Method of cryogenically hardening an insert in an article, and article made thereby.

摘要

A method of cryogenically hardening and expanding an insert in an article is disclosed. Particularly, gray iron piston ring insert (14) having an austenitic matrix is treated in a piston body (12) by impinging a cryogenic medium thereon. This changes the matrix microstructure of the insert to at least about 25 Vol.-% martensite and desirably increases the hardness level thereof to at least about 95 on the Rockwell "B" scale in the desired regions thereof. The volume of the insert is also expanded to be more securely received in the piston body.