hardfacing circular, cold cracking

Date 09-08-2015 13:22

EUGENY,
Some things to try...

Base material must be very clean..

Fought this same issues many years ago. The surface cracks propagate am I correct.

Turn up the preheat and interpass to the 700 & 800 deg F. Slow cool under blanket or sand.

Try using Inconel as a butter layer and deposited Stellite 6 on top of this butter layer to reduce susceptibility to cracking, during and after hardfacing. Slightly increased preheat, and tight stringer beads to deposit Stellite 6 directly on top of low alloy steel.

Try Stellite 21. This is a lower hardness version of Stellite 6 and is more forgiving (less crack sensitive).

I would give 316L a try as well.

Good Luck

By Eugeny

Date 09-08-2015 14:49

JARHEAD1,
Thank you for your attention!

I also tend to increase preheating. Manufacturer of Stellite (Deloro) recommends preheating 100-150 Celsius.

To use another Stellite is not possible, because of the required high hardness.

Folloowing Stellite 6 Mmanufacturer recommendations, ASME B31.1 and ASME III requirements, it is not need to perform PWHT.

By welderbrent (*****)

Date 09-07-2015 13:25

It's the last holiday weekend of the summer. People are out enjoying their families and many other activities. Hold onto your hat and be patient.

BB

By electrode (***)

Date 09-08-2015 18:22

Regarding the photograph this may add value to your answer:

http://www.thefabricator.com/article/cuttingweldprep/frequently-asked-questions-about-hardfacing

By js55

Date 09-08-2015 19:04

Al is correct in that not only are cracks not uncommon in hardfacing, I will add that in many hardfacing applications the number of cracks is a variable used for procedure qualification. When I worked for a hardfacing company we would qualify procedures and mixes with a minimum and maximum number of cracks per linear constant.

By Eugeny

Date 09-09-2015 08:17

Al,

The manufacturer's recommendations were followed - preheating 150 Celcius and slow cooling in vermiculite.

In our case, the crack is not acceptable!!! Valves for nuclear power plants...

In our case the cracks of the main character. In different cases, either axial or radial.

Sorry for my English. Thank you all for your answers!

By Eugeny

Date 09-09-2015 07:53

Welderbrent,

thank you!

These are the details for valves in nuclear power plants. The cracks appeared to use the items, but after more than a few months!
Cracks are of two types - axial and radial. With different parts. Axial fully cross the surfacing. Radial 2/3 of the diameter.

Still not clear who is to blame. The manufacturer says that everything was well made and the technology meets the standards. The customer says that marriage is the production.

The manufacturer says that the repair is not possible.

By CWI555

Date 09-09-2015 16:10

One of the things that fell out of the TMI incident (three mile island) was the cobalt reduction programs.
The USNRC in conjunction with EPRI performed a multitude of test towards that end. They continue to do so for legacy issues.
The reason for the push is due to hardfacing and alloy 600 cracking leaving chunks of material in the primary systems of PWR reactor, an BWR reactors (from the stellite in the turbine system for those). That material would get activated forming Co58, and for the nickel, Co60 among other isotopes. That made the plants 'hot'. It was a particular problem for clean up of TMI as the workers were getting nailed by those Hotspots where they shouldn't have been getting any dose.

EPRI has a large data base on the subject.
That's what I recall from memory. What your dealing with is not an unknown to them. Suggest contacting them and or research along those lines.

By 803056

Date 09-09-2015 21:05

I was involved with applying a hardfacing material (Stellite) to some valve seats many years ago. I remember the preheat, welding parameters, and travel speed were very closely controlled. The travel speed for each layer in production was timed so the travel speed was within +/- 13 mm/minute.

It was too long ago to remember much more other than the valve material was equivalent to a 4130 and the preheat was around 600 degrees F.

Al

By welderbrent (*****)

Date 09-09-2015 23:42

Based upon now knowing more about your application, your pre-heat and inter-pass temps are probably not stringent enough. This is somewhat out of my league but with all I do know about hard facing you need to listen to Al and CWI and a couple of the others here.

While 150°C may meet manufacturer's specifications it more than likely will not suffice for your application.

During a recent incidence at the job I am inspecting as a TPI I have discovered how important metallurgy as a science can be for investigations of problems. But it takes having the right people and doing due diligence to check everything out. Metallurgy is a good forensic science to find out what went wrong and how to keep it from happening again.

He Is In Control, Have a Great Day, Brent

By Eugeny

Date 09-10-2015 07:38 Edited 09-10-2015 07:47

I completely agree with you, Brent, and with the other participants of the conversation. But I want to get more information and confirmed by any document. I have to argue their position.

Brief: to raise the temperature of preheating and inter-pass heating;
to reduce the thickness of surfacing;
+ may be PWHT.

I forgot to specify - GTAW. Can it's important.

Another point! The manufacturer claims that could crack due to mechanical processing. And the Truth was treated with only one detail.

Thank you all and have a nice day!

By Superflux (****)

Date 09-10-2015 20:09 Edited 09-10-2015 20:22

1) Is the "Soak Time" sufficient to allow the preheat to penetrate the core?
2) Is the 309 sublayer thick enough to minimize dilution of the Stellite with the core material?
a. Or.... Perhaps a more malleable sublayer or hardfacing alloy should be considered.
3) Could the homogeneity or integrity of the core material be a factor? Perform an Immersion UT scan for voids and density anomalies
4) Hard facing X's cycle rate = Cracking. It's kinda like a primary law in the universe.

By Eugeny

Date 09-10-2015 20:21 Edited 09-10-2015 20:46

Superflux,

1) I think Yes
2)after the deposition of the sublayer it is mechanically processed to a thickness of 1.5 mm. Сan't know for sure. Did not me. Says so WPS.
3)an ultrasound? No, it did not on surfacing.

By Superflux (****)

Date 09-10-2015 20:24

Please see revised posting.
The original #3 was an attempt at humor that was lost in the language barrier.

By Eugeny

Date 09-10-2015 20:44

Edited. On the blanks was input control on the ultrasound.

By welderbrent (*****)

Date 09-10-2015 23:11

The soak time is definitely an item that gets overlooked way too often. Just because the material is 'warm enough' on the surface does not mean it is all the way through. That is why you should generally heat from the side opposite where the welding will be performed and check the heat from that side as well.

BUT, when you do that you want to watch your material temp on the side where the heat is being applied because it is possible to get it too hot and cause as many problems from the over heated side as from the under heated other side.

Low temp heaters as in propane furnace racks, induction heating pads attached to the member, and other processes that will warm your parts in the through thickness without over heating any of it and then blankets and heating that will maintain your temp the entire time work is being done will help tremendously.

Just my two tin pennies worth.

He Is In Control, Have a Great Day, Brent

By Eugeny

Date 09-11-2015 10:15

Brent,

you are right! The manufacturer swears that all did!

Also let me remind you that the detail is small and thin, it's easy to heat, and cool easy...

And the main thing is cracked in a few months!!!!

Can't find good literature on such surfacings - Hardfacing.

By electrode (***)

Date 09-11-2015 10:44

Sir,

No offence intended and despite the high quality answers already provided here.
Due to the issue's complexity I suspect that these are just scratching the surface.

Maybe you can reveal something more tangible here: http://worldwidescience.org/topicpages/w/weld+cladding+overlay.html.

By Eugeny

Date 09-11-2015 11:45

writes that is not found :confused:

By Superflux (****)

Date 09-11-2015 11:07

I was hoping our member PhilThomas would chime in as he works for Stoody which is a world renowned hardfacing filler metal manufacturer. Perhaps by using Stoody in this post, it will alert his attention. If this does not get his attention, it might be to your benefit to message him directly and solicit his advice.

By Eugeny

Date 09-11-2015 11:57

Thanks for the tip. Wrote him.

By PhilThomas (**)

Date 09-12-2015 02:20

Sorry - I haven't logged in for a few days. I have a few questions and comments to see if I can assist you.

1. Is it correct that the cracking doesn't happen for several days/hours after the weldment cools to room temperature?

2. I can't tell from the photos - does the cracking occur ONLY in the Co 6 weld? Or is it extending into the 309L butter layer or the base metal?

3. How many layers of Co 6 are you depositing on top of the 309L?

This type of hardfacing (cobalt 6 valve overlays) should be crack free. Those who were referring to hardfacing that is expected to crack are likely thinking of a Cr carbide type deposit which (because of the 45-60+ HRC level) are supposed to have "cross checking". This is not what the photos show.

What is the process and rod type? If you are using the GTAW process you should be using the Co 6H rod whereas if you are using OFW you will want to use Co 6 due to carbon pickup from the flame.

By Eugeny

Date 09-12-2015 22:56 Edited 09-12-2015 23:00

Hello, Phil!

1. The first cracks appeared after 5 months on two parts. Then within months cracks appeared on the other six parts.

2. Can't say for sure. While no decision and no parts are not touching.

The manufacturing plant during the execution of mechanical pre-processing collided with cracks. They attributed this to the influence of vibration on thin cylinder walls. It was about a cracked cladding, not of base metal. Surfacing was repaired, and further mechanical processing was carried out in a snap eliminating the vibration. (The cracks were axial)

3. One layer the 309L =3mm, then machining to 1.5 mm. Then surfacing Cobalt 4 layers with a total thickness of 9mm, then machining to 6mm.

Process GTAW. Rod type ER CoCr-A (Deloro). Hardfacing E306L and Stellite-6 on SA266 gr.2 by SMAW-GTAW-manual - it is written in WPS.

Thank you for your attention.

By PhilThomas (**)

Date 09-28-2015 15:14

Eugeny - 1.5 mm of overlay is very thin to use as a substrate for the Co overlay. I suspect you are still getting dilution from the base material into the Co.

It also sounds as if there were cracks in the surfacing which were subsequently repaired before the valve went into service - is that correct? Such repairs must also be done quite carefully as it is easy to grind through the 309 overlay into the base metal.

It will be nearly impossible to resolve this cracking problem on the forum. There are so many variables that could be causing (either directly or in combination) - many have been suggested here.

By Eugeny

Date 09-28-2015 16:00

PhilThomas

Yes, it is claimed that the cracks appeared during machining due to vibration of a thin cylinder walls.

Do I understand correctly that if you follow the technology, that cracks should not have been born? That is the fault of the manufacturer?

Well, what do you say the thickness of the layer of Cobalt? Is it possible to use such a thick layer?

And another question - will decrease the mechanical properties of the cladding after heat treatment (t650c) processing or not?

Exactly the same details previously done by another manufacturer and they are doing well, the product for a long time and works well. The difference in technology was only in the heat treatment after welding.

By ssbn727 (*****)

Date 09-12-2015 03:57 Edited 09-12-2015 05:12

Whoops!I almost double posted... Ummm, I also couldn't help myself to post this link as a potential networking link for NRC/EPRI Welding and Repair Technology Center Overview... There is a page in this .pdf which has listed contact information to get in touch with this team of nuclear welding experts... The page is 11 of 48.

http://pbadupws.nrc.gov/docs/ML1116/ML11167A252.pdf

Respectfully,
Henry

By welderbrent (*****)

Date 09-12-2015 04:06

Amen. Just don't over do yourself Henry. I'm sure there is still some recuperation time needed.

He Is In Control, Have a Great Day, Brent

By ssbn727 (*****)

Date 09-12-2015 04:43

Hi Eugeny!

Here are some links to possible documentation to back you up in order to justify your suggestions to your management of the welding preheat, and PWHT or not when hardfacing stellite 6 to (what is the CE for the grade of steel being hardfaced?) steel:

http://www.stellite.co.uk/Portals/0/Guidelines%20for%20hardfacing%20onto%20steels.pdf

For this link, scroll down the .pdf to page 37 of 59:

http://c.ymcdn.com/sites/www.vma.org/resource/resmgr/2012_technical_seminar_&_exhibition/dr._danie_de_wet.pdf

Here's an interesting thread in the Engineering Tips forum that sort of mirror some of the comments found in this thread:

You might want to check and see the amount of Manganese in the steel in order to make sure that you either need to increase your pre heat, or if it requires PWHT, or both. Here are some more links to hopefully more helpful information and suggestions...
This link will lead you to another .pdf to download from it which explains the scope of the research that was performed on the Cracking and Disbonding of Hardfacing Alloys in Combined-Cycle Plant Valves... Although this doesn't directly pertain to nuclear components as is your application, The EPRI Customer service and technical resources contact information for their findings from this investigation:

http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000000001025658

Here is a similar paper as the one above and below... However the information is limited to 7FA class steam turbines Combine Cycle plants:

http://globalfield.net/pages/documents/2.pdf

Although this paper mainly talks abut SMAW electrodes as opposed to GTAW which you are using, and Combine-Cycle Plant valves as opposed to the Nuclear versions of these type of valves... There is a table # 2 which shows pre-heat temps dependent on the current (amperage) amount being applied... This table is located in page 2 of 6 in the .pdf below... I believe this is good starting point to go by as well as it being published in the May of 1992 edition of the AWS Welding Journal below...
"Cracking and Disbonding of Hardfacing Alloys in Combined-Cycle Plant Valves":

https://app.aws.org/wj/supplement/WJ_1992_05_s195.pdf

This one may or may not be of interest to you but, there may be something you can take away from this study:

https://www.iaea.org/NuclearPower/Downloadable/Meetings/2013/2013-03-04-03-07-CF-NPTD/T4.4/T4.4.marlaud.pdf

And finally this article in "Valve Magazine" covering valve repairs similar to your application except for the fact that these are not used in a nuclear power plant:

http://www.valvemagazine.com/index.php/web-only/categories/technical-topics/5144-in-line-weld-repairs-of-valve-defects

And this eye opener:

http://www.ans.org/pubs/journals/nt/a_33563

Well, that enough for me today... I'm tired and need to sleep for tomorrow... I will be discharged too, I'm coming HOME!!!

Respectfully,
Henry

By Eugeny

Date 09-12-2015 23:15

Hello Henry!

Many thanks for the info, will definitely learn.