Mold wear during permanent-mold casting of Ti-6Al-4V

Mold wear during the casting of Ti-6Al-4V in a permanent (steel) mold was investigated using a combination of macro- and micro-scale observations and measurements. For this purpose, a steel mold with interchangeable inserts of three candidate mold steels (H13, P20, and 1040) was used. Inserts were removed at regular intervals during casting under prototype-production conditions and inspected to assess mold wear. Two major mold wear types were identified: soldering and “wrinkling.” Soldering was concluded to be a result of local over-heating of the mold, and wrinkling a result of cyclic stresses caused by a combination of solid-state phase transformations and large temperature gradients. The 1040 inserts performed the best; soldering was less severe and wrinkling did not occur. The better performance of the 1040 inserts was attributed to lower mold temperatures and thermal gradients due to the higher thermal conductivity of 1040 relative to H13 or P20.