MECHANICAL PROPERTIES OF FORGED TUNGSTEN HEAVY ALLOYS

Ondřej Kovářík,Jiří Čapek,Michal Hajíček,Jan Siegl,Jaroslav Čech,Jakub Klečka

doi:10.14311/app.2020.27.0149

Abstract

Tungsten heavy alloys are composite materials containing spherical tungsten particles embedded in binder matrix. Their excellent mechanical properties can be further improved by rotary forging. This paper aims to gain deeper understanding of the forging process by investigating the local elastic modulus, hardness, and residual stress of individual phases in W6Ni3Co pseudo-alloy. The resulting global properties of the composite material such as stress-strain behavior, fracture toughness and fatigue crack growth rate behavior are also studied. The results show that sintered and quenched material consists of highly textured matrix containing nearly perfect single crystal spheres of pure W. The rotary forging leads to significant lattice deformations destroying the texture and significantly increasing the hardness of both WNiCo matrix and W particles and making residual stresses in W particles anisotropic with increased compression along the longitudinal axis of the forged part.

Highlights

Tungsten heavy alloys (WHA) are two phase materials consisting of tungsten particles embedded in binder matrix typically consisting of W-Ni-Cu, W-Ni-Fe, WNi-Co or W-Ni-Fe-Co
This paper summarizes global or macroscopic engineering properties of the W6Ni3Co tungsten heavy alloy in as sintered and quenched (SQ) and forged and annealed (FA) states
The observed changes are related to the local changes of the residual stress distribution, microhardness and elastic modulus of individual phases of the WHA, i.e. of the Ni rich matrix and W particles

Summary

Introduction

Tungsten heavy alloys (WHA) are two phase materials consisting of tungsten particles embedded in binder matrix typically consisting of W-Ni-Cu, W-Ni-Fe, WNi-Co or W-Ni-Fe-Co. These materials feature good wear resistance and high strength, density, thermal conductivity, corrosion resistance and radiation absorption These properties determine the use of WHAs for counterweights, kinetic penetrators, electrical contacts, radiation shielding etc. The high temperature application of WHA’s is limited by the melting point of Ni rich binder which lies above 1400 °C. Despite this limitation, WHA’s are considered as candidate materials for first wall of future fusion devices [1, 2]. The mechanical properties of WHA’s can be compared to pure tungsten. The observed changes are related to the local changes of the residual stress distribution, microhardness and elastic modulus of individual phases of the WHA, i.e. of the Ni rich matrix and W particles

Experimental

Results

Local Properties

Conclusion