What is your testing frequency and acceptance criteria for powder purity?
Maintaining exceptional powder purity is a cornerstone of our quality assurance system, directly impacting the mechanical properties, structural integrity, and performance of the final 3D-printed components. Our testing frequency and acceptance criteria are structured in a multi-tiered approach, aligned with international standards and tailored to the specific demands of critical industries.
Our Rigorous Powder Testing Frequency
We implement a comprehensive testing regimen that covers every batch of powder entering our facility, ensuring traceability and consistent quality from reception to final part production.
Incoming Powder Batch Certification: Every new batch of metal powder received from our suppliers undergoes a full suite of tests before being approved for use. This includes chemical analysis, particle size distribution (PSD), and morphology examination.
Per-Build Powder Analysis: For critical applications, especially in the Aerospace and Aviation and Medical and Healthcare sectors, a sample of the powder loaded into the printer is tested for key characteristics, primarily PSD and oxygen content, to ensure it has not degraded during handling.
Reused Powder Monitoring: We rigorously track the number of times powder is reused. After each build cycle, the powder is sieved and blended with a specific ratio of virgin material. The blended powder is then subjected to periodic chemical analysis and PSD checks to monitor for deviation from specification limits, ensuring consistent performance even after multiple uses.
Stringent Acceptance Criteria for Powder Quality
Our acceptance criteria are defined by a combination of material specifications, customer requirements, and the stringent demands of the intended manufacturing process and application.
Chemical Composition and Trace Elements
This is the first and most critical line of defense in ensuring the purity of powder.
Major Alloying Elements: Must fall within the narrow composition ranges specified by standards such as ASTM F3001 for Titanium Alloy Ti-6Al-4V or ASTM F3055 for Ni-Cr superalloys like Inconel 625.
Interstitial Elements: For reactive materials like titanium and superalloys, we enforce ultra-low limits on Oxygen (O), Nitrogen (N), and Hydrogen (H), often below 1000 ppm for oxygen and 100 ppm for others, to prevent embrittlement.
Tramp Elements: Elements like Lead (Pb), Tin (Sn), and Sulfur (S) are controlled to single-digit or even parts-per-million (ppm) levels to prevent hot cracking and grain boundary weakening.
Powder Morphology and Particle Size Distribution (PSD)
The physical characteristics of the powder are vital for achieving high-density parts during Powder Bed Fusion.
Morphology: Powder particles must be spherical and satellite-free to ensure good flowability and consistent powder layering. We use microscopic analysis to confirm this.
Particle Size Distribution (PSD): The PSD must conform to a specified Gaussian distribution, typically between 15-45 μm or 20-63 μm, depending on the machine and application. A tight PSD is critical for achieving optimal surface finish and part density.
Performance-Based Validation
Ultimately, powder quality is validated by the parts it produces.
Mechanical Property Testing: We regularly produce and test witness coupons (e.g., tensile bars) alongside customer parts using the same powder batch. These coupons must meet or exceed the minimum mechanical properties (e.g., Ultimate Tensile Strength, Yield Strength, Elongation) defined for the material.
Defect Analysis: Parts are subjected to Non-Destructive Testing (NDT) like CT scanning to check for porosity and inclusions that could be linked to powder contamination or improper PSD.
Ensuring Long-Term Performance
Our commitment to purity extends beyond the print bed. For components destined for high-stress environments, we offer essential post-processing services that work in tandem with high-purity powders to ensure optimal performance.
Hot Isostatic Pressing (HIP): This process is used to eliminate internal micro-porosity, further enhancing the fatigue life and ductility of parts made from certified pure powder.
Heat Treatment: Precise thermal cycles are applied to achieve the desired microstructure and mechanical properties, the effectiveness of which is dependent on starting with a clean, consistent powder chemistry.
