ATI has developed ATI 642™† alloy, a new Ni-Cr-Mo corrosion-resistant alloy that displays significant resistance to sensitization from the effects of hot-clad bonding and welding operations. The new alloy is unique because of its substantial Fe content, which gives it a significant cost advantage over Ni-based alloys of similar performance, while still containing enough Ni to provide SCC resistance superior to 6Mo stainless steels. It has a PREN value in excess of 40, which provides useful resistance to chloride environments such as seawater.

This paper will present the results of chloride stress-corrosion cracking (SCC), intergranular attack (IGA), and critical pitting temperature (CPT) corrosion tests, as well as results of tensile tests and Charpy impact energy tests. Testing was conducted in both the solution-annealed condition and following a sensitizing heat treatment that simulates typical exposure during the hot-clad bonding fabrication process. The microstructures of the new alloy in the solution-annealed, sensitization-heat-treated, and welded conditions will also be shown and discussed. The test results and microstructures will be compared to those of other alloys traditionally used by the oil and gas and chemical processing industries.

Subject
Test methods, Materials, Corrosion resistant alloys, Stainless alloys, Corrosion rate, Materials performance, Microstructure, Nickel based alloys, Molybdenum alloys, Corrosion resistance, Titanium alloys, Alloys, Chloride stress corrosion cracking
Keywords:
Alloy 642, pitting corrosion, stress corrosion cracking, intergranular corrosion, phase stability, weldability, impact energy, clad pipe
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2021
Association for Materials Protection and Performance (AMPP)
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