Design of cemented carbide with Ni-based superalloy binder strengthened with y’-Ni3Al precipitates
Sammanfattning: Replacement of cobalt in cemented carbides has gained in attention recently because threats of regulations due to health issues (cancerogenic effect), increased demand from the electric vehicle industry and the questionable extraction from countries like Democratic Republic of Congo. In this report the use of Ni-based binder as an alternative binder for cemented carbides has been explored. The design is based on producing a Ni-based superalloy binder which contains dispersed Ni3Al Gamma Prime (γ’) -phase precipitates in the binder matrix. The investigation focuses on the design of cemented carbide compositions and processes that ensures the formation of γ’- precipitates, the control of their morphology and distribution as well as the effect of heat treatment. To do this a Ni-Al master alloy has been designed that enables the formation of γ’-precipitates in WC-Ni-Al-X systems, produced by conventional powder metallurgy process including standard free sintering. Furthermore, the addition of usual elements in the cemented carbide industry (such as Ti, Cr, Ta, Nb) and their effect on the stability of γ’-precipitates has been investigated. A method to reveal the precipitates including ion-polishing and electro-etching has been developed. Basic mechanical properties such as hardness and toughness have been investigated, revealing particular crack propagation in Ni-based binder reinforced with γ’-precipitates. It was found that the common variables in cemented carbide manufacturing influence all aspects regarding the stability of γ’-phase. By varying the powder type, binder composition and content, the carbon balance, the WC grain size and the heating/cooling steps; the formation of γ’-precipitates (size, morphology, distribution, etc.) can be controlled to tailor the properties of the cemented carbide.
HÄR KAN DU HÄMTA UPPSATSEN I FULLTEXT. (följ länken till nästa sida)