What aspects should be considered in the process evaluation of surfacing?

The key is to reduce the dilution rate of the transition layer in order to maintain the chemical composition of the weld metal in the surfacing layer; if the dilution rate is not properly controlled, cracks may appear at the interface between the surfacing layer and the base material under mechanical stress

The key lies in the welding of the transition layer, as it determines whether the subsequent bending test will be successful. It is necessary to use welding materials with a composition higher than that of the surface layer material, mainly due to the dilution rate, which affects whether the chemical composition of the weld metal in the cladded layer will meet the required standards.

The process evaluation for surfacing shall include at least: chemical analysis of the surface layer, penetrant testing, and bend test; optionally, the measurement of Vickers hardness of the surfacing layer, weld line, and heat-affected zone of the base material may be used as additional reference items. Requirements for surface chemical analysis: Samples shall be taken from the weld thickness specified in the drawing up to 2 mm downward for chemical analysis, and the results shall meet the requirements specified in the design documents. The requirements for penetrant testing shall be in accordance with Chapter 12 of JB4730 for penetrant testing of the surfacing. Requirements for the bending test: Take two bending specimens parallel to the surfacing weld direction, and two in the perpendicular direction, or four specimens all perpendicular to the weld direction.