ESTUDO DO PERFIL DE CARBONO NA CAMADA NITRETADA DO AÇO AISI M2
A STUDY OF CARBON PROFILE IN THE NITRIDED LAYER OF AISI M2 STEEL
Tier, Marco Antônio D.; Kieckow, Flávio; Strohaecker, Telmo Roberto; Rocha, Alexandre da Silva; Santos, Jorge Fernandez dos; Bell, Thomas
http://dx.doi.org/10.4322/tmm.00402002
Tecnol. Metal. Mater., vol.4, n2, p.6-11, 2007
Resumo
O principal objetivo deste trabalho é investigar a redistribuição do carbono que normalmente se observa após a nitretação a plasma de aços. Amostras do aço AISI M2 foram nitretadas em um reator a plasma com 60 kW, variando-se temperatura, tempo e composição do gás de tratamento. Foram realizadas análises de difração de raios X, espectroscopia de emissão óptica em descarga incandescente – GDOS e microscopia óptica e eletrônica de varredura. De acordo com as análises GDOS, as amostras nitretadas apresentaram descarbonetação na superfície da camada nitretada, e enriquecimento de carbono na região de interface da camada com o substrato. Para algumas condições de tratamento, foi observada a existência de um pequeno pico de carbono na interface entre a camada de compostos e a zona de difusão. Os resultados obtidos sugerem que a camada de compostos atue como uma barreira para a descarbonetação. Observa-se que, em amostras com camada de compostos bem definidas, o nível de descar bonetação foi baixo resultando em uma significativa precipitação de carbetos em contornos de grão.
Palavras-chave
Nitretação a plasma, Camada nitretada, Descarbonetação
Abstract
The aim of this work is to investigate the redistribution of carbon normally observed after plasma nitriding of steels. Samples of AISI M2 steel were plasma nitrided in a 60 kW reactor varying temperature, time, and treatment gas composition. X-ray diffraction, glow discharge optical spectroscopy – GDOS, optical and scanning electron microscopy analysis were performed. According to GDOS analysis, the samples presented decarburization on the surface of the nitrided layer and a carbon enrichment zone in the interface layer-substrate. For some conditions of treatment, it was observed the presence of a small peak of carbon in the interface between the compound layer and the diffusion zone. The results suggest that the compound layer works as a barrier for the decarburization process. It was observed that for samples with a compact compound layer, the level of decarburization was low which resulted in a high level of carbides precipitation in the grain boundaries.
Keywords
Plasma nitriding, Nitrided layer, Decarburization
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