Upload
hoangque
View
214
Download
0
Embed Size (px)
Citation preview
EOT_RT_Sub_Template.ppt | 1/6/2009 | 1BOEING is a trademark of Boeing Management Company.Copyright © 2009 Boeing. All rights reserved.
Failure Analysis of a Gas-Nitrided 15-5PH SteelJ. L. Golden, Ph.D.ASM Houston Chapter / Failure Analysis SeminarHouston, TX03 April 2012
https://ntrs.nasa.gov/search.jsp?R=20120003598 2018-05-22T13:48:56+00:00Z
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 2
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Failure Analysis of Gas-Nitrided 15-5PH Steel
• Acknowledgements• All Boeing and Boeing subcontractor activity conduc ted
under NASA contract– NAS15-10000
• Intense Team Effort, conducted from October 2007 th rough January 2010.
– NASA JSC ES4– NASA MSFC EM30– NASA KSC NE– NASA Engineering & Safety Center (NESC)– Boeing– Lockheed-Martin– ATK– Numerous Supportive Subcontractors
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 3
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Failure Analysis of Gas-Nitrided 15-5PH Steel
Summary of Presentation• Brief Background on the Failure
• International Space Station; Solar Alpha Rotary Joi nt• “What do you do when you cannot get at the hardware ?”
• Failure Analysis Approach• Sampling Failed Surface and Microscopy/Metallograph y• Review of All Acceptance Data• Sampling of Production Witness Specimens• Sampling on Engineering Development and Spare Parts• Production of Test Articles for Mechanical Test in an Attempt
to Duplicate Flight System Failure– Use as high a fidelity as is reasonable– Nitrided 15-5PH steel (same steel spec., same heat treatment,
same nitriding process and processor).– IVD gold coating on 440C (roller simulation with sa me process
and processor)– Comparable mechanism kinematics
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 4
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Failure Analysis of Gas-Nitrided 15-5PH Steel
ISS 2007 Configuration: Solar Alpha Rotary Joint (SARJ) Locations
Port SARJ
Starboard SARJ (failed)
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 5
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Failure Analysis of Gas-Nitrided 15-5PH Steel
The Solar Alpha Rotary Joint (SARJ) is used to rotate the outboard Solar Array Wings (SAW) and transfer
generated power to the ISS pressurized elements
SEGMENT(P3/S3)
SEGMENT(P4/S4)
SARJ
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 6
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Failure Analysis of Gas-Nitrided 15-5PH Steel
Nitrided 15-5PH
Race RingIn
ner 4
5
Datum A
Outer 45
Race Ring
Trundle Bearing Assembly
Inboard Arm
Camber Pivot
Fixed Arm
Trundle Mounting Clamp
Camber Pivot
Camber Pivot
440C Stainless Rollers
w/Au plating
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 7
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Failure Analysis of Gas-Nitrided 15-5PH Steel
Initial Examination of Starboard SARJ Race Ring Damage
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 8
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Failure Analysis of Gas-Nitrided 15-5PH Steel
• Physical Characteristics of the Failure Debris• Particle Size Distribution
s-SARJ Debris Total Surface Area vs. Particle Size
0
50000
100000
150000
200000
250000
300000
350000
400000
450000
0 100 200 300 400 500 600 700 800
Feret Diameter (µm) - Bin
Tot
al S
urfa
ce A
rea
(m
2 )
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 9
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
• Physical Characteristics of the Failure Debris – Con t.• Particle Size Distribution – Both views are 100X
Failure Analysis of Gas-Nitrided 15-5PH Steel
Representative area of“fine” debris (< 100 µm)
Representative area of all debris;broad particle size distribution
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 10
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
• Physical Characteristics of the Failure Debris – Con t.• Particle Types – Agglomeration Particles
Failure Analysis of Gas-Nitrided 15-5PH Steel
Nitrided 15-5 PH agglomerated fragment from Tape 31 imaged under high vacuum. Reference magnifications: 100X (left), 500X (right)
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 11
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
• Physical Characteristics of the Failure Debris – Con t.• Particle Types – “Large Chip” Particles
– Original surface typically visible on one side (rig ht photo)– Low cycle subsurface fractures on the other (left p hoto)– Thickness typically at or near nitride layer thickn ess
Failure Analysis of Gas-Nitrided 15-5PH Steel
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 12
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Failure Analysis of Gas-Nitrided 15-5PH Steel
• Physical Characteristics of the Failure Debris – Con t.• Fracture Surfaces on “Chip” Particles – Continued
• Largest particle located was ~3mm x ~5 mm.
• Particle thickness was about 150-170 µµµµm, essentially equal to the nitride layer thickness.
• Numerous subsurface fracture initiation sites were observed, indicating a low-cycle fracture phenomenon took place.
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 13
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
• Physical Characteristics of the Failure Debris – Con t.• “Chip” Particles In Cross-Section
Failure Analysis of Gas-Nitrided 15-5PH Steel
Typical large “chip” cross section showing:• Maximum thickness essentially equivalent to nitride layer thickness, indicating
failure is occurring near the case/core interface;• Evidence of residual “white layer”, in excess of the 8 µµµµm maximum required.• Fracture lines are transgranular, showing no preference for the intergranular
networking observed near the surface.
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 14
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
• We observed Discontinuous Intergranular Separations (DIGS) in the nitride layer on our 15-5PH steel
• Once the decision was made to surface harden the SA RJ race rings, the gas nitriding process was geared toward producing a nitride layer of 150 µµµµm minimum in a relatively short time (36 hours).
– Principal means used to accomplish these goals was with the use of an activator.
• Our team’s theory is that nitrogen supersaturation o f the 15-5PH steel surface occurred, which on cooling led to separations forming along some grain boundaries in the outer 50 µµµµm of the surface.
• Differences in DIGS concentration appears to be rel ated to the amount of activator used during the heat treatment.
– Thirty percent more activator was used on the Starb oard SARJ race ring than was used for the Port race ring.
Failure Analysis of Gas-Nitrided 15-5PH Steel
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 15
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
• How did we miss the DIGS originally?• They were right in front of us, but not recognized as an issue.• Micrograph below is from original test coupon inspe ction.
Failure Analysis of Gas-Nitrided 15-5PH Steel
CASE COREWHITELAYER
INTER-GRANULARNETWORKING
DIGS
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 16
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Failure Analysis of Gas-Nitrided 15-5PH Steel
Nitride Control Coupon (NCC) –Nitrided in same furnace as the flight
SARJ race ring, at fixed locations .
Metallurgical Evaluation of SARJ Race Ring S/N 4Sample Coupon (Polished, Etched and View @1000X)
Networking
Intergranular separations(appear like cracks)
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 17
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Failure Analysis of Gas-Nitrided 15-5PH Steel
Separation / void
Networking
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 18
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Failure Analysis of Gas-Nitrided 15-5PH Steel
Polished metallographic sample exhibiting DIGS. The degree of porosity and the type scaffolding
structure remaining inside each DIGS varies and at times appears as a nanostructure.
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 19
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
• What happened to the SARJ “as-designed” lubrication system?
• The sole lubrication between trundle rollers and th e nitrided race ring was 1500-2000Å of gold deposited on the 44 0C rollers by ion plating.
• Ground testing (in retrospect, inadequate and misle ading) indicated that this lubrication design was sufficie nt to protectthe nitrided 15-5PH steel race ring surface.
• In addition, the ground environment was undermining the lubrication system by deteriorating the plating adh esion (see the following charts).
• Once the transfer-film lubricant was lost, the kine matics of the SARJ mechanism coupled with very high friction coef ficients pulled subsurface stresses up into the nitride laye r, resulting in nitride layer fractures and loss of the nitrided surface.
Failure Analysis of Gas-Nitrided 15-5PH Steel
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 20
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Carbon Tape Adhesion
Post-Test
Failure Analysis of Gas-Nitrided 15-5PH Steel
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 21
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
SE SARJ TBA Tape Pull Specimen Analysis
TBA 1045, Datum A, Test #2, Carbon Tape
• Gold coating was easily removed from trundle bearing roller surfaces using carbon tape, and was generally segmented into strips of dimension consistent with the as-machined surface finish.
Failure Analysis of Gas-Nitrided 15-5PH Steel
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 22
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
BSE
BSE Prelim SARJ TBA Tape Pull Specimen Analysis
SE
SE
TBA 1005, Outer 45, Test #1, SEM
Iron Oxide (by
elemental analysis)
Failure Analysis of Gas-Nitrided 15-5PH Steel
Outer Surfaces
Inner Surfaces
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 23
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Failure Analysis of Gas-Nitrided 15-5PH Steel
� Freshly gold-plated 440C after 21 days of 95%RH at 125°F.
� Adhesion failure mode is consistent with that observed with trundle bearing rollers.
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 24
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
• Summary of Failure Analysis• The nitride surface of the SARJ race rings had unre cognized
subsurface flaws susceptible to fracture initiation .• The lubrication system selected in design was not r obust
enough to maintain friction control.• Once friction control was lost, subsurface loads mo ved up
into the interface of and within the nitride layer.• Spalling probably initiated at DIGS, generating part icles which
exacerbated the surface stresses, leading to spalli ng of the nitride layer in a short period of time.
• Weak magnetic forces in the microgravity environmen t held released particles within in the mechanism, leading to crushing of the larger “chip” particles into fines a nd eventual agglomeration of those fines.
Failure Analysis of Gas-Nitrided 15-5PH Steel
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 25
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
• What has happened to the SARJ mechanisms?• We decided to lubricate using a MoS 2 + PTFE filled vacuum-
stable grease.• We cleaned the damaged Starboard race ring using th e same
grease to help capture particulate.• We replaced all of the Starboard SARJ trundle beari ng
assemblies.• After several test runs of increasing duration plus analyses to
determine the structural viability of the damaged r ace ring, theStarboard SARJ returned to nominal operation early 2010.
– Performance is characterized as excellent.• We applied the same grease to the Port SARJ as soon as we
could, and believe that we saved it from the same e ventual failure mode.
Failure Analysis of Gas-Nitrided 15-5PH Steel
ASM Houston Failure Analysis Seminar J.L.Golden 03 April 2012 26
Engineering, Operations & Technology | Boeing Research & Technology
Copyright © 2009 Boeing. All rights reserved.
Materials & Fabrication Technology
Failure Analysis of Gas-Nitrided 15-5PH Steel
ISS 2010
EOT_RT_Sub_Template.ppt | 27Copyright © 2009 Boeing. All rights reserved.