Development and Properties of Tungsten-bearing Stainless Maraging Steel

Abstract

The effects of the tungsten content and heat treatment on the mechanical properties and microstructures of Fe-11Cr-10Ni-xW-0.4Al-0.3Ti stainless maraging steels (where the composition is in approximate weight per cent) have been investigated. The increase 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-degrees-C because of enhanced precipitation of eta-Ni3Ti phase. Above 500-degrees-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 eta-Ni3Ti phase in the W2 alloy, and the orientation relationship between eta-Ni3Ti precipitate and martensitic matrix was (011)alpha' parallel-to (0001)eta [111BAR]alpha' parallel-to [1120BAR]eta.