Alloy 718 for oilfield applications

Alloy 718 (UNS N07718) was developed for use in the aircraft gas turbine engine, but its unique combination of room temperature strength and aqueous corrosion resistance make it a candidate for oilfield fasteners, valves, drill tools and completion equipment. Its popularity stemmed in part from its availability in a wide range of bar sizes from distributors. As oil and gas well environments became more severe, stress corrosion and hydrogen embrittlement failures in production equipment were experienced. This drove the evolution of the chemistry and microstructure that distinguishes today's oilfield grade 718 from aerospace grades. This paper reviews the development of the grade and its applications and describes some of its unique characteristics, testing and manufacturing methods. Consumption of 718 in the oilfield has probably reached its peak. Offshore production from deep sour fields created a demand for stronger, more corrosion resistant alloys has led to the development of new alloys that have begun to erode 718's market share. The last section of the paper describes these new alloys. (AU) © 2010 by The Materials, Metals, & Materials Society. All rights reserved.