Titanium Alloys - Metallographic Sample Preparation

Metallographic preparation of titanium alloys can be accomplished easily when using OnPoint Abrasives' consumables and procedures. We have provided step by step instructions for metallographic sample preparation of titanium alloys below.

Sectioning Recommendations: Achieving optimal results in the resurfacing process hinges on precise cutting techniques. To minimize subsequent grinding steps, it is strongly advised to cut the specimen as close to the Point of Interest (POI) as feasible.

For titanium alloys, our top-tier suggestions involve utilizing either TitanSec abrasive blades or our General Purpose diamond blade. TitanSec abrasive blades employ SiC particles embedded in a rubber bond, yielding a high-speed cutting blade that effectively preserves the integrity of the specimen.

There may be scenarios where traditional metallurgical sectioning proves impractical, particularly when dealing with very small or delicate specimens such as thin wires or foil-like materials. In such instances, employing fundamental cutting tools like scissors, paper cutters, or bolt shears is more suitable. Notably, for minute samples like biomedical device components, a common approach involves solely relying on grinding procedures to attain the desired depth, thus bypassing the need for initial sectioning altogether. 

Mounting Recommendations: To produce optimal metallographic mounts for titanium alloys, consider EpoMount epoxy powder for compression specimen mounting. The robust hardness of the mineral infused epoxy ensures exceptional preservation of specimen edges and facilitates uniformity across the complete mount surface.

For titanium alloy specimens necessitating castable mounting, it is advised to utilize our EpoPro liquid epoxy system. Employing a vacuum impregnation chamber while conducting the castable mounting procedure effectively eradicates undesired air bubbles from the epoxy material, enabling its penetration into the intricate recesses and geometries of your titanium alloy specimen. This method is highly recommended for casting metallographic samples of titanium alloys, although it may not be nessesary in all instances.

Grinding and Polishing Recommendations: OnPoint's guidelines for grinding and polishing serve as a reference for preparing samples for metallographic analysis. Our titanium alloy procedure is specifically designed for employment on an automated polisher featuring Central Force capability. This procedure uses a contra directional pattern between the working wheel and specimen holder.

When using polishers that possess exclusively Individual Force capability or when opting for manual polishing, the operator should commence the procedure from step number 2. Adjustments are also necessary when using Individual Force or manual polishing. We advise adopting a complimentary directional pattern. For Steps 1 and 2, maintain an RPM of 200/base and 150/head. For steps 3 and 4, reduce the RPM to 150/base and 100/head. It might be necessary to extend polishing durations for all steps.

Tech Note: For enhanced grain boundaries, skilled metallographers may include hydrogen peroxide (30%) mixed in colloidal silica. Mix at 5 to 1 ratio (colloidal silica to H2O2). This step should only be performed by qualified personnel and should always include the use of proper PPE.

Note: Clean specimen by gently wiping the surface with a cotton ball under running water. Repeat until all visible contamination is removed. Use of an ultrasonic cleaner is highly recommended for samples with high porosity content or intricate geometries.