Over the past few years, the steelmaking industry has been the subject of attention in the context of the ecological transition. As many other energy-intensive industries, it needs novel materials that can be used under changing process conditions, sustaining very high temperatures or corrosive environments and, at the same time, guaranteeing high-performances and energy efficiency.
Among novel materials, ceramic matrix composites (CMC) can be selected because of their unique thermo-physical properties: they are high-temperature and corrosion-resistant materials able to maintain excellent thermo-mechanical properties in extreme production conditions.
The CEM-Wave project (Novel Ceramic Matrix Composites produced with Microwave assisted Chemical Vapour Infiltration process for energy-intensive industries) aims at developing low-cost ceramic matrix composites production technologies in order to encourage the introduction of these materials in highly energy-intensive production processes such as steelmaking. In more detail, CEM-WAVE is intended to: 1) validate, in a radiant tube furnace, a small-scale CMC-based tube embedded with sensors, substitute the Inconel / stainless steel alloys currently employed 2) introduce to EU companies an innovative CMC manufacturing process based on Microwave assisted Chemical Vapour Infiltration (MW-CVI) technologies.
One of the main problems of CMC materials is that their use depends on their ability to be joined, since the manufacturing of CMC large components is complex and expensive.
This work is focused on the study and development of joining materials and processes for oxide-based ceramic matrix composites (Al₂O_3f /Al₂O₃-ZrO₂)  and non -oxide CMCs (SiC/SiC) for the production of these components.
To achieve this purpose, several materials are proposed and tested as joining materials: new glass-ceramic systems (based on Y₂Ti₂O₇ and YAS (Y₂O₃-Al₂O₃-SiO₂) and high- entropy brazing alloys.
In the case of oxide-based composites, the joining material should be oxidation resistant and able to perform well at high temperature (e.g.>900°C) without any degradation during service life, while SiC/SiC  joints  should operate at higher temperatures (>1200°C) and in harsh environments, where they have to resist corrosion and humidity.
The selected joining materials have been optimized in different ways: the glass compositions are formulated, fulfilling criteria of wettability, CTE matching and thermomechanical compatibility with the CMCs substrate; the brazing alloys have been used because of their low viscosity and infiltration capability in natural CMC porosity. Special attention has been paid to pressureless joining technologies, in order to provide industry-friendly solutions.
Morphological analyses and mechanical characterization by single-lap off-set tests of the joined samples were performed.
 
The research carried out to write this article was funded under the CEM-WAVE project. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 958170. This document only reflects the authors’ view. The European Commission is not responsible for any use that may be made of the information it contains.