Part made of composite material, having controlled creep

A part made of coated composite material comprising:

• a substrate made of ceramic matrix composite material;
• a tie-coat layer covering the substrate;
• and
• a protective coating that is on the tie-coat layer and that defines at least one environmental barrier, the protective coating comprising at least one rare-earth silicate, which is selected from the group consisting of ytterbium disilicate (Yb2Si2O7), yttrium disilicate (Y2Si2O7) and any combination thereof, and comprising at least:
• a first outer region comprising an outer surface of the protective coating opposite to the substrate and having a first working creep, having deformation of less than or equal to 0.07% when a compressive stress of at least 50 MPa is applied for a duration of 10hours at a temperature of between 1050° C. and 1300° C., said first region comprising at least one grain growth inhibitor in a sufficient quantity to obtain this first creep;
• and
• a second, inner, environmental barrier region, comprising at least one interface of the protective coating with the tie-coat layer and having a second working creep, having deformation of at least 0.01% when a compressive stress of at least 50 MPa is applied for a duration of 10 hours at a temperature of between 900° C. and 1000° C.,
• wherein the grain growth inhibitor is selected from the group consisting of zirconium oxide (ZrO2), titanium oxide (TiO2) and hafnium oxide (HfO2) and any combination thereof, and
• wherein the content by mass of grain growth inhibitor in the first region is between 0.05% and 10%.