Metallographic and Extraction Replica Methods for Characterization of Tungsten Heavy Alloy: H13 Clads

Tungsten heavy alloys are utilized in high-pressure die casting applications due to their exceptional strength, thermal conductivity, and minimal thermal expansion. However, the high cost restricts their use to small sintered die inserts and manual gas tungsten arc weld repairs. This study introduces Anviloy wire, a new tungsten heavy alloy consumable developed for the automated cladding of hot work tool steel dies. A deficit in literature on characterizing tungsten heavy alloy die steel clads prompted this research. Investigating the dilution effect of the base metal on clad microstructure necessitated the development of new sample preparation techniques. An Anviloy wire-H13 clad was produced via hot wire gas tungsten arc cladding and examined using metallography. The analysis revealed the presence of an M6C carbide phase along the grain boundaries of the as-welded samples, identified through the use of an alkaline sodium picrate etchant. Additionally, isothermally aged samples at 725°C for 100 hours were characterized with metallography, scanning electron microscopy, and transmission electron diffraction, which demonstrated a high volume fraction of intermetallic platelets. A novel carbon extraction replica method combining two chemical polishing steps was utilized, confirming the presence of mu phase intermetallics in the precipitates through transmission electron diffraction.