Understanding the
Explosion Clad Interface CURTIS PROTHE Chief Technologist DMC Clad Metal Mt. Braddock, PA STEPHEN LIU, PHD Professor of Metallurgical and Materials Engineering Colorado School of Mines Golden, CO JOHN BANKER Vice President DMC Clad Metal Boulder, CO CORROSION SOLUTIONS 2011 Understanding the Explosion Clad Interface Characteriza*on conducted at the Shared Research Equipment (SHaRE) User Facility at Oak Ridge Na*onal Laboratory • Ed Kenik • Chad Parish CORROSION SOLUTIONS 2011 Understanding the Explosion Clad Interface TOPICS Ø Introduc*on Ø Macro – Micro-­‐Scale Observa*ons Ø Nano-­‐Scale Interface Characteriza*on • Stainless Steel – Carbon Steel • Copper – Carbon Steel • Titanium – Carbon Steel • Titanium -­‐ Nickel Ø Conclusions CORROSION SOLUTIONS 2011 Explosion Welding In EXW the metals to be welded are propelled together in a high velocity angular collision which results in welding. CORROSION SOLUTIONS 2011 Explosion Welding Pre-clad Assembly
Explosion Cladding Event
Ø Cladding and Base Metal Plates are posi*oned parallel with a preset separa*on distance. Ø Detona*on sweeps across the plate at ~ 2500 m/sec Ø Explosive is placed on top Ø Welding of a 2.5m x 6m plate occurs in ~ 1.5 x 10(-­‐3) second CORROSION SOLUTIONS 2011 Explosion Welding A3ributes Ø Cold Welding Technology -­‐ Bulk metal proper*es are not altered by Detaclad® opera*on • Corrosion resistance • Mechanical proper*es Ø Produces a strong, duc*le, con*nuous metallurgical weld over full surface Ø Virtually any metal combina*on can be welded • Dissimilar alloys, such as Ti or Al to Steel • Similar alloys, such as Stainless Steel to Steel CORROSION SOLUTIONS 2011 Explosion Welding A3ributes Ø Cold Welding Technology -­‐ Bulk metal proper*es are not altered by Detaclad® opera*on • Corrosion resistance • Mechanical proper*es Ø Produces a strong, duc*le, con*nuous metallurgical weld over full surface Ø Virtually any metal combina*on can be welded • Dissimilar alloys, such as Ti or Al to Steel • Similar alloys, such as Stainless Steel to Steel v EXW a3ributes are the results of the structure, composi?on and nature of the EXW interface CORROSION SOLUTIONS 2011 Understanding the Explosion Clad Interface CORROSION SOLUTIONS 2011 Understanding the Explosion Clad Interface Macro – Micro-­‐scale Observa?ons Ø Most EXW product exhibits characteris*c wavy interface • Hydrodynamic instability mechanism • Shear flow near collision point – results in jeang • Plas*c deforma*on (cold work) • Entrapped jet, melt pockets may be present Stainless Steel Mild Steel
CORROSION SOLUTIONS 2011 Understanding the Explosion Clad Interface Macro-­‐scale Observa?ons • Wave pabern observed depends on angle of intersec*on of the cut edge and direc*on of explosive detona*on CORROSION SOLUTIONS 2011 Understanding the Explosion Clad Interface Micro-­‐scale Observa?ons Ø Wave morphology can vary greatly depending on alloys and EXW parameters Low VOD Produc*on Parameters
Low Standoff
Grade 1 Titanium – Mild Steel, 100X High VOD High Standoff CORROSION SOLUTIONS 2011 Understanding the Explosion Clad Interface Stainless Steel Extensive
plastic
deformation
greatly
increased the
spacing
between
pearlite
colonies near
the dissimilar
metal bond
interface.
Mild Steel Pearlite
lamellae
rotated with
deformation
CORROSION SOLUTIONS 2011 &>67T:5>83'!1>B>5;3B2U>V76''T''$$'W'!$'''
Foils extracted by focused ion beam
(FIB) from the crest of the waves
Stainless Steel
Mild Steel
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L3G-6(%$+@$#5"-+K-00I!0-(,&'$K#%'Foils extracted by focused ion beam (FIB)
from the crest of the waves & observed
under TEM
Original magnification of 4200X
Stainless Steel
!/-
Stainless Steel
F,&'$K#%(#<-$'@(+,-
0&''<Bond
Interface
Mild Steel
Mild Steel
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Nano-­‐scale CharacterizaVon -­‐ SS / CS TEM micrograph of SS-­‐CS interface Original
magnification
of 4200X
Stainless
Steel
• The thermal condi*ons adjacent to Stainless Steel
the bond interface were such that recrystalliza*on occurred with regular shaped and fine sized grains (100 – 300 nm) Bond
on both sides of the Interface
Mild Steel
bond. Stainless Steel
Mild Steel
Mild Steel
CORROSION SOLUTIONS 2011 Nano-­‐scale CharacterizaVon -­‐ SS / CS High Magnifica*on EDX scan •  EDX scan of the Stainless Steel-Mild Steel bond
interface. A sharp composition (Cr, Ni, and Fe)
gradient was observed. The red line shows the
scan.
•  The width of the Stainless Steel-Mild Steel
gradient zone is only approximately 20 nm.
Stainless Steel
Mild Steel
CORROSION SOLUTIONS 2011 &>67T:5>83'!1>B>5;3B2U>V76''T''!F'W'!$'''
Foils extracted
by focused ion
beam (FIB) from
the crest of the
waves for
observation
under TEM
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L3G-6(%$+@$#5"-+K-!/I0&''<-(,&'$K#%'Original Magnification: 7300X
Original Magnification: 22000X
0&''<-
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Nano-­‐scale CharacterizaVon -­‐ Cu / CS • Elongated grains of
width around 100nm on
the steel side indicates
high degree of
deformation.
• Equiaxed submicron
grain structure on the
copper side indicates
some degrees of
recrystallization. The
melting temperature of
Copper is about 450oC
lower than steel.
Cu Interfacial region Steel CORROSION SOLUTIONS 2011 &>67T:5>83'!1>B>5;3B2U>V76''T''!F'W'!$'''
3M^-@$#.(',&-+K-&"'-!/I!0-(,&'$K#%'•! Sharp composition gradient was observed.
Copper and iron decreased sharply from
either side of the interface.
•! The width of the Cu-Fe gradient zone is
approximately 20 nm.
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0&''<-
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Nano-­‐scale CharacterizaVon -­‐ Ti / CS • Ti / CS As-­‐Clad Foils extracted by focused ion beam (FIB) from the
crest of the waves for observation under TEM
CORROSION SOLUTIONS 2011 Nano-­‐scale CharacterizaVon -­‐ Ti / CS EDX gradient of the as-­‐clad Ti-­‐CS interface •  Sharp composition gradient was observed.
•  The width of the Ti-Fe gradient zone is
approximately 120 nm.
Element Line KRa*o Correc*on Overvoltage Weight % Atoms % Ti Ka 0.631±0.0136 1.0000 0.00 63.11±1.36 66.61±1.43 Fe Ka 0.369±0.0127 1.0000 0.00 36.89±1.27 33.39±1.15 CORROSION SOLUTIONS 2011 &>67T:5>83'!1>B>5;3B2U>V76''T''*2'W'!$'''
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Nano-­‐scale CharacterizaVon -­‐ Ti / CS Ti / CS Stress Relief HT, 607°C (1125°F), 2hrs CORROSION SOLUTIONS 2011 Nano-­‐scale CharacterizaVon -­‐ Ti / CS Ti / CS Stress Relief HT, 607°C (1125°F), 2hrs CORROSION SOLUTIONS 2011 Nano-­‐scale CharacterizaVon -­‐ Ti / CS EDX gradient of the SRHT Ti-­‐CS interface •  Rather sharp composition gradient was
observed.
•  The width of the Ti-Fe gradient zone is
approximately 160 nm.
Element Line KRa*o Correc*on Overvoltage Weight % Atoms % Mn Ka 0.034±0.0022 1.0000 0.00 3.38±0.22 3.07±0.20 Fe Ka 0.248±0.0054 1.0000 0.00 24.84±0.54 22.18±0.48 Ti Ka 0.718±0.0076 1.0000 0.00 71.79±0.76 74.75±0.79 CORROSION SOLUTIONS 2011 Nano-­‐scale CharacterizaVon -­‐ Ti / Ni Foils extracted by
focused ion beam (FIB)
from the crest of the
waves for observation
under TEM
CORROSION SOLUTIONS 2011 Nano-­‐scale CharacterizaVon -­‐ Ti / Ni EDX gradient of the as-­‐clad Ti-­‐Ni interface •  Sharp composition gradient was observed.
•  Tilted boundary or separate layer?
•  The width of the Ti-Ni gradient zone is
approximately 160 nm.
CORROSION SOLUTIONS 2011 Nano-­‐scale CharacterizaVon -­‐ Ti / Ni Ti / Ni Stress Relief HT, 607°C (1125°F), 2hrs CORROSION SOLUTIONS 2011 &>67T:5>83'!1>B>5;3B2U>V76''T''*2'W'&2'
3M^-@$#.(',&-+K-&"'-018L-L(IA(-(,&'$K#%'•! Sharp composition gradient was observed.
•! Two distinct, well defined intermetalic layers,
TiNi3, TiNi.
•! The width of the Ti-Ni gradient zone is now
approximately 2500 - 3000 nm
(15x
+ as-clad width).
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Understanding the Explosion Clad Interface CONCLUSION • The interface region is very sharp and fine for all clad materials studied Ø Stainless Steel – Carbon Steel Ø Copper – Carbon Steel
Ø Titanium – Carbon Steel as-­‐clad
Ø Titanium – Nickel as-­‐clad
Ø Titanium – Carbon Steel SRHT
~20-­‐40 nm ~20 nm ~120 nm ~160 nm ~160 nm Very fine Ti grains nucleated at interface boundary Ø Titanium – Nickel SRHT
~2500 -­‐ 3000 nm Significant interface growth with dis8nct intermetallic phases • Interface appears to be amorphous and/or nanocrystalline CORROSION SOLUTIONS 2011 Understanding the Explosion Clad Interface CONCLUSION • On the micro-­‐scale plas*c flow is observed near the bond interface • Regular shaped and fine grains (100 – 300 nm) indica*ve of recrystalliza*on were observed on both sides of the bond on the nano-­‐scale. • The structure, composi*on and nature of the interface determine the EXW proper*es and abributes. Ø The thin, rapidly solidified, metastable interface enables welding of highly dissimilar metals (Ti / CS) CORROSION SOLUTIONS 2011 Understanding the Explosion Clad Interface CONCLUSION • Ongoing study supports understanding of the explosion welding process Ø Inves*gate EXW parameters Ø Addi*onal clad materials and heat treatment condi*ons CORROSION SOLUTIONS 2011