Looking for some feedback. We weld components together by laser welding. The welding components are made of CP Ti grade1, CP Ti grade2, CP Ti grade4, and Ti-6Al-4V alloy.  Titanium welds are very sensitive to contamination. The contamination of titanium welds by interstitial elements (such as Oxygen, Nitrogen, Carbon, and Hydrogen) reduces the ductility and increases hardness. Since our components are small, we do Knoop microhardness test on cross section sample to monitor the weld quality. We need to setup criteria for knoop microhardness test. Could you have any suggestion about how to setup a specification or guideline of the criteria? Thanks in advance.