Effects of Boron Addition on the Microstructure and Mechanical Properties of (Ti,Ta)(C,N)-Co Based Cermets

Francisco José Gotor Martínez,Ernesto Chicardi

doi:10.3390/met9070787

Francisco José Gotor Martínez, Ernesto Chicardi

Open Access

https://doi.org/10.3390/met9070787

Copy DOI

Journal: Metals	Publication Date: Jul 16, 2019
Citations: 6	License type: CC BY 4.0

Affiliation: Universidad de Sevilla

Abstract

In this work, a titanium–tantalum carbonitride based cermet, with cobalt as the binder phase and boron as a sintering additive, was developed by a mechanically induced self-sustaining reaction process using two different methodologies. The boron additive was added to prevent the formation of brittle intermetallic compounds generally formed during the liquid phase sintering step due to the excessive ceramic dissolution into the molten binder phase. A systematic study was carried out to understand the effects of boron addition on the nature of the phases, microstructure, and mechanical properties of cermets. With the boron addition, the formation of two different boride solid solutions, i.e., (Ti,Ta)B2 and (Ti,Ta)3B4, was observed. Moreover, the nature of the binder was also modified, from the (Ti,Ta)Co2 brittle intermetallic compound (for cermets without boron addition) to ductile and tough (Ti,Ta)Co3 and α-Co phases (for cermets with boron addition). These modifications caused, as a general trend, the increase of hardness and toughness in cermets.

Highlights

Titanium carbonitrides (TiCN) based cermets are potential ceramic-metal composite materials to replace WC-Co hard metals used in the machining industry, in particular, for high speed semi-finishing and finishing work operations [1,2]
As an undesirable effect, the hardness of cermets decreased due to the formation of a soft and ductile binder phase. We present another complementary way to reduce or avoid the formation of brittle intermetallic compounds based on the introduction of boron as an additive to react with the dissolved Ti and Ta during sintering
The addition of boron to (Ti,Ta)(C,N)-Co based cermets during the sintering step caused the formation of two different boride solid solutions, i.e., (Ti,Ta)B2 and (Ti,Ta)3 B4

Summary

Introduction

Titanium carbonitrides (TiCN) based cermets are potential ceramic-metal composite materials to replace WC-Co hard metals used in the machining industry, in particular, for high speed semi-finishing and finishing work operations [1,2]. These interesting applications are possible thanks to the fact that. TiCN-based cermets exhibit high hardness at high temperatures, good thermal stability, relatively high thermal and electrical conductivities, and excellent creep and wear resistances, among other properties [3,4].

Methods

Results

Conclusion