CMAS-resistant environmental barrier coating system

An article comprising:

• a substrate;
• a first environmental barrier coating (EBC) layer on the substrate, wherein the first EBC layer comprises a rare-earth disilicate (REDS);
• a second EBC layer on the substrate, wherein the second EBC layer comprises the REDS, and wherein the second EBC layer defines a surface and a plurality of vertical cracks extending from the surface into the second EBC layer;
• and
• a CMAS-resistant EBC layer on the surface of the second EBC layer, wherein the CMAS-resistant EBC layer comprises at least one rare-earth monosilicate (REMS) configured to react with CMAS to form at least one crystalline reaction product, wherein a porosity of the CMAS-resistant EBC layer is less than about 15 volume percent, wherein the CMAS-resistant EBC does not include vertical cracks extending into a surface of the CMAS-resistant EBC,
• wherein the first EBC layer and the second EBC layer each include the REMS, and
• wherein the first EBC layer has a lower REMS/REDS composition ratio than a REMS/REDS composition ratio of the second EBC layer.

An article comprising:

• a substrate;
• a first environmental barrier coating (EBC) layer on the substrate, wherein the first EBC layer comprises a rare-earth disilicate (REDS);
• a second EBC layer on the substrate, wherein the second EBC layer comprises at least one of a rare-earth monosilicate (REMS) or REDS, and wherein the second EBC layer defines a surface and a plurality of vertical cracks extending from the surface into the second EBC layer;
• and
• a CMAS-resistant EBC layer on the surface of the second EBC layer, wherein the CMAS-resistant EBC layer comprises at least one of a REMS or REDS, wherein the CMAS-resistant EBC does not include vertical cracks extending into a surface of the CMAS-resistant EBC.