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

Yes

The spelling, meaning, and grammatical function of "martelo" are identical in both Brazilian and Continental Portuguese. The only differences are phonological. In Brazilian Portuguese, the vowels are more open and clearly articulated. In Continental Portuguese, unstressed vowels undergo significant reduction; for example, the final "o" in "martelo" is often pronounced as a very short, nearly silent "u" sound, and the unstressed "e" may be almost swallowed.

Brazilian Portuguese Examples

1. Eu preciso de um martelo para pendurar esse quadro. (I need a hammer to hang this picture.)
2. Cuidado para não acertar o dedo com o martelo! (Be careful not to hit your finger with the hammer!)
3. O martelo está guardado na gaveta. (The hammer is kept in the drawer.)
4. Você pode me emprestar seu martelo? (Can you lend me your hammer?)
5. Ele usa o martelo para quebrar o entulho. (He uses the hammer to break the debris.)

Continental Portuguese Examples

1. Preciso de um martelo para pendurar este quadro. (I need a hammer to hang this picture.)
2. Tem cuidado para não te bateres o dedo com o martelo! (Be careful not to hit your finger with the hammer!)
3. O martelo está guardado na gaveta. (The hammer is kept in the drawer.)
4. Podes emprestar-me o teu martelo? (Can you lend me your hammer?)
5. Ele usa o martelo para partir o entulho. (He uses the hammer to break the debris.)