GE GTD-111 superalloy heat-treatment patent

Another type of externality is intellectual property. General Electric patented a nickel-base superalloy called GTD-111 in the mid-1970s, and it became part of a lot of their land-based turbines, and in some cases aircraft turbine engines. Starting in the 1980s and 90s, as the patent was expiring, other people realized this was a good alloy with good high-temperature properties, and they started designing it into their engines.