Evaluation of X-ray computed tomography for surface texture measurements using a prototype additively manufactured reference standard

Abstract

Additively manufactured (AM) components have complex surface textures compared with conventionally machined surfaces. There is an increasing demand from AM industry for reference standards to calibrate instruments for AM surface inspection; this is particularly important in application areas such as aerospace, where the failure of a mission-critical part can have dire safety consequences. Many AM surfaces have re-entrant features and internal surfaces and, therefore, are difficult or impossible to be accessed by conventional measurement techniques. X-ray computed tomography (XCT) is an emerging technology that is capable of measuring AM surfaces. However, the metrology framework of the technology is still under development. Recently, we have explored the calibration of XCT for surface texture evaluation using a reference standard with a unique design. The prototype surface texture reference standard has surfaces with varying roughness levels and has been designed for compatibility between profile and areal topography measuring instruments and tomography instruments. The measurement traceability of surface texture using XCT has been established for profile measurements via a calibrated contact measurement technique. This paper has further investigated the impact of sampling strategy in calibration. This preliminary study is to investigate the ability of XCT to evaluate the AM surface texture in different build orientations, where the surfaces may have limited evaluation length.