This book gives a brief history of the development of Alloy 625 and a detailed account of its physical, mechanical, and corrosion properties. It also addresses different types of microstructural changes the Alloy 625 undergoes at intermediate temperatures; provides details of properties deterioration due to such microstructural changes; assesses the alloy damage during the in-service inspection of plants; and provides criteria for the damage evaluation for various destructive and non-destructive testing. It combines the industrial data and literature together in one place for damage assessment of service exposed Alloy 625 components. This book serves as a guide to practicing engineers in the industry interested in the use of Alloy 625 and in academia for students pursuing advanced courses in materials science. Alloy 625 is a versatile nickel-chromium-molybdenum alloy known for its unique combination of high strength, excellent fabricability and weldability, and outstanding corrosion resistance.