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PWL#090 & 090B - Wear Resistant Coatings, Grinding root pass, Inconel 625 Overlay, Weld Bevels
February 01, 2011
We hope you will find this Letter interesting and useful.
Let us know what you think of it.

Wear Resistant Coatings, Grinding the root pass of welded pipes, Inconel 625 Overlay on Steel Castings, Weld Preheating, Heat Treating of Steels, Weld Bevel Angle of Preparation for Pipe Welding, Again on Welding Examination, and much more...

February 2011 - Practical Welding Letter - Issue No. 90


Mid February Bulletin

DON'T USE REPLY to send us your messages! Use Contact Us instead.

Please be advised that the Mid Month Bulletin is now integral with the regular PWL publication. You will find it further down, past the end of this Practical Welding Letter.
Don't miss it!

Important Announcement

For assembling at no cost your own Encyclopedia Online,
a rich collection of valuable information from expert Internet Sources, on
Materials, Volume 1,
and Metals Welding, Volume 2.
Order Now! at Metals-Knowledge.


1 - Introduction

2 - Article - Wear Resistant Coatings

3 - How to do it well: Grinding the root pass of welded pipes

4 - Filler Metals: Inconel 625 Overlay on Steel Castings

5 - Online Press: recent Welding related Articles

6 - Terms and Definitions Reminder

7 - Article - Forgeability and Welding

8 - Site Updating: Weld Preheating, Heat Treating

9 - Short Items

10 - Explorations: beyond the Welder

11 - Contributions: Weld Bevel Angle of Preparation for Pipe Welding

12 - Testimonials

13 - Correspondence: a few Comments

14 - Bulletin Board

(Sponsored Links)

1 - Introduction

Hello everybody! This 90th issue (quite a bit, I would say...) of Practical Welding Letter, opens hereafter with a few comments on how to tackle the complex problem of selecting both the material and the processing method for performing successful hardcoating overlay on all sort of implements.

Although much experience is available with users and suppliers, no practical procedure is found for doing so, based on fundamental knowledge. Therefore, short of performing full scale tests on a few different proposals, the best resort is to ask a knowledgeable expert or company, by supplying the maximum of data available upon the implement and its service conditions.

Then a reminder is proposed for those welding pipelines. Is there a preferred procedure for grinding successfully the root pass before completing the weld? There is, when accessible.

The question of a puzzled reader about a specific customer request presents the occasion for explaining which is the reason for such a special process and why it is not changeable without customer's consent.

How forgeability influences welding is the subject of the next article: it may be an item to check in case of difficulties with certain welding processes and materials.

The additions to the website this month are related to heat treatments: as the devil is in the details, it may be useful to know where to look for, in case of problems.

Bevel angle preparation is probably a routine choice. A kind reader presents some of the discussions that were involved in the past in prescribing the correct preparation of joints for pipe welding. A different proposal is reported from a renowned expert. Readers may wish to comment and to contribute.

The rest of the page flows normally along the usual sections that can be readily found at their regular place. Enjoy your reading and let us have your feedback and comments using the Contact Us Form.

The references to online resources, assembled in this issue for the Mid Month Bulletin, that follows the regular issue, are devoted to Hardfacing Research and related issues as a further addition to the items discussed in the article of the following section 2.

2 - Article - Wear Resistant Coatings

When considering Hardfacing for applying layers of wear resistant materials on any new of repairable implement, one has to take into the account the application, the base material, the application method, the wear resistant coating material to be applied, the cost and the anticipated time of useful service.

Of these factors the application itself, that is the extreme abrasive-erosive wear conditions actually existing or anticipated, are difficult to figure out with any precision. However, it is most important that the inquirers be able to communicate to suppliers of materials or of engineered solutions the actual conditions the implements involved will meet in their useful work life.

Generally one can only evaluate approximately the wear factors, namely the high hardness and strength of abrasives and materials to be processed, their high speed and pressure, impact cyclic loading and high temperatures.

But even if those characteristics are known with acceptable precision, one can only guess the kind of solution likely to provide acceptable results, because the performance is still dependent on the specific wear resistant material selected and on the application process, which both introduce unpredictable and unknown variables.

Tribology is the study, through application of scientific and engineering principles, of the outcome of contact interaction of materials in relative motion. While such studies are important to clarify the basic issues, practical decisions are still far from being readily obtained.

The tentative character of these studies are evident from the fact that there is no specific accepted standard for testing or measuring a material wear resistance. This is due to the complex nature of wear, and to the uncertain ways available to simulate wear processes.

The wear tests that have been developed for specific applications give only comparative indications on wear results in very defined conditions. In general laboratory tests can contribute some deep understanding but cannot supply real world solutions.

During the last few decades, various high velocity spray processes were developed with particle speed beyond 300 m/s. The high velocity oxyfuel (HVOF) thermal spray technology and the detonation spraying technology demonstrated remarkable improvement in the quality and properties of tungsten carbide-cobalt coatings.

The study of erosive wear resistance of different thermal sprayed coatings has advanced the requirements and the specification of materials and processes, limiting porosity, structure and hardness of coatings to improve wear resistance under impact erosion coatings.

Abrasive erosion wear for specific applications can probably be addressed with more than one solution. Experience with similar situations is probably the most important ingredient that should be sought with developers of materials, or with suppliers of finished coatings.

If different solutions seem feasible but it is unknown which one is to be preferred, and if the working conditions are reasonably constant, there may be some incentive in trying to rate them by assembling at least three of the different proposed coatings in the same setup so that all will be subject to the same working conditions for a certain time.

Visual evaluation of the worn conditions will suggest which is the most successful and the most cost effective. Partnering with trusted professionals of renowned Companies with demonstrated long time history of having provided suitable fixes to tricky situations is probably the best decision for whoever has no sufficient experience within the difficult field of Wear Resistant Coatings.

3 - How to do it well: Grinding the root pass of welded pipes.

The welding of the root pass of pipe joints is most critical for the success of the operation. The weld bead surface has to be ground, before welding upon it the fill passes. For assuring the maximum ease of the grinding operation and the best control of the ground surface, it is imperative that this operation be performed from the outside of the pipes.

This means that the root pass should be welded from the inside for all diameters that leave sufficient space for unhindered welding to the welder and his/her equipment. Obviously this is not possible for small pipes, where other means, like consumable inserts, may be required.

4 - Filler Metals: Inconel 625 Overlay on Steel Castings

Question: We have been asked to quote on producing [steel] castings which have a GTAW-P Hot Wire Process using ERNiCrMo-3 (Inconel 625) inlay on the flanges. Please explain this requirement. It also calls out "Process: GTAW-P Automatic." Can I substitute our traditional TIG process for this or is a machine required?

Answer: Only the customer could change the requirements. As a consultant I can offer my interpretation of the case. The requirement is intended to assure the minimum of steel dilution in the nickel alloy by employing a process with limited and controlled heat input. Therefore I would not think the process could be changed.

Useful information can be found in a publication on Joining (52 pages) at

At page 16 one reads: "For best results, iron dilution must be kept at minimum levels. Excessive amounts of iron in the overlay compromise the corrosion resistance of the overlay and can cause weld cracking".

On the GTAW-P process see my page

On Tig Hot wire see:

See also: Robotic Tig Welding at

5 - Online Press: recent Welding related Articles and Video

Tig Welding Pipe 6g Certification Test Techniques

Tandem MIG - High-Speed and High-Deposition Welding (16 pages)
Tandem MIG.

OSHA Issues $229,000 in Fines in Double Fatality

How metal production affects the welding process

Magnetic Pulse Welding of Dissimilar Materials: Part One
Key to Metals.

6 - Terms and Definitions Reminder

Air Feed is a thermal spraying process variation, where an air stream carries the powdered surfacing material through the gun and into the heat source.

Bond Line is the cross section of the interface between thermal spray deposit and substrate.

Cutting Electrode is a nonfiller electrode made of carbon or metal, used in arc cutting.

Diffusion Welding is a solid state welding process that produces a weld by application of pressure at elevated temperature, with no macroscopic deformation, melting or relative motion of the workpieces. A solid filler metal may or may not be inserted between the faying surfaces.

Electron Beam Cutting is a thermal cutting process that uses the concentrated energy from a beam of high speed electrons impinging on the workpiece, with or without the use of an external gas.

Mash-Seam Welding is a resistance seam welding process variation that makes a lap joint by high temperature plastic working and diffusion as opposed to melting and solidification. The joint thickness after welding is less than the sum of the original thickness of the two elements.

Root Edge appears when the root face is zero or when the bevel reaches the back side of the plate.

Shielded Metal Arc Welding (SMAW) (also called Stick welding) is an arc welding process where the arc occurs between a covered electrode and the workpiece. Filler metal is provided by the melting of the metallic core, and Shielding is provided by decomposition products of the heated covering.

7 - Article - Forgeability and Welding

What has Forgeability to do with Welding? Well, in certain operations, it may be determinant to welding success. The term Forgeability was briefly introduced recently (Click on PWL#086 to see it in section 9.1).

Forgeability, used interchangeably with Workability, refers to the relative ease by which materials are shaped by bulk forming without failure. The first term refers generally to forming operations performed at elevated temperature where the material flow is easier, while the second refers also to deformations done at room temperature.

It is not surprising that welding processes relying on substantial material deformation in order to be accomplished, will depend on forgeability in a certain measure. Absence of cracks is the only requirement in this limited definition of success of a welding operation.

In general, welding processes relying on pressure or on blows in order to be performed, will depend heavily on the behavior of materials under conditions conducive to plastic deformation. If this cannot be performed without cracks because of low forgeability, then also the welding processes will not be accomplishable without cracks.

First among them is obviously Forge Welding, but also Resistance Welding Processes, Flash Welding Process and Upset Welding. These welding processes where substantial pressure is applied will not succeed on, say, cast iron which is not forgeable.

The same situation will be prevalent in Hot Pressure Welding and in High Frequency Resistance Welding, but problems should be considered also in Friction Welding Processes where cracks from the weld flash may penetrate the welded joint.

Some of the cold welding processes are based on plastic deformation. Ultrasonic Welding, Magnetic Pulse Welding and as such depend on material formability or workability.

The list of the welding processes being hindered by low materials ductility may be incomplete, but the general concept to be retained here is that, if a welding process results in the appearance of cracks because of applied force or pressure, the probable reason may be found in the limited material forgeability.

8 - Site Updating: Weld Preheating, Heat Treating

The Pages added this Month to our website deal both with Thermal Treatments. The first, connected with welding operations, explains the reasons for preheating, a precaution often required that contributes to the welding success.

The page is available by clicking on Weld Preheating. It refers also to the need to avoid the appearance of cracks during or after welding from a range of causes, mainly hard microstructure and hydrogen embrittlement.

The second page, more general in character, introduces an overview of the main Heat Treatments used for bringing various steels to exhibiting the mechanical properties most suitable to the prevailing service conditions of each application. It is found at Heat Treating.

Generally the updates are announced in our Welding Blog also available at a service to which any reader may subscribe to stay updated. See instructions below the Navigation Bar at the top left of each page from our website.

Updates can also be found in our pages Site Map and Index Page built to let readers find easily what they may be looking for. Except that these days the Site Map is undergoing a major revision because of a few errors that were remarked. It should be up again in a few more days.

You are urged to inform your friends of this website: they may benefit from the quite extensive information available to all readers and can ask questions that may help them.
Let us have your comments on the form of the Contact Us page.

9 - Short Items

9.1 - Nitriding is a case hardening process consisting in introducing nitrogen into the surface layer of a solid ferrous alloy, by holding it at a suitable temperature in contact with a nitrogenous material, usually ammonia gas or molten cyanide of appropriate composition. Quenching is not required to produce a hard case.

9.2 - Punching is the die shearing of a closed contour in which the shape of the hole is controlled by the shape of the punch and its mating die. The sheared out sheet metal part is scrap.

9.3 - Riser is a reservoir of molten metal, part of the mold and connected to a casting, to provide the additional metal required to fill the casting, as the result of shrinkage before and during solidification.

9.4 - Superheating is a metastable state obtained by heating slowly a substance above the temperature at which a change of state would ordinarily take place, without the change occurring. Or any increment of temperature above the melting point of a metal, introduced for the purpose of refining, alloying, or improving fluidity.

9.5 - Transition Temperature lies within the temperature range in which metal fracture characteristics change rapidly, such as in the ductile-to-brittle transition temperature (DBTT) and is variously defined. The the most common is the temperature for 50% ductile and 50% brittle fracture, or otherwise the lowest temperature at which the fracture is 100% ductile.

9.6 - Warpage is the Deformation other than contraction that develops in a casting between solidification and room temperature or the distortion that occurs after welding and during annealing, stress relieving, and high-temperature service.

10 - Explorations: beyond the Welder

Buckyball Tricks [Video]
ASM International.

The Future of Urban Transportation [Video]

Gadget Guide [Slide Show]

Middle Eastern Stone Age Tools

Arctic current warmer

11 - Contributions: Weld Bevel Angle of Preparation for Piping.

I am grateful to the reader
Jeff L. Stasney
J.and J. Enterprizes
who kindly submitted the following contribution.

There was an argument prevalent, back in the day, concerning weld bevel angle of preparation for piping.

The argument was API insisted a piping bevel preparation angle to be a 30 degree angle from perpendicular for a "Standard" bevel preparation angle.

ASME insisted a piping bevel preparation angle to be a 45 degree angle from perpendicular for a "Standard" bevel preparation angle.

Enter AWS/ANSI to settle the argument with a compromise of splitting the difference of API's 30 degree bevel and ASME's 45 degree bevel from perpendicular with 37 1/2 degree bevels from perpendicular as a "standard" by which piping bevels would adhere to.

Some would have this to be folklore other than fact. Opinions vary.

Ed Craig of, in his book "A Management & Engineering Guide to Mig Welding" explains that there is more than the bevel angle (that is actual welding parameters) for the success of the operation. In any case Ed suggests at page 478 of his book that 80 deg (total bevel) is preferable to 60 deg for Mig welds on rotated pipes, and he explains why.

"Note: The 80 degree bevel is beneficial for Mig Welds on rotated pipe because it allows for a longer weave dwell time, improved gun angle space, and a thinner weld bead. The 80 degree bevel with the thinner wall will also provide more localized heat from the weld, or from the additional weld passes required. The increased heat adds to the weld fusion potential".

12 - Testimonials

12.1 - Date: 11 Jan 2011, 10:51:21 AM
Name: Larry Mastin
E-mail Address: removed for security
Country: United States
Sales Manager
Questions and Feedback : Trying to determine [...]

Please advise asap.

Thanks very much.

Date: 01 Jan 2011, 07:11:00 AM
Name: Robert Li
E-mail Address: removed for security
Country: Indonesia

[...] thank you

13 - Correspondence: a few Comments

13.1 - A kind reader, Anthony Rangus, Principal Engineer, Bechtel Oil, Gas & Chemicals
took exception to my definition appearing in the last issue of PWL.

"Visual Inspection procedures establish which characteristics must be examined before, during and after welding to avoid unacceptable features and to assure conformance to requirements."

Here is his comment:
"Be aware the ASME B31.3 Code treats "Inspection" activities & "Examinations" as two separate & distinct functions.
Examination is used to look at characteristics to determine acceptability to a defined set of specific attributes.
Inspection activities are reserved to the Owners Inspector to assure overall Code compliance."

I took again on the issue and I checked with the following Source.
The AWS Welding Handbook, Ninth Edition, Vol.1, page 580, lists the following definitions:
"Examination - An activity that results in the indirect measurement or determination of the quality of a material or component. Examination can be performed without causing the destruction of the test object;
Evaluation - The consideration of examination and test results to determine the suitability of a component in terms of its quality or performance;
Testing - an activity that results in the direct measurement or determination of the suitability of a material or component for a prescribed service. Since a test involves the application of an actual or simulated service condition, the test object may be destroyed as a result of the process; and
Inspection - The overall quality control and assurance activity that encompasses other elements, including examination, testing and evaluation."

From the above it follows that (page 584) "Visual Examination (VT) is the nondestructive examination method that is used most extensively for weldments.[...]"

However (page 587) "For optimal results the visual inspection activity must occur at various stages in the fabrication process - prior to the initiation of welding, during welding, and subsequent to the completion of welding operations".[...]

It is true that confusion should be avoided, and I am grateful to Anthony Rangus that "takes great pains to use the terms correctly in the context of [...] Codes and Standards."

13.2 - Another reader, Wendy Potter, sent a comment on the subject discussed here above. "Conducting a visual assessment is always important when you are conducting a welding project, to monitor for safety and effectiveness". I am sure this meets universal agreement.

13.3 - Another reader, Chris Gardner, Process Engineer took exception at what I wrote in the Welding of Plastics page.
"You say that welding thermosetting resins is not possible. We weld cured (sintered) thermosetting resins all the time and can achieve near parent material physical properties at the weld joint.[...]

I asked for details and references, but unfortunately I got none.

From some search I found the following:
Thermoset can be rigid or flexible. It cannot be melted with heat.
The one exception to this rule is Polyurethane (PU, PUR). Thermoset urethanes can be easily repaired with the airless plastic welder. This will not give you a true fusion weld but the repair will be more like a brazing process.

Readers with more experience on this subject are invited to contribute their knowledge.

14 - Bulletin Board

14.1 - LAM - Laser Additive Mfg. Workshop, 3rd Annual
Feb 16, 17 - Sheraton North Houston Hotel, Houston, Texas

14.2 - Underwater Intervention 2011
Feb 22-24 - Ernest N. Morial Convention Center, New Orleans, La.

14.3 - Follow SiteSell to discover new avenues.

SiteSell Facebook

SiteSell Twitter

On SiteSell Twitter, visitors will learn who SiteSell is, through each person delivering personal insights into SiteSell... his news, his interests and perspectives. They can interact with each "SiteSeller" too, asking questions of programmers, coaches or anyone else.

SiteSell YouTube

SiteSell Blog

Case Studies


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Please continue to browse down hereafter for the Mid February Bulletin.

Copyright (©) 2011, by Elia E. Levi and
All Rights Reserved

* * *

Bulletin 58 - PWL#090B
February 2011

keywords: Hardfacing Research, Laser Cladding, WC Hardfacing, PTA Hardfacing, Microstructure

PWL#090B - Resources on Hardfacing Research, Laser Cladding, NOREMTM, Hardfacing Processes and Materials, Tungsten/Carbides (WC) Hardfacing, Plasma Transferred Arc (PTA) Hardfacing, Microstructure, Parameters Control, Abrasive Wear, Hard Stuff, Commercial Companies Listing and much more...

Mid February Bulletin

February 2011 - Resources on Hardfacing - Bulletin 58

Important Announcement

For assembling at no cost your own Encyclopedia Online,
a rich collection of valuable information from expert Internet Sources, on
Materials, Volume 1,
and Metals Welding, Volume 2.
Order Now! at Metals-Knowledge


This Mid February Bulletin # 58 is now integral with and appended to the regular PWL#090 publication.

The subject of this Bulletin is a collection of Online Resources on Hardfacing as an addition to the Article published in Section 2 above, on Wear Resistant Coatings. Here some information is presented from authoritative sources on different aspects of Research.

An older Mid Month Bulletin already provided some interesting information presented by different suppliers on the same subject. Click on PWL#036B to see the old Bulletin #4 of Mid August 2006.

We add also the reference to some of the suppliers of materials, equipment and services, not intending any recommendations but rather as a source of further knowledge that may be useful to solve practical problems.

We urge our readers to Bookmark this page and to subscribe to our Welding Site Blog by clicking on the orange buttons under the NavBar in each Website page. (
You may also click periodically on the Welding Blog button in the NavBar.

The addresses reported hereafter were live and correct at the time of their publication. There is no guarantee that they will always be so, because they are administered by the sources themselves and are under their control.

Note: References to articles or other documents are given here in
one of two forms. If the links are "live" (usually underlined or otherwise highlighted) they are operated with a click of the mouse.

If they are URL's (Uniform Resource Locator), which is the analogue of an address, they begin with "http://..." or "www.". These are not live and must be copied and pasted entirely into the browser (after having selected them with the mouse or otherwise). If they are long they may be displayed in two or more lines. In that case one has to care that the URL be copied completely in a single line without any space, and Enter.

If the information is important to you as we hope, you may save the selected pages in a suitable folder on your Computer for easy reference. You are welcome to forward this page to those of your friends who may profit of this information.

* * *


Hardfacing of aluminium alloys by means of metal matrix composites produced by laser surface alloying

Performance of NOREMTM Hardfacing Alloys (58 pages)

Laser Cladding of Nickel Based Hardfacing Materials as an Alternative of Stellite

Titles or Reviews of Searches on Weld Hardfacing Alloys

Titles or Reviews of Searches on Based Hardfacing Alloys

A Review Paper on Hardfacing Processes and Materials (4 pages)

Hardfacing of Petroleum Gate Valves (6 pages)

Tungsten – Carbides Hardfacing of the Drill – Stem Components

An Improved Wear-resistant PTA Hardfacing: VWC/Stellite 21 (Abstract)

Effects of Nb, V, and W on Microstructure and Abrasion Resistance of Fe-Cr-C Hardfacing Alloys

Understanding the Parameters Controlling Plasma Transferred Arc Hardfacing Using Response Surface Methodology (Abstract)
or, two first pages

Laser Cladding of Tungsten Carbide Hardfacing Alloys on Steels
Used in Mining Industry
(Abstract)(paper for sale)

Abrasive wear of high chromium Fe-Cr-C hardfacing alloys (7 pages)

Hardfacing of Conventional and Hollow-stem Augers -- Part 1

Hardfacing: Building Erosion-resistant Overlays – Part 2

Residual Stress Distribution in Hardfaced Austenitic Stainless Steel Sleeves (6 pages)

Evaluation of Overlay on Stainless Steel by NDE Methods (Abstract)

High Toughness High Hardness Iron Based PTAW Weld Materials
(15 pages)
Nano Steel Co..

Some Considerations of Wear and Hardfacing Materials

Development of hardfacing material in Fe-Cr-Nb-C system
for use under highly abrasive conditions

Development of Welding and Hardfacing Technology (17 pages)

Cavitation- and Erosion-Resistant Thermal Spray Coatings
(146 pages)

Iron-base wear-resistant alloys

Surface Hardening, Hardfacing, Hardsurfacing - What are the choices?

Mining Wear & Corrosion

Hardfacing Coatings for Wear and Corrosion Resistance Applications: Corrosion and Wear Protection I
MS&T Organization.

High-temperature cyclic impact abrasion testing
The Free Library.

Microstructure Change caused by (Cr,Fe)23C6 carbides in High Chromium Fe-Cr-C Hardfacing Alloys (5 pages)

Making the Hard Stuff

Commercial Companies


The links provided hereafter are reported as advertised in Search Engines, for the useful information they may add to interested readers. By presenting the links, I assume no responsibility as to their fitness to any usage or to specific solutions. No endorsement or recommendation are intended. No interest whatsoever connects me to these suppliers and no gain will come to me from any direct query to them. Readers should examine independently if the offers promoted there might help them in solving their specific problems.

List of Suppliers. Rock & Aggregate Marketplace

Technical Data Sheets - Technogenia

Plasma Transferred Arc Hardfacing

OTI - Hardfacing Types

Rockmount Nassau - Products

Hardfacing and Clad Plate

Deloro Stellite Equipment and Hardfacing Alloys

Hardfacing Guide (52 pages)

The best in hardfacing (15 pages)

Soudokay - Cored wires for Hardfacing

Technology enhances wear resistance

Innovative solutions in weld-cladding technology

London & Scandinavian Metallurgical Co Limited - Hardfacing/Coating

Laser Welding Solutions

Welding Wear Plates$4727

Cutting & Wear - Hardfacing & Engineering (6 pages)

* * *

Hardness Testing
made simple

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