When multifunctional surface engineering processes that combine purpose-oriented phases are applied to soft substrates, a combination of high wear resistance, high load support and low coefficients of friction can be achieved. In this study, the effects of different nitrided layers on the tribological behaviour of a diamond-like carbon (DLC) film deposited on a SAE 1040 steel were investigated. The nitriding was carried out under different temperatures and gas mixtures to create three distinct nitrided layers: two compound layers with predominant ε and γ' phases and a diffusion layer. All of the surfaces were then coated with DLC deposited via plasma-enhanced chemical vapour deposition (PECVD). The tribological tests indicated that the best performance was achieved for a specific combination of hardness, surface roughness and nitride type. The best load-bearing capacity between the DLC coating and the soft substrate was achieved when the nitrided layer was primarily a diffusion layer.

ResumoQuando processos de engenharia de superfícies multifuncionais que combinam fases de propósito orientadas são aplicados a substratos moles, uma combinação de alta resistência ao desgaste, suporte de alta carga e baixos coeficientes de atrito podem ser obtidos. Neste estudo, os efeitos de diferentes camadas nitretadas no comportamento tribológico de revestimento Diamond-Like-Carbon (DLC) depositado sobre aço SAE 1040 são investigados. A nitretação foi conduzida sob diferentes temperaturas e misturas de gases para criar três camadas de nitretos distintas: duas camadas de compostos com predominância de fases ε e γ' e uma camada de difusão. Todas as superfícies foram então revestidas com DLC, depositado via Plasma-Enhanced-Chemical-Vapour-Deposition (PACVD). As fases de nitreto foram analisadas utilizando difração de raios-X e a topografia da superfície foi analisada por interferometria de luz branca e microscopia eletrônica de varredura. O comportamento tribológico foi investigado utilizando esfera e plano com movimento alternado com carregamento incremental até a falha do filme DLC. Os testes tribológicos indicaram que o melhor desempenho foi alcançado por uma específica combinação de dureza, rugosidade superficial e tipo de nitreto. A melhor capacidade de mancalização entre o revestimento DLC e o substrato mole foi alcançada quando a camada de nitretos constitui-se apenas de uma camada de difusão. Palavras-chave: DLC; Nitretação; Rugosidade; Atrito; Adesão. EFFECTS OF DIFFERENT PLASMA NITRIDE LAYERS ON THE TRIBOLOGICAL PERFORMANCE OF DLC COATINGS AbstractWhen multifunctional surface engineering processes that combine purpose-oriented phases are applied to soft substrates, a combination of high wear resistance, high load support and low coefficients of friction can be achieved. In this study, the effects of different nitride layers on the tribological behaviour of a diamond-like carbon (DLC) film deposited on a SAE 1040 steel were investigated. The nitriding was carried out under different temperatures and gas mixtures to create three distinct nitride layers: two compound layers with predominant ε and ' phases and a diffusion layer. All of the surfaces were then coated with DLC deposited via plasma-enhanced chemical vapour deposition (PACVD). The nitride phases were analysed using X-ray diffraction, and the surface topography was analysed by white-light interferometry and scanning electron microscopy. The tribological behaviour was evaluated using a ball on a reciprocating plane with incremental loading until each DLC film failed. The tribological tests indicated that the best performance was achieved for a specific combination of hardness, surface roughness and nitride type. The best load-bearing capacity between the DLC coating and the soft substrate was achieved when the nitride layer was primarily a diffusion layer.

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