Nodularity Control of Spheroid Ductile Cast Iron by Rayleigh Backscattering

Spheroid Ductile Cast Iron finds increasingly industrial use as a high strength material of high fatigue resistance. The material properties can be designed by density, shape and size of the graphite spheres—the nodularity—and the matrix microstructure. Until today, the near surface nodularity cannot be controlled nondestructively to take full advantage of the material quality especially at high loaded surface areas. A viable nondestructive approach we propose is based on ultrasonic backscattering preferably in the Rayleigh regime. First experiments with model samples proved significant contrast to distinguish materials with different graphite morphology and matrices. The claim of our tests is a fast and easy industrial control of nodularity in reference to a validated sample. The results encourage us for the development of a prototype equipment with optimized probe systems and inspection parameters. Quantified acceptance criteria still require systematic tests for optimized parameter settings and probe configurations on more representative samples provided by industry.