TWI Core Research Programme Project 1153/2021
TWI undertook a Core Research Programme project to generate informative data for the selection of suitable inspection techniques for the testing of austenitic stainless steel welds. This case study presents the scope and activities of the project as well as subsequent follow-on work.
Austenitic stainless steel (SS), duplex stainless steel (DSS) and nickel alloy (NA) welds and cladding are increasingly being used in the oil and gas, power and petrochemical sectors, and in desalination equipment and wastewater treatment facilities.
Ultrasonic techniques are commonly used for non-destructive testing (NDT) of these materials, as they provide volumetric coverage and are able to interrogate large component thicknesses and complex geometries which preclude radiographic techniques. However, the welds typically display an austenitic structure, which consists of textured large grains, and this results in high ultrasonic scattering associated with mode conversion effects, beam distortion and a variation of ultrasound velocity with direction and position in the weld. Therefore, extensive parametric analysis is required to identify best practice inspection methods for such materials and welds.
It is known that welding procedures, geometry and position are known to have a strong influence on the inspection capabilities of ultrasonic methods. Quantifying the influence of these parameters on the performance of the ultrasound gives an advantage to inspection engineers and asset managers, in terms of selecting suitable inspection techniques and anticipating inspection performance more efficiently. It also reduces the requirement for representative demonstration mock-ups.