SEATTLE (AP) — A metallurgist in Washington has pleaded guilty to fraud after she spent decades faking the results of strength tests on steel that was being used to make U.S. Navy submarines.

Elaine Thomas was the director of metallurgy at a foundry in Tacoma. The foundry supplied steel castings used by Navy contractors to make submarine hulls.

From 1985 through 2017, Thomas falsified results of strength tests intended to show the steel met the Navy’s requirements.

There was no allegation that any submarine parts failed, but authorities said the Navy had incurred increased costs and maintenance to ensure the subs remain seaworthy.

Thomas faces up to 10 years in prison and a $1 million fine when she is sentenced in February.