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"Wear It's At"

Volume 2 Issue 6

Friday, November 3, 2000

"Happy Sandwich Day"

 

In This Issue

1. Welcome and Thanks
2. Virus Scare
3. Chromium (Complex) Carbides Part IV
4.  Future Topics
5.  November Is....


1. Welcome and Thanks


A hardy hello and a warm welcome to all our new subscribers.  I just want to let you know that any and all comments and contributions will be cordially accepted.  If you have an article or a topic you would like to share with others, please email or fax us and we will include it in one of our issues.


2. Virus Scare

Yesterday I was sent an email regarding a "California" email virus.  I have been attacked before by a virus and it is not pleasant trying to resurrect old files, etc. So when I received the friendly email, warning me of the virus, I immediately sent a well intended warning email to the participants in the Wear It's At newsletter.  A number of emails returned advising me that this virus was a HOAX.  I apologize for any inconvenience and any anxiety that I might have caused.  As one hoax informant said "But forewarned is better than not."  Thanks for the heads up.  If you would like to read about the virus hoax, plan to visit this web site:  http://www.symantec.com/avcenter/venc/data/wobbler-hoax.html . Despite the comment about me spreading rumors, I will continue to inform my friends, clients and associates whenever I suspect a virus, hoax or otherwise. "But forewarned is better than not."

3.  Chromium (Complex) Carbides Part IV 

Up to now we have been discussing Chromium Carbides.  In this edition, I would like to extend our discussion to Complex Chromium Carbides.  

What are Complex Chromium Carbides anyway?

If you will recall, I spoke at length in a previous newsletter, that Carbon is very fickle.  It likes to marry any number of suitors.  Carbon is polygamous.  Among the most popular suitors are: Iron, Chromium, Molybdenum, Columbium, Tungsten, Titanium, and Vanadium. While Chromium is probably the most popular and the least expensive element to form a Carbide, it does not have exclusivity.  In other words, any number of atoms of Chromium can be replaced in a Chromium Carbide with any one of the suitors.  This changes the Carbide characteristics and can sometimes increase wear resistance.  In addition to combining with the an existing Chromium atom in the Carbide, more importantly it will form its own Carbide.  For example, additions of Molybdenum to a Chromium Carbide Iron Base Alloy will form Molybdenum Carbide, a very hard and high temperature resistant Carbide. Because of its high hardness and high temperature qualities it contributes immensely to the abrasion resistance of a standard Chromium Carbide alloy.  Hence we have a COMPLEX CHROMIUM CARBIDE ALLOY.  Substituting the other suitors to the base Chromium Carbide alloy will have the same affect (more or less - depending upon the individual element added).  Of course it must be understood that a proportional amount of Carbon must also be added to the base alloy also.

How hard are Carbides????

The table below will help put this into perspective:

Type Carbide

Microhardness in Vickers (Approximate Values)
Iron Carbide (Fe3C) 1100
Chromium Carbide (Cr7C3) 1800
Molybdenum Carbide (Mo2C) 1800
Tungsten Carbide (WC) 2100
Tungsten Carbide (W2C) 2500
Columbium Carbide (CbC) 2400
Vanadium Carbide (VC) 2800
Titanium Carbide (TiC) 3200

Judging from the hardness of all the reported carbides above, one might ask why don't we use more Titanium in Chromium Carbide alloys or other alloys for that matter?  Well, the answer is quite simple.  Titanium also loves Oxygen and Nitrogen, almost as much as it does Carbon and therefore forms very tenacious slags on weld deposits.  It is simply to active to be a strong contender for serious wear resistant materials. But we are always working on it.  (In another life I co-published a paper on Titanium Carbide weld deposits and is available by simply emailing me at miller@cladtechnologies.com .  Be glad to send you a copy.

Aside from forming hard Carbides, Carbide forming elements as mentioned above, also have a contributory effect upon the matrix.  It has been observed that various amounts of austenite will be transformed to martensite in Iron base Complex Chromium Carbide weld deposits.  The extent to which martensite formation occurs is not known to this writer, but observations with a Ferrite Gage in which magnetism is measured in Austenitic Stainless Steels, suggests that martensite formation is significant.

In addition to the above effects on weld deposits, it has been observed microscopically, that Complex Chromium Carbide alloy deposits exhibit a finer Chromium Carbide structure.  From an abrasion viewpoint this appears to be advantageous.  It is known that large blocky Chromium Carbides or Primary Carbides have a tendency to fracture and fall out under stress and therefore contribute to the overall wear of the component.  This can be observed in the wear scars of some ASTM G 65 test results.  We also know that many of the Carbide formers such as Molybdenum, Vanadium, and Titanium for example, act as nucleation sites for Chromium Carbides.  This theory suggests that because there are more sites for Chromium Carbide formation, the resulting deposit structures have a greater volume of  Carbides, but much smaller in actual size.  It then follows that the smaller Carbides inherently have a greater total perimeter to be held in place by the matrix.  Extending this theory further, one would assume that wear resistance would increase simply because these Carbides will not fracture as easy as large blocky Carbides.  Field results appear to confirm this theory.

Our discussion could go on even further to include theories regarding Carbide shape and orientation, but I feel that these topics are well outside the scope of this newsletter.

Suffice it to say that "Complex Carbides Are Complex".  Everything about them appears to be complex.  One thing for sure though;  they are the wave of the future for extreme wear conditions.  Postle Industries Inc., Cleveland, Ohio has a number of these alloys for applications involving extreme abrasion and high temperature.  

Postalloy  2836 SPL   &    Postalloy 2839  SPL 

These are small diameter wires suitably formulated for out-of-position welding.  An excellent product for field and shop applications.

4.  Future Topics

 Since we have covered the topic of Chromium Carbide deposits it would only be natural to follow up our understanding of other Carbide systems.  Our next issue will therefore deal with TUNGSTEN CARBIDES.  These are powerful wear resistant deposits and have some unique properties.  Hope you will enjoy the discussion.

5.  November Is....

 

Aviation History Month

Epilepsy Awareness Month

International Drum Month

National American Indian Heritage Month

National Author's Day

National Diabetes Month

National Hospice Month

National Sleep Comfort Month

Peanut Butter Lovers Month

Nov 1-Jan 1 - Tie One on for Safety

Special Weeks in November:

1-7 - World Communication Week , Vegan Awareness Week

6-12 - Random Acts of Kindness Week

7-13 - National Chemistry Week , National Split Pea Soup Week

8-14 - Pursuit of Happiness Week , Shallow Persons Awareness Week

12-18 - American Education Week

14-20 - National Geography Awareness Week

15-21 - Nat Children's Book Week

21-28 - National Bible Week

Special Days in November:

1-2 - Day of the Dead

2 - Plan Your Epitaph Day , National Men Make Dinner Day

3 - Sandwich Day: Birth Anniversary of John Montague               (Happy Sandwich Day)

4 - Will Rogers Day

6 - Sadie Hawkins Day

8 - Abet and Aid Punsters Day

11 - Martinmas , Vox Populi Day

12 - America Recycles Day

13 - World Kindness Day

14 - National American Teddy Bear Day

15 - George Spelvin Day

17 - World Peace Day , Homemade Bread Day

19 - Have a Bad Day Day

20 - United Nations: Universal Children's Day

21 - World Hello Day

22 - National Stop the Violence Day , Feast of Saint Cecilia (Patron Saint of Music)

23 - Thanksgiving Day

30 - Computer Security Day , Stay Home Because You're Well Day

 

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Our Sponsors

If it weren't for our sponsors, this newsletter would not be possible.  Please consider their products and services in all your future wear related needs.  Thank You.

 
Postle Industries Inc.  http://www.postle.com
Postle offers a complete range of hardface welding alloys to protect equipment from all types of wear.

Sure Alloy Steel Corporation (http://www.surealloy.com)
Wear Control - Design, engineering, and fabrication with over 40 years experience.