1. Welding Grade P-91
and Other CSEF Alloys
(Creep Strength Enhanced Ferritic)
The Canadian Welding Association (CWA) is organizing a seminar on
welding grade P-91, P92 and other Chrome/Molly/Vanadium Alloys.
These material types perform well at elevated temperatures and,
as a result, have become more commonplace in power generation
applications and in specific applications in refining industries. Special
attention must be paid to materials selection and design aspects. The
design and selection of welding consumables, welding techniques
and pre and post-heating avoid issues such as cracking and even
catastrophic failures of components. This seminar will bring greater
awareness of what the issues are and provide some solutions on how
these challenges may be solved.
CWB Group
8260 Parkhill Drive
Milton ON L9R 5V7
Date: March 25, 2015
Time: 8:00 AM – 4:30 PM
Register at: www.cwa-acs.org/events

2. Grade 91 steel, also known as the modified 9Cr-1Mo-V steel, is widely used in
the nuclear and fossil fuel power generation industries, due to its high creep
strength and corrosion resistance. A detailed metallurgical microstructure
analysis has been conducted on the heat-affected zone (HAZ) of Grade 91 steel
pipe welds under three conditions: the as-welded (AW), after a typical post-
weld heat-treatment (PWHT, 760°C for 2 hours), and after creep testing (CT).
Creep property of the welds has been measured at 650 °C with a stress level of
70 MPa. A type IV creep failure of the weld is identified in the fine grain heat-
affected zone (FGHAZ) close to the inter-critical heat-affected zone (ICHAZ). The
grain growth and re-distribution of the M23C6 carbides after PWHT are observed
by electron back-scattered diffraction (EBSD). The majority of the identified
Cr-rich M23C6-type carbides distribute on the tempered martensite or ferrite
grain boundaries in FGHAZ. After creep testing, the shear deformation and
recrystallization of the ferrite grains in FGHAZ is observed in the creep-damaged
area.
Author biographies:
Yiyu (Jason) Wang is a PhD candidate and Dr. Leijun Li is a professor in the
Department of Chemical and Materials Engineering, University of Alberta. Their
research focuses on basic and applied research in microstructure characterization
and properties evaluation.
Dr. Li has supervised research students in fusion and solid-state welding, and
laser and plasma-enabled additive manufacturing technologies. Dr. Li serves as
Principal Reviewer for the Welding Journal and Key Reader for the Metallurgical
and Materials Transactions. He is a Fellow of the American Society of Materials
and a past chair of the Joining Critical Technologies Committee of ASM.
Microstructural Evolution
During Creep of Grade 91 Steel Pipe Weld
Leijun Li, Yiyu Wang
Department of Chemical and Materials Engineering
University of Alberta
Leijun Li
Yiyu Wang
2

3. 3
Procurement of standard, commodity type welding consumables is rather
straightforward. However, when weld metal toughness, properties after post weld
heat treatment, specified hardness, or other out-of-the-ordinary requirements are
needed, communication between the purchaser and supplier becomes critical. In
cases where the lowest bid rules, sole sourcing is difficult, or when merely stating
the AWS filler metal specification and classification is not adequate to obtain
exactly what is needed, frustration can result, deliveries delayed, or inadequate
products may be purchased. These factors are especially important where the creep
strength-enhanced ferritic steels such as Grade 91 are involved.
Over the last decade, it has become apparent that wire processing is critical to
success and defect free welding, especially where automated or orbital gas tungsten
arc welding (GTAW) is used. The composition of many alloys, especially the creep
strength-enhanced ferritic weld metals are lean on deoxidizing elements because of
their detrimental effect on elevated temperature creep strength. Aluminum, silicon,
titanium and manganese are traditionally used to deoxidize or “clean” the molten
weld pool and assist the escape of gases, thus reducing or eliminating porosity.
Any foreign material on or in the wire can jeopardize the cleanliness of the weld.
Manual GTAW typically can tolerate more contaminants because the weld pool is
somewhat more turbulent and assists the evolution of gases or other contaminants.
Remedies and practical examples will be discussed.
Author Biography:
Bill Newell is involved in welding engineering applications and consulting in the
nuclear and fossil electric power and heavy industrial arenas for over 40 years, both
domestic and internationally. Bill graduated from The Ohio State University with
a B.S. in Welding Engineering and was also awarded a diploma as an International
Welding Engineer by the International Institute of Welding. He holds Professional
Engineer licenses in Ohio, North Carolina, South Carolina, Tennessee and Texas, plus
Alberta, Canada and holds four patents on welding related technology.
Bill is a member on national and international code bodies, a Life Member of the
American Welding Society, and a member of AWS A5N, Vice Chair of AWS D10 and
Chairman of D10C and D10I; a Member on ISO/TC 44, International Committee on
Welding and Allied Processes, plus a member of ASME Standards Committee IX –
Welding and Brazing Qualifications, ASME Post Construction Issues – Subcommittee
on Materials and Repair, Chair of ASME SCII/IX Subgroup on Strength of Weldments,
and a member on the ASME SCII Task Group on Creep
Strength-Enhanced Ferritic Steels. He is the President of W. F. Newell & Associates,
Inc., a consulting firm that specializes in welding engineering and Co-Founder/
Vice President – Engineering of Euroweld, Ltd., a supplier of specialty welding
consumables and technology.
Weld Metal Procurement for
Grade 91 Welding
Bill Newell, P. Eng.
Euroweld

4. 4
Loss of creep resistance in post-weld P91 alloy occurs mainly due to the change
in grain size as well as residual stress from the welding process. Post-weld heat
treatments can partially improve the creep life, however it remains important to
determine the remaining useful life (RUL) particularly in the heat-affected zone
under actual service operating conditions. Most creep damage models have focused
on the short term creep response at relatively high temperature and stress, where
the deformation mechanism is governed by power-law creep (PLC). However, under
the actual service temperature and stress (i.e. about half of the melting point) grain-
boundary sliding (GBS) is the dominant deformation mechanism that contributes
to the creep life. In this paper, a validated deformation mechanisms map (DMM)
using low temperature creep strain accommodation processes i.e. GBS, is developed
for P91 alloy that predicts the creep rates over a wide range of temperature and
stress including those arising under the actual service conditions. These creep rates
are further utilized in a microstructure-based creep damage model for accurate life
prediction. A 3D transient computational welding mechanics (CWM) modeling of a
pipe in a super-critical water loop, predicts the thermal, microstructure and stress
state from welding. It also determines the coarse and fine grain heat affected zone
(CGHAZ & FGHAZ). The CWM results are coupled with physics-based creep damage
modeling to predict the RUL under the actual service conditions considering the
welding residual stress and microstructure states.
Author Biography:
Mahyar Asadi received his engineering degree in Material Science and Engineering
(1999), and his Master’s degree in Material Science and Engineering, majoring in
Welding (2001). He started his career in the automotive industry’s inspection and
quality control including a promotion to manager of the engineering department.
He was working for many years in the automotive sector before returning to
academia (2007) for his PhD in Mechanical and Aerospace Engineering, specializing
in Computational Welding Mechanics supervised by the distinguished research
professor, Dr. John Goldak. After graduation (2011), he was granted a prestigious
Canadian NSERC-PDF award and started post-doctoral position working jointly at the
University of Ottawa and at the University of British Colombia in fracture mechanics,
creep and fatigue analysis in close collaboration with industry. Together with Dr.
John Goldak, he has developed and offers his signature course on welding models
and computational welding mechanics at the university graduate level. He is also
licensed by the Province of Ontario for practicing as a P. Eng.
A Coupled Computational Welding Mechanics and
Physics-Based Damage Modeling for Prediction of
Remaining Useful life in Welded P91 Alloy
Dr. Mahyar Asadi and Dr. Jun Zhao
Life Prediction Technologies Inc.
Leijun Li, Ph.D., FASM
University of Alberta

5. 5
Experts are suggesting that roughly 90% of material anomalies and premature weld failures in Grade 91 CSEF
steels can be attributed to improper Pre and Post Weld Heat Treatment. While the benefits of CSEF steels are
well documented and growing in popularity, welding processes and skill sets become more critical than on
steels with lower chrome content, and sensitivity to PWHT becomes more significant than ever before.
As an industry leader and innovator in Advanced Industrial Heat Treatment Services, Superheat FGH will
attempt to shed light on some of the pitfalls of traditional field service practices and shortcomings of existing
weld procedures, code guidelines and specifications that, in many cases, have been established with more
forgiving materials in mind.
Topics discussed will include significance of heat treatment in achieving material properties; practical methods
of heat treatment in use today; latitude given service providers through non-specific procedural guidelines;
insight to implementation pressures, and new technologies available to enhance Quality Control, Process
Quality Management and enhanced Oversight capabilities.
Influence of Pre and Post-Weld Heat
Treatment on CSEF Steels
Gary G. Lewis
Superheat FGH Mooresville

6. Creep strength-enhanced ferritic steels such as 9Cr-1Mo-0.25V grade is used
worldwide in power industries as well as petroleum refining and related industries.
Today’s combined-cycle power plants and advanced coal-fired plants operate at
more demanding operating conditions such as high super heater temperatures, and
undergo rigorous cycling (in some countries).
9Cr-1Mo-0.25V alloy, popularly known as Grade-91 steel, is extremely popular
amongst designers. Due to higher allowable design stress as well as higher creep
strength, such materials offer significant savings in material thicknesses for front-
end design of critical boiler tubing and thick-walled piping and other components.
Components with thinner wall produce substantially reduced thermal stresses while
cycling and thereby improve service life.
The lessons learned thus far with P(T)91 weldments have truly demonstrated that
this steel is quite different and requires significantly more detailed attention than
the P(T)22 and lesser grade low alloy steel materials used in the utility industry.
Grade 91 alloys require a very thorough design analysis, materials and welding
consumable selection, a very controlled welding and PWHT requirements to sustain
safely and reliably in service.
Grade -91 steel delivers the best mechanical and high temperature creep properties
when it’s fabricated with the utmost quality control. In the subsequent pages/
presentations the author has tried to develop a detailed roadmap for good welding
and fabrication practices for this alloy, for demanding and cyclic services in today’s
power industry.
Author’s Biography:
Pradip Goswami has over 30 years of versatile experience as a Welding and
Metallurgical Engineering Specialist in Power Generation, Oil Refining, Oil and Gas
Production, Petrochemical Industries. He has a strong Fundamentals in Welding,
Metallurgical Engineering with welding experiences in Cr-Mo-V steels (refinery
hydrocrackers), T-91/P-91 Steels, Duplex and Super Duplex Stainless Steels, Super
Austenitic Stainless Steels (254SMO). He has a number of publications related to the
above alloys in international conferences/journals.
The author is quite an active participant and respondent to technical queries in
various Professional internet forums, LinkedIn, Eng-Tips, Materials-Welding Group.
Modified 9Cr-1Mo-V (Grade-91) Steel, A
Comprehensive Review of Design and Fabrication
and Best Industry Practices.
Pradip Goswami, P. Eng., IWE Welding &
Metallurgical Specialist
6

7. The Electric Power Research Institute (EPRI) has been actively researching the integrity of alternative well-
engineered cold weld repair (i.e. no post weld heat treatment, PWHT) and low PWHT weld repair options for
Grade 91 steel components. This research has resulted in the incorporation of Welding Method 6 for tube to
tube weld repairs into the National Board Inspection Code (NBIC), Part 3 - Repairs and Alterations, proposal of
a new Welding Supplement to the NBIC, Part 3 - Repairs and Alterations. It has ignited recent discussion within
the American Society of Mechanical Engineers Boiler and Pressure Vessel (ASME B&PV) Code regarding the
relaxation of the current minimum allowable PWHT of 1350°F (730°C) to 1250°F (675°C) for new construction
of Grade 91 steel weldments. The value of alternative weld repair procedures will be detailed in the context of
destructive evaluation testing and application considerations which are discussed in a recently released EPRI
Report (3002003833) Best Practice Guideline for Well-Engineered Weld Repair of Grade 91 Steel.
Alternative Well-Engineered Weld Repair
Options for Grade 91 Steel
John A. Siefert and Jonathan D. Parker
Electric Power Research Institute (EPRI)
7

8. Registration: www.cwa-acs.org/events
Member: $425
Nonmember: $525
Student: $150
(lunch is included)
Seminar Cancellation Policy: The seminar registration fee, less 25% per
person, will be refunded if cancellation is made in writing on or before
March 12, 2015. There will be no refund for cancellation after this date.
CEU Credits: This seminar qualifies for .5 CEU’s.
Agenda:
8:00 – 9:00 Breakfast and Registrations
9:00 – 9:10 Opening remarks and Introductions
9:10 – 10:00 Yiyu (Jason) Wang and Dr. Leijun Li - Microstructural
Evolution During Creep of Grade 91 Steel Pipe Weld
10:00 - 10:20 Morning Break
10:20 – 11:10 Bill Newell - Weld Metal Procurement for
Grade 91 Welding
11:10 – 12:00 Pradip Goswami - Modified 9Cr-1Mo-V Steel, A
Comprehensive Review of Design and Fabrication and
Best Industry Practices
12:00 – 1:00 Lunch (included)
1:00 – 1:50 Gary Lewis - Influence of Pre and Post Weld Heat
Treatment on CSEF Steels
1:50 – 2:40 John A. Siefert - Alternative Well-Engineered Weld
Repair Options for Grade 91 Steel
2:40 – 3:00 Afternoon Break
3:00 – 3:50 Mahyar Asadi - A Coupled Computational Welding
Mechanics and Physics-Based Damage Modeling for
Prediction of Remaining Useful life in Welded P91 Alloy
3:50 – 4:20 Roundtable discussion with Presenters
4:20 – 4:30 Wrap up
Location:
CWB Group
8260 Parkhill Drive
Milton ON L9R 5V7
Date: March 25, 2015
Time: 8:00 AM – 4:30 PM
Should you require Hotel accommodations, please contact Holiday Inn
2750 High Point Dr. Milton, ON L9T 5G5 Telephone: (905) 876-4955
and request the preferred CWB Group rate of $115 per night. Taxes are
extra. The Holiday Inn is located a short 5 minute walk from the CWB
Group facility.