Development and properties of tungsten-bearing stainless maraging steels

Abstract

The effects of the tungsten content and heat treatment on the mechanical properties and microstructures of Fe-11 Cr-10 Ni- xW-0.4Al-0.3Ti stainless maraging steels (where the composition is in approximate weight per cent) have been investigated. The increases in tungsten content from 2 to 5 wt.% increases the yield strength accompanied by decreases in elongation and Charpy impact energy. The hardness increases with increasing aging temperature up to 500°C because of enhanced precipitation of ν-Ni 3Ti phase. Above 500°C, the hardness decreases with increasing aging temperature mainly owing to the formation of reverted austenite. The desirable combination of a high yield strength (1280 MPa) with a good Charpy impact energy (80 J) was obtained in 2 wt.% W alloy (W2 alloy). The strengthening precipitate formed during aging of tungsten-containing stainless maraging steels was identified as ν-Ni 3Ti phase in the W2 alloy, and the orientation relationship between ν-Ni 3Ti precipitate and martensitic matrix was (011) α'| (0001) ν [1 1 1] α'|[11 2 0] ν