Comportamento tribológico do aço inoxidável martensítico CA-6NM nitretado por plasma em ensaio de riscamento linear

Abstract

Resumo: Tratamentos de superficies, tais como a nitretacao por plasma tem sido amplamente utilizado em diversas aplicacoes industriais, pois melhoram consideravelmente as propriedades mecanicas, tribologicas e quimicas dos materiais. Este trabalho aborda a utilizacao do processo de nitretacao por plasma a baixa temperatura no aco inoxidavel martensitico CA-6NM, visando a melhoria das propriedades tribologicas por riscamento linear. As amostras foram nitretadas com temperaturas de 300, 350 e 400 °C em periodos de tratamentos de 6, 12 e 24 horas, com fluxo gasoso de 300sccm, mistura gasosa de 5%N2 + 95%H2 a uma pressao de 4,0 Torr. As camadas tratadas foram caracterizadas por microscopia otica, difracao de Raios-X, medidas de microdureza, nanodureza e rugosidade, alem do ensaio de desgaste utilizando o tribometro na configuracao de riscamento linear, com carga constante de 4 e 8 N com indentador de diamante. Melhoras acentuadas no comportamento tribologico das amostras nitretadas por plasma sao observadas quando comparadas com as propriedades do material original nao nitretado.

Abstract: Surface treatments such as plasma nitriding have been widely used in various industrial applications because they significantly improve the mechanical, tribological and chemical properties of materials. This work discusses in terms of the linear scratch test the use of plasma nitriding performed at low temperatures in the martensitic stainless steel CA-6NM, aiming to improve its tribological properties. Samples were nitrided at temperatures of 300, 350 and 400 °C for periods of treatments of 6, 12 and 24 hours, with gas flow rate of 300 sccm, gas mixture composition of 5%N2 + 95%H2, at a pressure of 4 Torr. The treated layers were characterized by optical microscopy, (XRD) X-rays diffraction, hardness, nanohardness and roughness measurements, in addition to wear test using the tribometer in the scratch test configuration, with two different constant loads, constant loads 4 and 8 N and diamond indenter. Improved tribological properties were obtained for the plasma nitrided surfaces when confronted with those verified for the non-treated original substrates.