Vacuum brazing of precipitation hardening stainless steel without losing its mechanical properties

Abstract

Precipitation hardening stainless steel is heat treatable alloy which is used in age hardened condition. If vacuum brazing is carried after aging, it loses it mechanical properties due to over-aging. To avoid this, an innovative vacuum brazing method coupled with heat treatment was developed and proved by experiments. In the method, brazing temperature was varied from 1030 C to 1050 C which was matching with solutionising temperature of precipitation hardening stainless steel. Immediately after brazing (brazing cycle= solutionising cycle) the samples were quenched from brazing temperature by ultra pure inert gas. It was carried out in high vacuum high temperature furnace which has the provision for inert gas quenching. Quenching gas pressure was varied form 900 m. bar to 1300 m. bar. Filler material used in the study was gold-18% nickel alloy. Aging treatment was carried out at 496 C after brazing. Parameters for maximum joint strength and maximum mechanical properties of precipitation hardening stainless steel were arrived and discussed in detail.