/min) 10.7K (Hp min/in3) 0.80HP 8.6Ft (lbf) 2016.8T (in lb) 3025.2T (ft lb) 252.1Bm (in lb) 24201.7Bm (ft lb) 2016.8
PERFORMANCETime in Cut 60 minsFlank Wear 0.01" to 0.015"Chipping Very Minor
CURRENTDIA (in) 3# EDGES 5GL (in) 12
DOC (in) 3WOC (in) 1
WORKPIECE Ti6Al4VSFM (ft/min) 175RPM (rev/min) 223
APT (in) 0.0050IPM (in/min) [NO THINNING] 5.6Chip Thinning Multiplier 1.06IPM (in/min) [WITH THINNING] 5.9
MRR (in3/min) 16.7K (Hp min/in3) 0.80HP 13.4Ft (lbf) 2521.0T (in lb) 3781.5T (ft lb) 315.1Bm (in lb) 30252.2Bm (ft lb) 2521.0
60 mins 0.01" to 0.015" Very Minor
FUTURE CHALLENGE
MEETSEXPECTATIONS
EXCEEDSEXPECTATIONS
WALTER RESULTSDIA (in) 3# EDGES 6GL (in) 7.25
DOC (in) 3WOC (in) 1
WORKPIECE Ti6Al4VSFM (ft/min) 175RPM (rev/min) 223
APT (in) 0.0060IPM (in/min) NO THINNING 8.021Chip Thinning Multiplier 1.06
IPM (in/min) WITH THINNING 8.502
MRR (in3/min) 24.1
HP 28.3F1 (lbf) 2521T (in lbs) 7393.44T (ft lbs) 666.12Bm (in lbs) 30252.2Bm (ft lbs) 2521
PERFORMANCETime in Cut 67.4 minsFlank Wear 0.004" - 0.0055"
Chipping Very Minor
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Summarization
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Grade development and cutting edge preparation are key factors when machining Titanium.
A higher degree of “rake” angle is required to form a chip. Honing or “rounding” the cutting edge helps protect the insert
from chipping and notching. Coolant concentration is a key factor in chip removal and
cooling. For Titanium machining the coolant concentration should be
10 - 12% when mixed with water.
K. Maples| RCC - SAM| 6 October 2015
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Engineering Kompetenz
Thank you
