A. M. Freborg, D. B. L. Ferguson, D. C. Li, Deformation Control Technology, Inc., Cleveland, OH; M. Aronov, N. Kobasco, IQ Technologies, Inc., Akron, OH

Summary: It has been well established that carburization of low alloy steels promotes compressive residual surface stress upon quenching, and that compressive surface stresses enhance fatigue life. In an effort to build upon these established facts, a US Army sponsored project is in-progress to improve helicopter gear fatigue life through innovative quenching and the achievement of deeper compressive surface stress. The Army has established a goal to improve the power density and life of helicopter transmissions. Using Pyrowear 53 alloy steel, notched test bars have been heat treated by carburizing, quenching, deep freezing and tempering. The quench methods examined were conventional oil quenching and intensive quenching. Three-point bending fatigue results for these pieces will be reported, as well as differences in residual stress state due to these quenching methods.