Failure Analysis of H13 Tool Steel in Aluminum Extrusion Dies

1
Failure Analysis of H13 Tool Steel in Aluminum
Extrusion Dies

• Mesut Varlioglu, Taehyung Kim
• Joseph Benedyk, Philip Nash, Sheldon Mostovoy
• Thermal Processing Technology Center
• 01/30/04

2
Agenda

• Fracture Surface Analysis
• On Aluminum exposed die.
• Rising Load Test Results
• All samples machined.
• Coating the die
• The common applications in the extrusion
  facilities.
• Pearlite Study
• Study for grain size with different
  austenitization temperature.

3
Fracture Surface Analysis for the die exposed to
aluminum.
The previous crack surface investigation was done
with the dies exposed to caustic. A slice with 10
mm thick from the center of the die was cut.
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1
Die parts after cutting operation.
The Die piece. Red circles show the area observed
in SEM.
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SEM Pictures
1
2
3
7 6 5 4 3 1 2 8 9
Area 1 Area 2
The chemical distributions of Zn and Al in the
interface of fracture and interaction area.
With poor precision.
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Fracture Analysis for Al Exposed Die
Aluminum
H13
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SEM Analysis inside
Mounting Material
H-13
10
9
8
1
11
12
2
3
4
5
6
7
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Surface Analysis of the extrusion material
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1
Inside of the extrusion material.
Material surface.
Chemical compositions of two points. With poor
precision.
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Step Loading Test Procedure

• The tensile test specimen that has a cylinder
  gap inside is filled with 7XXX series Al alloy
  and heated in 550 C.
• Then, the inside part is closed with a screw.
• In the high temperature tensile test machine,
  the specimen is heated at around 550 C and
  started to load at P/8 in each cycles in 8 hour
  period.
• Then the data from the specimen filled with
  other substances including air is compared. Also,
  the fracture surface is compared with the real
  fracture surface of the bridge of the die.

Source ASTM F 1624-95.
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Specimen Shape
Specimen cross section was calculated for 200 ksi
tensile strength and 12 kips max. load for the
Instron Machine.
19/64 in.
Specimen after machined.
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Heat Treatment and Test Conditions

• Heat Treatment
• Atmosphere Nitrogen.
• Austenitization Temperature 1850 F, 1 hour.
• Hardness 52 HRC.
• Tempering Temperature 1100 F, 6 hrs.
• Hardness 49 HRC.
• Rising Load Test
• Loading Rate 5 lbs/s.
• Test Temperature 521 C.
• Load in each step 1.5 kips (8 steps).

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First Test Result
Stress 142 ksi No fracture.
Load vs. Time
Load vs. Displacement
Test material H13 filled with 7116 Al alloy.
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Second Test
Stress 180 ksi Fracture
after 9.8 hours.
Load vs. Time
Mechanical properties of H13 at 550 C
Source ASM Specialty Handbook, Tool Materials,
1995, p.140-141.
Same Sample.
Load vs. Displacement
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3 Sample Conditions
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Test Results
Stress 237.5 ksi
Load vs. Time
Stress 88 ksi
Load vs. Displacement.
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Samples after the test
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COATING THE DIE
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External Coating
Surface Treatments
External Coating
Die surface is modified

• Chemical Vapor Deposition
• (CVD)
• Physical Vapor Deposition
• (PVD)
• Ex. TiC, TiN, TiC/TiN, CrN and TiAlN etc.

Nitriding
Carbo-Nitriding

• Gas nitriding
• Salt Bath nitriding
• Fluidised Bed Nitriding
• Plasma (ion) nitriding

• Die life extends up to 5 times for gas nitrided
  dies and 7 or 8 times for ion nitriding, compared
  to untreated dies.

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Die Service Cycle
Typical Flow Chart of the Die Circulation in the
Extrusion Plant2.
Typical Depth and Hardness Layer or Coating for
Different Methods of Surface Engineering1.
1 Kelley I.B., Plasma Sprayed Ceramic Coatings
for Extrusion Dies, 1996. 2 Czelusniak A.,
Influence of Die Handling Operations on
Performance of Nitrided Aluminum Extrusion Dies,
1996.
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Coating Layer
Some typical coating types. Mew A.B., The
Evaluation of Some Surface Treatments for
Aluminum Extrusion Dies, 1998.
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Pearlite Study
Grain size was tried to calculated in this
reseach. Austenitization Temp. 1750 F, 1850 F,
1950 F 1 hour 1400 F in 13-15 min to hit pearlite
nose. Then air cool.
Source Ray Reynoldson, The Heat Treatment of
Extrusion Tools Using Fluidized Bed Technology,
ET 1996 Seminar.
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Micrographs
1750 F, 1000 x.
1850 F, 1000x. ASTM Grain Size 10.52

1950 F, 1000x. ASTM Grain Size 9.74
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Alternative for U-Bend Device
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FUTURE WORK

• To continue the SEM analysis on the die not
  exposed to caustic.
• To continue the metallographic method for
  revealing the retained austenite and compare the
  results with other dies as well as Rising Load
  Test specimens.
• Duplicate the rising load test results by using
  different filling material, testing temperature,
  loading rate.
• Continue investigating fracture surfaces in
  different dies.