The effect of chemical vapor infiltration process parameters on flexural strength of porous {\alpha}-SiC: A numerical model

TL;DR

This study develops a numerical model linking chemical vapor infiltration process parameters to the flexural strength of porous {}-SiC ceramics, enabling process optimization for improved material performance at high temperatures.

Contribution

A novel nonlinear single pore model combined with a thermo-mechanical damage model to predict flexural strength based on CVI process parameters.

Findings

Specimens with >30% porosity need temperatures below 1273 K for strength.

Porosity <30% specimens are temperature-independent.

Model aids in optimizing CVI process for desired strength.

Abstract

The flexural strength variability of {\alpha}-SiC based ceramics at elevated temperatures creates the need for an Integrated Computational Materials Engineering (ICME) framework that relates the strength of a specimen directly to its manufacturing process. To create this ICME framework a model must first be developed which establishes a relationship between the chemical vapor infiltration (CVI) process and parameters, the resulting mesoscale pores, and the overall macroscale flexural strength. Here a nonlinear single pore model of CVI is developed used in conjunction with a four-way coupled themo-mechanical damage model. The individual components of the model are tested and a sample system under a four-point bending test is explored. Results indicate that specimens with an initial porosity greater than 30% require temperatures below 1273 K to maintain structural integrity, while those with initial porosities less than 30% are temperature-independent, allowing for optimization of the CVI processing time without compromising strength.