Is the word graves the same in Brazilian and European Portuguese?

Yes

The word "graves" is identical in spelling, meaning, and grammar in both Brazilian and Continental Portuguese. The only difference lies in pronunciation:

• Vowels: In Brazilian Portuguese, the unstressed "e" is typically pronounced as a closed "i" ([ˈɡɾaviːs]). In Continental Portuguese, the "e" is a reduced, near-silent neutral vowel ([ˈɡɾɐvɨʃ]).
• Sibilants: In most regions of Brazil, the "s" at the end of the word is pronounced as a sharp "s" ([s]). In Portugal, the "s" is pronounced as a "sh" sound ([ʃ]).

Brazilian Portuguese Examples

1. Os problemas graves da empresa estão incomodando. (The serious problems at the company are bothering [us].)
2. Ele cometeu erros graves na prova. (He made serious mistakes on the test.)
3. As notícias graves deixaram a galera preocupada. (The serious news left the folks worried.)
4. O som do carro tem graves muito fortes. (The car sound has very strong bass.)
5. Existem riscos graves para a saúde. (There are serious risks to health.)

Continental Portuguese Examples

1. Os problemas graves da empresa estão a incomodar. (The serious problems at the company are bothering [us].)
2. Ele cometeu erros graves no exame. (He made serious mistakes on the exam.)
3. As notícias graves deixaram a malta preocupada. (The serious news left the folks/group worried.)
4. O som do rádio tem graves muito potentes. (The radio sound has very powerful bass.)
5. Há riscos graves para a saúde. (There are serious risks to health.)