The Biggest Risk Visit weldfabworld.com 1. Prevention of Cracking (Most Critical) The primary reason engineers require hardness testing is to avoid Hydrogen Induced Cold Cracking (HICC). Hardness vs. Brittleness: When a weld cools rapidly, it can form a very hard but brittle microstructure called Martensite. The "Trap": If the hardness is too high, hydrogen (from moisture or contaminants) gets trapped in these brittle areas. Under stress, this leads to sudden, delayed cracking. Control: Industry