Standardized X-ray tomography testing of additively manufactured parts: A round robin test

Micro computed tomography (microCT) allows non-destructive insights into the quality of additively manufactured parts and the processes that produce them. MicroCT has been used widely in this industry but the use of this technique is often time consuming and costly which reduces its potential impact and the benefits associated with its use. By using standardized test procedures, the analysis time and cost can be minimized and confidence in obtained results increased. A round robin test was conducted as follows: a series of standard test procedures (part sizes and shapes and test protocols) were applied - using one microCT system - to identical parts produced on a variety of metal additive manufacturing systems (specifically laser powder bed fusion systems). These are simple parts: a 10 mm cube, a 15 mm diameter vertical-built cylinder and a basic topology optimized example part - a bracket. The 15 mm diameter cylinder acts as witness specimen for the build of the complex part. All these were produced in Ti6Al4V, and in some cases parts were provided with variations in process parameters or manufacturing conditions which led to different types of intentional manufacturing flaws or defects. Various intentional and unintentional flaws were identified and quantified. The major result shown is that the analysis of a simple 10 mm cube clearly identifies incorrect process parameters even for very low levels of porosity, with unique porosity distributions and characteristics. It is found that generally this porosity extends to larger, more complex parts. The witness specimen (15 mm cylinder) allows clear identification of layered stop-start flaws, at a resolution better than a complex part built alongside it, allowing to identify defective builds. The results indicate a successful first step at standardized microCT analysis procedures for improvement of processes and quality control in additive manufacturing.