Theoretical and Experimental Investigation on SiC/SiC Ceramic Matrix Composites Machining with Laser Water Jet

Bai Cheng,Ye Ding,Lijun Yang,Yuan Li

doi:10.3390/app12031214

Abstract

SiC/SiC ceramic matrix composites (CMCs) are widely applied in the aerospace and nuclear industries due to their excellent material nature (strength, hardness, and irradiation tolerance) at high-temperature loads. However, high-quality machining cannot be easily realized because of the anisotropic material structure and its properties. In this study, a laser water jet (LWJ) was adopted for CMCs machining. Firstly, the finite element model (FEM) was established describing a representative three-dimensional microstructure including weft yarn, warp yarn, SiC base, and the pyrolytic carbon (PyC) fiber coating. The temperature distribution, as well as its evolution rule on substrate surface under LWJ machining, was analyzed. Moreover, a single-dot ablation test was carried out to verify the accuracy of the numerical simulation model. Secondly, the variation in maximum temperatures under different laser pulse energy was obtained by means of FEM. Nonetheless, a non-negligible deviation emerged in the ablation depth of the numerical calculation and experimental results. Although the simulation results were obviously superior to the experimental results, their proportions of different machining parameters reached an agreement. This phenomenon can be explained by the processing characteristics of LWJ. Finally, single-row and multi-row scribing experiments for CMCs with 3 mm thickness were developed to clarify the processing capacity of LWJ. The experimental results indicated that single-tow scribing has a limiting value at a groove depth of 2461 μm, while complete cutting off can only be realized by multi-row scribing of LWJ. In addition, the cross-section of CMCs treated by LWJ presented a surface morphology without a recast layer, pulling out of SiC fibers, and delamination. The theoretical and experimental results can offer primary technical support for the high-quality machining of CMCs.

Highlights

As a type of emerging composite, SiC ceramic matrix composites (CMCs) have been widely employed in the aerospace and nuclear industries owing to their unique material parameters including a better strength to weight ratio, high toughness, superior resistance to heat effects, and low density [1,2,3]
It is worth noting that the density of CMCs material is only 30% of superalloys, which is beneficial for its application in the aerospace field [5]
These results indicate that CMCs removal only takes place during the laser pulse duration and the following one

Summary

Introduction

As a type of emerging composite, SiC CMCs have been widely employed in the aerospace and nuclear industries owing to their unique material parameters including a better strength to weight ratio, high toughness, superior resistance to heat effects, and low density [1,2,3]. It is worth noting that the density of CMCs material is only 30% of superalloys, which is beneficial for its application in the aerospace field [5]. Due to their excellent material performance, researchers have shown an increased interest in application studies of CMCs. a series of challenges have been raised by the outstanding material properties for CMCs machining. According first law law of of thermodynamics, thermodynamics, the the governing governing equation equation of of transient transient heat transfer which describes the process of time-dependent heat conduction in the material heat transfer which describes the process of time-dependent heat conduction in the matedomain subject [17], can be written as Equation (1): rial domain subject [17], can be written as Equation (1): ρc pρ∂T c p ∂=. For a three-dimension Cartesian coordinate system, Equation (1) can be rewritten as as follows: follows: ρc p ∂T ∂ ∂T

Methods

Results

Conclusion