Volume 35, Issue 6 (November 2007)
Nondestructive Testing for the Integrity Evaluation of Erosive and Abrasive Boundary Layers
The test surfaces of erosion and abrasion specimens are prepared by electrical discharge machining, grinding, turning, and polishing. These machining operations form an affected material zone (AMZ), with mechanical and metallurgical alterations. As a result, the erosion properties of the AMZ vary from those of the base material, thereby affecting the cumulative mass loss-time curve. Erosion and abrasion standards loosely specify the preparation method of the specimens’ test surface and relate to the AMZ integrity in a qualitative way. Consequently, there is a large variation in the AMZ thickness and properties, and in the mass loss-time pattern. There are several nondestructive test (NDT) methods for determining subsurface integrity. These methods enable one to determine material isotropy, and hardness, residual stress, and grain size gradients in the subsurface layer of many materials. Applying NDT methods in inspection of erosion and abrasion specimens will enable one to conduct better controlled erosion and abrasion tests with high precision results.