Welcome

A warm welcome to all our new subscribers.  We are glad to have you.  I also want to welcome
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In This Issue

1   Friday the 13th
2   Hydrogen and Delayed Cracking in Hardfacing
3  Postalloy® PS-133   NEW--Chromium Carbide Wire--NEW
4   Humor: Open Mouth - Insert Foot
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Friday the 13th

Ever wonder why Friday the 13th is a bad day?  

The modern reason for this is said to come from Friday, October the 13th, 1307. On this date, the Pope of the church in Rome in conjunction with the King of France, carried out a secret death warrant against "the Knights Templar". The Templars, were a band of warrior monks in Jerusalem and housed in the Kings Temple.  They were to guard the Christians, after the Crusades, against the marauding Muslims.  They became to powerful and wicked and were terminated as heretics, never again to hold the power that they had held for so long. Their Grand Master, Jacques DeMolay, was arrested on that day and tortured and finally crucified or burned at the stake, seven years later.  Legend continues on that day before Demolay died - he predicted to the King and Pope that he would meet them both in heaven within the next year. Fact is... the King and the Pope did die in the year 1314 AD.

It is comforting to know that this year there is only one Friday the 13th.  In 1998 there were three.

........hope my computer doesn't crash while publishing this newsletter. 

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"Hydrogen & Delayed Cracking in Hardfacing "

Hydrogen cracking or delayed cracking is pretty well known in joining applications, but is rarely considered in hardfacing.  Much to the chagrin of well run shops, this ugly critter can show up when procedures are not carried out properly.  A case in point serves to illustrate:

Case History:   A job shop recently overlayed ground engaging teeth made of 8630.  The hardfacing material was 3 layers of Postalloy® 2898 SPL.  The welding process was carried out under 450ºF preheat and interpass temperatures.  After welding, the teeth were inspected, cleaned, painted and shipped.  There were no cracks in the hardfacing when they left the shop, but when they arrived at the customers facility, every tooth was cracked down to the base material.

After a thorough investigation into the customer's welding procedures and visual inspection of the cracks, it became apparent that Hydrogen was the culprit.  The cracks had no paint on the surfaces, which meant that the cracks developed after painting.  If they occurred before painting, we should have found paint in the cracks. A review of the welding procedures indicated that a postheat procedure was ignored or improperly conducted.  Instead of a soak at 300ºF for 3 hours and then a slow cool to room temperature, the teeth immediately came to room temperature in a relatively short amount of time. So how does this implicate Hydrogen?  Well, lets look at the mechanism first.

Hydrogen cracking occurs when hydrogen, which is present in  water, oil or grease is introduced into the weld pool during the welding procedure.  In this case it came from improper cleaning of grease and oil prior to welding.  Hydrogen, being a very small element, roams pretty freely within the weld pool and adjacent Heat Affected Zone (HAZ).  When the weld cools too quickly, the trapped hydrogen is still in movement.  Sort of like when you were a kid, and your parents closed the bedroom door thinking you were off to sleep.  From outside the door, all seemed OK and quiet, but behind the door, there was plenty of activity. You were busy under the covers reading comic books with a flashlight.  Well, the same is true in this case.  The hydrogen atom is busy finding other hydrogen atoms, forming gas, and collecting on some defect well within the steel long after it has cooled.  After hours and perhaps days, enough hydrogen collects and causes enough pressure to lead to cracking.  This usually occurs well after the material has been welded and according to Murphy’s Law, occurs on the customers workplace.

This incident could have been avoided by proper cleaning, and soaking at the recommended postheat procedure.  Soaking at 250-300ºF allows any trapped Hydrogen to escape from the weld and HAZ.  Soak times are roughly 1 to 2 hours per inch of thickness. Once the Hydrogen is gone, then it's safe to cool to room temperature.  In most cases there is no sacrifice in hardness.  Because Hydrogen can be introduced from a number of sources and is usually unknown at the time of welding, soaking acts as the insurance plan to get rid of it. 

It should be noted that not all hardfacing deposits are prone to Hydrogen cracking.  Generally they are confined to the martensitic or tool steel types, such as Postalloy® 2898 and Postalloy® Super-Edge. Austenitic based deposits such as Postalloy® 285, 2850, 2865 and others are not susceptible.  Chromium carbide deposits are not prone either. Having said this however, one must always take into account the base material.  If it is any steel other than Manganese or Stainless, precautions should be taken.  

The potential for Hydrogen to enter the weld pool may be high, but cracking can be avoided by implementing proper preheating, interpass, and postheating procedures.  Don't let "Murphy Law" get the best of you.
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Postalloy® PS-133      New Chromium Carbide Wire

Because of its versatility, PS-133 can be used on a number of applications where severe abrasive wear is troublesome.  It is available in 1/8" and 7/64" diameters.  The data sheet can be viewed and downloaded from our website:  http://www.postle.com/Newsletter/PS133.pdf  

Call us or email sparky at sparky@postle.com with your application.  We'll be happy to help.

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'I was a pilot flying an airplane and it just so happened that where I was flying made what I was doing spying.'
-- Francis Gary Power, U-2 reconnaissance pilot held by the Soviets for spying, in an interview after he was returned to the US.

'Smoking kills. If you're killed, you've lost a very important part of your life.'
-- Brooke Shields, during an interview to become spokesperson for a federal anti-smoking campaign

'I support efforts to limit the terms of members of Congress, especially members of the House and members of the Senate.'
-- Vice-President Dan Quayle

'Are you any relation to your brother Marv?'
-- Leon Wood, New Jersey Nets guard, to Steve Albert, Nets TV commentator

'The streets are safe in Philadelphia. It's only the people who make them unsafe.'
-- Frank Rizzo, ex-police chief and mayor of Philadelphia

'The doctors X-rayed my head and found nothing.'
-- Dizzy Dean explaining how he felt after being hit on the head by a ball in the 1934 World Series

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