Alain etal.-- This paper by Duncan etal. from ICCF-18 identified by Alain remind me of an experience involving stress corrosion in Ni-Cr-Fe alloy 600 over 40 years ago. The material specification being used to procure the Ni-Cr-Fe material did not control the concentration of Niobium. It was not believed to be an element that need to be controlled. However, some heats of material were subject to stress corrosion and some were not. The ones coming from one vendor were generally good and ones coming from another vendor were not so good. It turned out that the vendor producing the good heats--those that did not corrode--had added Nb in a very small amount--several parts per million--to its heats, still meeting the specification, since this element, Nb, was not controlled by the specification. The small amount of Nb turned out to tie up carbon which was allowed to a small extent per the specification. It reacted with the carbon in the grain boundaries and prevented stress corrosion from occurring. The micro stress patterns were changed and internal stress small. The local energy necessary for the stress corrosion cracking did not develop.
Embrittlement is what happened in the welds of hulls of Liberty Ships that broke up under stressing and fatigue during WW1. The welds were embrittled by ionization of water in stick electrodes used to weld sections of the hulls together. The migration of the hydrogen to local defects caused internal pressure and the embrittlement. The lesson was: Do not to use wet electrodes for welding steel. The devil is in the details. Separately, a good mechanism for controlling cracks may be the introduction of water during alloying. Various small amount of crystals of hydration can be added to a preparation of an alloy using powder metals mixed and diced in a cryogenic ball-milling machine. (Such a device uses liquid N-2 as the liquid in the ball milling process to get very fine--maybe nano scale--particles of an alloy and the hydrated crystal. The N-2 is nice, since it prevents the agglomeration of particles by coating each particle with a layer of N-2. Very good mixing is possible. The slurry mixture is poured into molds under a vacuum to keep stray atoms out and the N-2 is allowed to evaporate under the vacuum and added temperature and pressure. Pressure bonding is accomplished with the hydrated crystal in the bonded metal lattice. During the heating and pressure bonding process, the water of hydration changes to O-2 and H-2, the O-2 reacts to form a metal oxide and the hydrogen collects in defects to form an internal pressure and embrittlement. The metal atoms bond together being very pure with little on no excess heat and whatever pressure it takes. (He may be used in the pressure bonding process once the N-2 is off gassed.) There is no oxide reduction necessary to get the metal to bond well.. The small amount of O-2 reacts locally at the point where the crystal of hydration ends up in the mix. The grains are very small and well controlled in size considering the amount of water of hydration used in the mix. For magnetic materials like Ni and Pd these boundaries may even be oriented in a desired direction during bonding. Deuterated water of hydration crystals may be a good sauce in this mix for Pd, giving pockets of D-2 at the grain boundaries without preloading. Anybody wanting a patent on this process idea should get to work. (smile) Bob ----- Original Message ----- From: Alain Sepeda To: Vortex List Sent: Sunday, March 23, 2014 8:26 AM Subject: Re: [Vo]:Stimulate embrittlement you can add to that the observation by ENEA that 100 structure of the surface (can someone explain me... it seems meaning just that cutting is done parallel to the cube facets) https://mospace.umsystem.edu/xmlui/bitstream/handle/10355/36833/ExcessPowerDuringElectrochemical.pdf?sequence=1 2014-03-23 15:48 GMT+01:00 Teslaalset <robbiehobbiesh...@gmail.com>: The topic of creating the right NAEs touches my recent querries for optimizing Nickel embrittlement. There's lots of info available in the public and scientific domain on reducing embrittlement of Nickel, hinting at some of the main possible causes. Some of those causes: a.. Copper - Nickel alloys, where oxidized copper clusters in nickel alloys can form H2O and Copper, where the local H2O can cause very high pressures that in their turn can cause cracks (and holes). My association with this is the use of the Cu-Ni-Mn alloys Celani used for his recent research. b.. Carbon to enforce Nickel alloys. Under pressure and elevated temperatures Hydrogen and Carbon can form pockets of Methane causing embrittlement. Looking to causes of embrittlement of pure Nickel there are not so many hints that I could find so far. I guess absorbtion and desorbtion at certain rates are the most common known causes to create Nickel embrittlement. Are there others known? Last thing I would like to mention is the remarking indication of Defkalion of modifying Nickel lattice from FCC to C4 or a Pm3m structure, Any clues on how they would do this?
