**2. Condition assessment of the material of welded joints in components operated beyond the design time by non-destructive methods**

The criterial element deciding about the suitability for further service of butt-welded joints of components operating under creep conditions is the exhaustion degree of basic materials determined based on the revealed state of microstructure and its determined class as well as the degree of internal damages and the class of damages of the heat-affected zone (HAZ) and weld material. The example of the results of non-destructive tests on microstructure of the primary

#### **Figure 2.**

*Assessment of the material condition with regard to changes in the structure and occurred internal damages caused by creep of parent material and circumferential welded joints in the vertical section of the primary steam pipeline made of 14MoV6-3 steel after approximately 220,000 h service (matrix replicas, SEM).*

steam pipeline components after long-term service under creep conditions far beyond the design service time without internal damages caused by creep is shown in **Figure 1**, while those with disclosed damages in the form of voids both in the basic material and in the heat-affected zone and weld material are shown in **Figure 2**. The results of these tests allow to take decisions whether the test pipelines can be left and only some of its components need to be replaced using the joining technology by welding materials with significant changes in microstructure caused by creep with new materials.

The assessment of the exhaustion degree and the degree of internal damages in the material of welded joint components allows for determination of the residual and disposable life of the welded joint, capability of the materials of welded joint components to make a possible repair to the test joint, capability of the test basic materials to produce a repair (old/old material) or modernisation (old/new material) welded joint and propose the appropriate welding technology.

To ensure that the condition assessment of the material of welded joint components after long-term service under creep conditions by non-destructive methods is accurate and the estimated exhaustion degree is reliable, the results of destructive materials testing of these components are required. The results of these tests should allow the assignment of exhaustion degree to determined degrees of microstructural degradation of such joints.

The material for destructive materials testing is selected based on the results obtained by non-destructive method of matrix replicas, which determine the class of microstructure and the estimated exhaustion degree for parent material and the class of damage for butt components of welded joints. The material for destructive testing in the form of a test specimen of the component with butt-welded joint is taken from the areas with the highest exhaustion degree and adopted as representative for the component or installation.
