Page 19 - Demo

Issue 143 August 2024 PCMI Journal 19
PCM of Difficult-to-Etch Metals and Alloys: Nickel- and Cobalt-Based Superalloys
Emeritus Professor David Allen, Cranfield University
Hastelloy D alloy, a nickel-silicon-copper material, was also invented during the
1920s. The latest version of this alloy, Hastelloy D-205 alloy, is used today in
chemical plants that use hot, highly-concentrated, sulfuric acid.
The 1950s also marked the beginning of significant change for the company. New
high-temperature wrought alloys were also being added. Multimet alloy, a
nickel-cobalt-chromium-molybdenum-tungsten material, appeared in 1949, and
in 1950, the cobalt alloy L-605, now also known as Haynes Alloy 25 or Alloy 25,
was first manufactured.
A very wide range of nickel-based superalloy families have been developed as
shown in Table 3.
Table 3. Some nickel-based superalloy groupings.
Superalloy UNS Werkstoff # General description
Hastelloy B N10001 2.4800 First generation Ni-Mo superalloy
Hastelloy C-276 N10276 2.4819 Ni-Mo-Cr-Fe-W-Co-V
Hastelloy R-235 N06235 - Vacuum-melted Ni-Cr-Fe-Mo-Ti-Al
Hastelloy X N06002 2.4665 Ni-Cr-Fe-Mo
Inconel 600 N06600 2.4816 Ni-Cr-Fe hardened only by cold work
Inconel 601 N06601 2.4851 Utility Ni-Cr-Fe alloy resists heat and
corrosion
Inconel 617 N06617 2.4663a Ni-Cr-Co-Mo high strength at over 1800°F
Inconel 625 N06625 2.4856 High-strength, corrosion- resistant Ni-Cr
alloy, service temperatures up to 1800°F
Inconel 718 N07718 2.4668 Age-hardenable, high-strength, corrosion-
resistant Ni-Cr alloy used up to 1300°F
Inconel X-750 N07750 2.4669 Age-hardenable Ni-Cr alloy
René 41
(General Electric)
N07041 2.4973 Vacuum-melted age-hardenable Ni-Cr-
Co-Mo-Fe-Ti-Al high temperature
superalloy
Udimet 500 N07500 2.4983 Ni-Cr-Co
Udimet 700 N07700 2.4636 Ni-Co-Cr-Mo-Ti-Al-Fe
Waspaloy
(Pratt & Whitney)
N07001 2.4654 Age-hardenable Ni-Cr-Co-Mo-Ti-Al-Fe
superalloy
Published information on etching of difficult-to-etch materials
Presentations on difficult-to-etch metals and alloys have been given previously
at PCMI conferences and webinars [6-8] and a Cranfield University – PCM
Companies Consortium report (restricted to consortium members until 2006)
has also been written [9]. It concentrated on determining suitable etchants for
difficult-to-etch materials, especially electrolytic etchants, with reduced “Health,
Safety and Environment” (HSE) impacts.