» »
Cladding
a roll bond clad plate has the lowest bond shear strength of the three techniques described in this article . It is the major production method for stainless-clad steel plates . Hot roll bonding accounts for more than 90 % of the clad plate production worldwide .
Explosion bonding Explosive bonding uses the very-short duration , highenergy impulse of an explosion to drive two surfaces of metal together , simultaneously cleaning away surface oxide films and creating a metallic bond . It resists the most aggressive hydrogen charging scenarios .
Figure 3 . Cladded tubesheet- matching material of tubes and cladding .
temperature process streams containing high levels of nitrogen compounds such as ammonia or cyanides , particularly under reducing conditions . Cladding with nickel alloy material is successfully used for protection against nitriding . An example of this is the weld overlay application on the shell side of an effluent cooler in the synthesis loop in ammonia plants , which is beneficial in resistance to nitriding and hydrogen embrittlement .
Application technologies There are different techniques and technologies used in cladding applications , among which three are the most common :
Hot roll bonding Produced when a steel mill heats the steel and corrosionresistant alloy together and rolls them as one package . The rolling , under high temperature and pressure , causes the two metals to clad together . It is generally accepted that
Weld overlay Weld overlay is a fusion deposition of corrosion-resistant alloy onto a steel or alloy steel substrate . Usually , weld overlay is done in place , after the pressure vessel has been through many of the fabrication steps , but not always . In many cases , dilution concerns necessitate the use of ‘ butter passes ’ and over-alloying in an attempt to overcome the issues of dilution .
Special care for application in hydrogen service Clad disbonding tests should be performed on any 1.25Cr- 1 / 2Mo and 1Cr-1 / 2Mo vessel that is in high-pressure hydrogen service that may be subjected to rapid cool down conditions from service . Vessels that have experienced disbonding have been subjected to a rapid shut down . The rapid shut down does not allow hydrogen diffusion before reaching ambient temperature . Hydrogen disbonding tests on the proposed overlay weld procedures shall be done per ASTM G146 , at the testing conditions defined by the purchaser .
Bimetallic ( duplex ) tubing Bimetallic tubing consists of two concentric tubes of different materials for applications with various corrosion resistance on the shell and tube sides . An
Figure 4 . Example of welded incoloy plug to incoloy cladded tubesheet .
24 Heat Exchanger World April 2024 www . heat-exchanger-world . com