Ceramic matrix composites (CMCs) are a unique class of materials that combine different compositions of ceramics to achieve optimized properties. Their density and radiopacity makes them challenging to analyze by NDE techniques such as CT. Robo-Met.3D® provides a proven workflow to analyze the structure and defect profiles of these materials.
This recipe evaluates a SiC-SiC CMC fabricated using polymer infiltration and pyrolysis. This step-by-step workflow provides a starting point that can be customized to analyze your CMCs with Robo-Met.
Read also: Metallographic Workflow for Steels and Ferrous Metals
The sample is conventionally cold mounted in a 1 ½” mount. The imaging area is highlighted in red.
Most workflows can be divided into a planarizing step that is not repeated, and grinding/polishing steps for material removal and surface smoothing. In this case, we used a 15µ Dia-Grid Diamond Disk for planarization.
Maintaining moisture on the pads is essential to successful automated metallography. The final on-pad cleaning step provides a better imaging surface.
Robo-Met.3D® Comparisons for a SiC/SiC CMC
Robo-Met.3D provided high resolution images using the 10x and 20x objectives described above. The 20x objective image was useful to visualize the coating on the fibers, as well as unreacted silica from the pyrolysis process. The different phases are clearly segmentable using a WEKA routine.
Segmented (Pores- red , fibers- green, matrix- purple, unreacted silica- yellow)
This workflow provided a linear material removal of about 3.8µ per polishing step, with an R squared value of 0.998 over 54 sections. The removal results (focal plane of section versus section number) are plotted on the above figure, which demonstrates a highly linear material removal for the CMC sample.
This provides essential input into our 3D reconstruction models.
The wide variety of materials that we analyze for clients has given us extensive experience in developing workflows suited to materials such as aerospace alloys and polymer and additively manufactured materials, among others. Contact us to jump-start your utilization of Robo-Met. We’ll be happy to consult with you to create a custom workflow to characterize your materials.