**3. Condition assessment of the material of welded joints operated beyond the design time using destructive methods**

The destructive materials testing on long-time operated welded joints are carried out on homogeneous butt-welded joints of thick-walled components. Most often, these are welded joints of steam pipelines as well as steam superheater chambers and temperature controllers made of the following steel grades: 13CrMo4-5, 10CrMo9-10, 14MoV6-3, X20CrMoV121 and sometimes 15Mo3.

These tests include the observations of microstructure and hardness measurement of different areas of joints from parent material through heat-affected zone and weld. The simultaneous testing of mechanical properties and residual life of the welded joints and parent material are used to search for relations between the state of microstructure and these properties. It is also important to search for correlation between the mechanical properties, especially residual life, of the parent material and welded joint.

The characteristics created based on the obtained test results are used for assessing the condition and forecasting the further safe service of the parent material and welded joints operated beyond the design service time. Moreover, they are decisive in making decisions on the possibility of repairing welded joints using the materials after long-term service under creep conditions and developing the joining technologies.

**37**

**Figure 3.**

*Creep Characteristics of Engineering Materials DOI: http://dx.doi.org/10.5772/intechopen.86078*

**time under creep conditions**

**Figure 3** and summarised in **Table 1**.

**3.1 Structure assessment of the material of welded joints operated for a long** 

The selected example showing the state of structure of homogeneous buttwelded joints after long-term service compared to the structure of the parent material of a component after service far beyond the design service life is shown in

*Structure of the material of homogeneous butt-welded joint components of the main primary steam pipeline made of 14MoV6-3 steel after approximately 200,000 h service under creep conditions parent material marked* 

*PM1, PM2; weld material marked WELD heat-affected zone marked HAZ1, HAZ2.*

*Creep Characteristics of Engineering Materials DOI: http://dx.doi.org/10.5772/intechopen.86078*

*Creep Characteristics of Engineering Materials*

ture caused by creep with new materials.

tural degradation of such joints.

tive for the component or installation.

technology.

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 microstruc-

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

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 microstruc-

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 representa-

**3. Condition assessment of the material of welded joints operated** 

The destructive materials testing on long-time operated welded joints are carried out on homogeneous butt-welded joints of thick-walled components. Most often, these are welded joints of steam pipelines as well as steam superheater chambers and temperature controllers made of the following steel grades: 13CrMo4-5, 10CrMo9-10, 14MoV6-3, X20CrMoV121 and sometimes

These tests include the observations of microstructure and hardness measurement of different areas of joints from parent material through heat-affected zone and weld. The simultaneous testing of mechanical properties and residual life of the welded joints and parent material are used to search for relations between the state of microstructure and these properties. It is also important to search for correlation between the mechanical properties, especially residual life, of the parent material

The characteristics created based on the obtained test results are used for assessing the condition and forecasting the further safe service of the parent material and welded joints operated beyond the design service time. Moreover, they are decisive in making decisions on the possibility of repairing welded joints using the materials after long-term service under creep conditions and developing the joining

**beyond the design time using destructive methods**

**36**

15Mo3.

and welded joint.

technologies.
