Thermochemical degradation of HfSiO4 by molten CMAS

The thermochemical degradation of hafnium silicate (HfSiO4) was investigated with a molten calciummagnesium-aluminosilicate (CMAS) glass relevant to gas turbine engine applications. Sintered HfSiO4 coupons were fabricated, within which wells were drilled and filled with CMAS glass powder at a loading of ~35 mg/cm2. Samples were heat treated at 1200 degrees C, 1300 degrees C, 1400 degrees C, and 1500 degrees C for 1 h, 10 h, and 50 h. At 1200 degrees C and 1300 degrees C, slow formation of a Ca2HfSi4O12 cyclosilicate phase was observed at the HfSiO4-CMAS interface. At 1300 degrees C and higher, rapid infiltration of CMAS into the material along the grain boundaries was observed. Initial conjecture into CMAS degradation mechanisms of HfSiO4 are presented herein.

Automated summary

The thermochemical degradation of hafnium silicate (HfSiO4) was investigated with a molten calcium-magnesium-aluminosilicate (CMAS) glass. The formation of Ca2HfSi4O12 cyclosilicate phase at lower temperatures and rapid infiltration of CMAS into HfSiO4 at higher temperatures were observed.