Alloy Stoichiometry and Gas Entrapment Control in Atomized Powders
Controlling melt superheat and nozzle pressure limits vapor pressure elemental loss while helium purge or vacuum degassing eliminates micro-cavity gas voids.
Carney Funnel
Meaning
Standardized testing instruments represent the physical apparatus used to measure the flow rate of non-free-flowing metal powders under gravity. This laboratory instrument governs the quality control of feedstocks used in powder metallurgy and additive manufacturing, with its application limited to powders that cannot pass through a standard hall funnel. Utilizing a carney funnel provides a reliable and repeatable method for evaluating the flow characteristics of coarse or irregular powder batches.
This measurement is critical for predicting how the powder will behave in automated feeding and spreading systems.
Measurement Mechanism
The testing procedure involves placing a specified weight of powder into the conical vessel and measuring the time it takes to exit through the bottom orifice. The orifice of this instrument is wider than that of a hall funnel, which allows cohesive powders to flow without blockages. This test is conducted under controlled temperature and humidity conditions to prevent moisture from affecting the powder flow.
The measured flow rate is expressed in seconds per fifty grams, providing a clear metric for powder quality. Consistent flow behavior is essential for achieving a uniform density in the sintered or printed component.
Powder Classification
Analyzing powder flow with this apparatus helps process engineers determine if a powder batch requires drying or other pre-processing steps. Powders with irregular shapes or high friction surfaces will exhibit slower flow times or fail to flow altogether. This testing allows the selection of appropriate powder feedrates on the production line.
Sourcing high-quality metal powders involves verifying that their flow rates fall within acceptable limits to prevent clumping during deposition. This verification is crucial for maintaining high production speeds and reducing scrap rates.
Quality Control
Regular calibration of the test orifice is required to ensure that wear does not alter the flow measurements over time. Sourcing a certified calibration powder allows laboratories to verify the accuracy of their testing equipment. The results of these flow tests are used to qualify powder batches for demanding industrial applications.
This simple and rapid testing method is a staple of quality control departments in powder manufacturing plants.
Inert Gas Atomization Fundamentals for High Alloy Tool Steel Powder Production
Gas atomization of high alloy tool steel requires matching gas-to-melt ratios and superheat to restrict internal argon void volume under 0.05 percent.