Quality assurance for gas-atomized powders can be challenging if you are not familiar with the production process. Part 1 of this series provided A Gas Atomization Primer.
This article explores one of the first major sources of contamination risk for titanium powders, which occurs as soon as the raw material electrode is inserted into the atomizer to begin production. The electrode is heated to a molten state using a crucible. Crucibles are typically made of refractory material.
Refractories are heat-resistant materials that constitute the linings for high-temperature furnaces and reactors and other processing units. In addition to being resistant to thermal stress and other physical phenomena induced by heat, refractories must also withstand physical wear and corrosion by chemical agents. Refractories are more heat resistant than metals and are required for heating applications above 1000°F (538°C).
-The Refractories Institute
While refractory properties are obviously advantageous to melting titanium and other pre-alloyed metals to produce powder, the intense process can cause small pieces of refractory to chip off into the molten metal.
What does refractory contamination do?
The presence of refractory in titanium powder will greatly compromise the material's fatigue performance.
What's the solution?
The only way to eliminate the risk of refractory contamination is to eliminate the use of refractory in the crucible, nozzle, and cement housing of gas atomizers. The absence of any refractory components
in the Electrode Inert Gas Atomization (EIGA) process, utilized by Carpenter Additive, minimizes the risk of high-density contaminants.
If you're experiencing fatigue performance issues in your printed titanium parts, ask your supplier if refractory may be the cause.