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There are still debates regarding the mechanisms that lead to hot cracking in parts build by additive manufacturing (AM) of non-weldable Ni-based superalloys. This lack of in-depth understanding of the root causes of hot cracking is an impediment to designing engineering parts for safety-critical applications. Here, we deploy a near-atomic-scale approach to investigate the details of the compositional decoration of grain boundaries in the coarse-grained, columnar microstructure in parts built from a non-weldable Ni-based superalloy by selective electron-beam melting. The progressive enrichment in Cr, Mo and B at grain boundaries over the course of the AM-typical successive solidification and remelting events, accompanied by solid-state diffusion, causes grain boundary segregation induced liquation. This observation is consistent with thermodynamic calculations. We demonstrate that by adjusting build parameters to obtain a fine-grained equiaxed or a columnar microstructure with grain width smaller than 100 μm enables to avoid cracking, despite strong grain boundary segregation. We find that the spread of critical solutes to a higher total interfacial area, combined with lower thermal stresses, helps to suppress interfacial liquation.


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When openings or cracks in flooring cannot be closed, precautions shall be taken to ensure that no employees or flammable or combustible materials on the floor below are exposed to sparks dropping through the floor. Similar precautions shall be taken regarding cracks or holes in walls, open doorways and open or broken windows.

Before regulators are connected to cylinder valves, the valves shall be opened slightly (cracked) and closed immediately to clear away dust or dirt. Valves shall not be cracked if gas could reach possible sources of ignition;

This specification covers four types of joint and crack sealants of the hot applied type intended for use in sealing joints and cracks in Portland cement concrete and asphaltic concrete pavements. However, this specification does not address the properties required of sealants for use in areas of Portland cement concrete or asphaltic pavement that are subject to jet fuel or other fuel spillage such as vehicle and/or aircraft refuel and maintenance areas. The sealants shall be sampled and tested appropriately to examine their conformance with specified values of the following requirements: cone penetration; softening point; non-immersed and water-immersed bond properties; oven aged resilience; and asphalt compability.

9. Passwords:Licensee must immediately notify ASTM of any known or suspected unauthorized use(s) of its password(s), or any known or suspected breach of security, including the loss, theft unauthorized disclosure of such password or any unauthorized access to or use of the ASTM Product. Licensee is solely responsible for maintaining the confidentiality of its password(s) and for ensuring the authorized access and use of the ASTM Product. Personal accounts/passwords may not be shared.

Before attaching the regulator, wipe clean the valve outlet with a clean cloth free of oil and lint and "crack" a secured cylinder by opening the valve slightly then closing it immediately to blow out dust or dirt from the valve outlet. Use two hands on the valve and stand at the side of the valve - never stand directly in front of or behind the valve outlet.

Do not crack fuel gas cylinders due to the chance for the gas to ignite by friction, heating, or other ignition sources. Never crack hydrogen cylinders since the release of compressed hydrogen may ignite by itself. 041b061a72


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