Meaning
Grain diameter spread is the quantitative map of different particle categories within a total volume of metallic powder, ranging from fine dust to coarse fragments. Inside the quality control laboratory, particle size distribution determines how the material flows into molds and how effectively it will sinter during high temperature treatment. High percentages of very fine particles improve the final density of the part but may increase the risk of atmospheric oxidation.
This metric stops being useful if it only lists the average size without identifying the specific range of diameters present in the batch.
Analytical Sieving
Mechanical separation through screens of known mesh sizes provides the first layer of data for large batches of metal powders. Because particle size distribution often follows a normal bell curve, operators look for specific cutoff points known as D10, D50, and D90 values. These numbers indicate the diameter below which ten, fifty, or ninety percent of the sample weight exists.
Precise control over these bands ensures that the powder works in the specific hardware of the end user. If the spread is too wide, small particles will fill the gaps between large ones to increase the apparent density.
Laser Diffraction
Measurement of light patterns as individual grains pass through a beam allows for the identification of much finer sub-micron particles. Since particle size distribution changes as a function of the gas jet stability in the nozzle, this data provides feedback for machine adjustment. High consistency between batches is required for medical and aerospace applications where reliability is paramount.
This electronic testing provides a faster and more repeatable alternative to manual sieving. The results allow for the exclusion of oversize grains that might disrupt a printing process.
Geometric Impact
Final mechanical properties of the forged steel parts depend heavily on the average diameters of the starting material grains. When particle size distribution is tightly controlled, the shrinkage during sintering remains predictable across the whole part. This reduces the need for extensive post-process machining to reach the desired final dimensions.
High consistency between multiple batches allows for automated production cycles with minimal downtime for recalibration. Measuring this property remains the standard procedure for every powder shipment in the industry.
