DIAMOND FILMS ON STAINLESS STEEL SUBSTRATES WITH AN ...
DIAMOND FILMS ON STAINLESS STEEL SUBSTRATES WITH AN INTERLAYER APPLIED BY LASER CLADDING A. Contin1*; K. A. Alves1; E. J. Corat1; V. J. Trava-Airoldi 1; G. Vasconcelos2 INPE, Instituto Nacional de Pesquisas Espaciais, LAS, CEP 12227-010, São José dos Campos, SP, Brasil 2 IEAv, Instituto de Estudos Avançados, dedALO, CEP 12228-001, São José dos Campos, SP, Brasil 1
The objective of this work is the Chemical Vapor Deposition (CVD) of diamond films on stainless steel substrates using a new technique for intermediate barrier forming, made by laser cladding process. In this technique, a thin layer of powder is irradiated and melted by a laser beam in order to melt the powder layer and the surface layer of the substrate to create the coating. The diamond’s deposition was performed using Hot-Filament CVD reactor and the characterization is accomplished by Scanning Electron Microscopy, X-ray diffraction, Raman Scattering Spectroscopy and scratch test.
Keywords: CVD diamond film, steel, laser cladding, interlayer
Introduction The use of CVD diamond films on steel substrates is an application of great interest due to their unique properties. The use of CVD diamond film as a protective film produces an increase in surface hardness, thermal conductivity and reduced friction and, thus, better corrosion protection. Direct synthesis of diamond films on steels has been limited due at least three major obstacles [1]. First, iron has some specific interactions with carbon during diamond deposition, growing a graphite layer on the surface. Second, the carbon from the gas phase has high diffusion rate into the steel at CVD temperatures, decreasing diamond nucleation on the surface. Third, the stainless steel has a higher thermal expansion coefficient than the diamond, resulting in a mismatch. These issues create the poor adhesion between diamond film and substrate. Therefore, it is necessary to create an intermediate layer for diamond film deposition on steel. Experimental part 304 Stainless steel disks with of 25.4 mm x 3 mm (diameter x thickness) were used as substrate for diamond coating. The powder used to create an intermediate layer was silicon carbide (SiC). The radiation source for laser cladding was a carbon dioxide laser. For diamond film deposition used an HFCVD (Hot Filament Chemical Vapor Deposition) reactor. During the deposition, the substrate was kept at controlled temperatures from 630 ºC. The adhesion of silicon carbide layer on the surface of substrate was evaluated by scratch test. X-ray Diffraction (XRD) was used for quantitative analysis of phases in the laser cladding process. Samples were characterized by Scanning Electron Microscopy (SEM) for qualitative analysis. Diamond film compressive residual stresses were analyzed by Raman Scattering Spectroscopy (RSS).
Results and discussion
Figure 1 shows the SEM image of the cross section of the sample after laser cladding process. It can be noted the formation of an intermediate layer of sintered SiC with a granular structure on surface of stainless steel substrate. The morphology of nanocrystalline diamond film grown on stainless steel is shown in the Figure 2. The efficiency of diffusion process blocking is evidenced by the diamond growth.
Steel SiC
Fig. 1 – Scanning electron microscopy
Fig. 2 – SEM micrograph of diamond
(SEM) micrograph of cross section of stainless steel after laser cladding process
film deposited on stainless steel after laser cladding process
Conclusions In this work, we created a new technique of intermediate barrier for diamond deposition on steel substrates. The interlayer, made by laser cladding, blocked the diffusion of iron to the surface of the substrate and carbon from the gas phase into the steel during the deposition of CVD diamond. Furthermore, the silicon carbide layer behaved as a bind layer, with intermediate mechanical and thermal properties between steel and the diamond, this fact minimizes the three main adherence problems between diamond film and steel substrate.
References [1] Li, Y.S., Tanga, Y., Yang, Q., XIAO, C., Hirose, A., 2010a. Growth and adhesion failure of diamond thin films deposited on stainless steel with ultra-thin dual metal interlayers. Applied Surface Science. Res. 256, 7653 – 7657.
Acknowledgement: The authors would like to thank FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo) for financial support of this work.
The objective of this work is the Chemical Vapor Deposition (CVD) of diamond films on stainless steel substrates using a new technique for intermediate barrier forming, made by laser cladding process. In this technique, a thin layer of powder is irradiated and melted by a laser beam in order to melt the powder layer and the surface layer of the substrate to create the coating. The diamond’s deposition was performed using Hot-Filament CVD reactor and the characterization is accomplished by Scanning Electron Microscopy, X-ray diffraction, Raman Scattering Spectroscopy and scratch test.
Keywords: CVD diamond film, steel, laser cladding, interlayer
Introduction The use of CVD diamond films on steel substrates is an application of great interest due to their unique properties. The use of CVD diamond film as a protective film produces an increase in surface hardness, thermal conductivity and reduced friction and, thus, better corrosion protection. Direct synthesis of diamond films on steels has been limited due at least three major obstacles [1]. First, iron has some specific interactions with carbon during diamond deposition, growing a graphite layer on the surface. Second, the carbon from the gas phase has high diffusion rate into the steel at CVD temperatures, decreasing diamond nucleation on the surface. Third, the stainless steel has a higher thermal expansion coefficient than the diamond, resulting in a mismatch. These issues create the poor adhesion between diamond film and substrate. Therefore, it is necessary to create an intermediate layer for diamond film deposition on steel. Experimental part 304 Stainless steel disks with of 25.4 mm x 3 mm (diameter x thickness) were used as substrate for diamond coating. The powder used to create an intermediate layer was silicon carbide (SiC). The radiation source for laser cladding was a carbon dioxide laser. For diamond film deposition used an HFCVD (Hot Filament Chemical Vapor Deposition) reactor. During the deposition, the substrate was kept at controlled temperatures from 630 ºC. The adhesion of silicon carbide layer on the surface of substrate was evaluated by scratch test. X-ray Diffraction (XRD) was used for quantitative analysis of phases in the laser cladding process. Samples were characterized by Scanning Electron Microscopy (SEM) for qualitative analysis. Diamond film compressive residual stresses were analyzed by Raman Scattering Spectroscopy (RSS).
Results and discussion
Figure 1 shows the SEM image of the cross section of the sample after laser cladding process. It can be noted the formation of an intermediate layer of sintered SiC with a granular structure on surface of stainless steel substrate. The morphology of nanocrystalline diamond film grown on stainless steel is shown in the Figure 2. The efficiency of diffusion process blocking is evidenced by the diamond growth.
Steel SiC
Fig. 1 – Scanning electron microscopy
Fig. 2 – SEM micrograph of diamond
(SEM) micrograph of cross section of stainless steel after laser cladding process
film deposited on stainless steel after laser cladding process
Conclusions In this work, we created a new technique of intermediate barrier for diamond deposition on steel substrates. The interlayer, made by laser cladding, blocked the diffusion of iron to the surface of the substrate and carbon from the gas phase into the steel during the deposition of CVD diamond. Furthermore, the silicon carbide layer behaved as a bind layer, with intermediate mechanical and thermal properties between steel and the diamond, this fact minimizes the three main adherence problems between diamond film and steel substrate.
References [1] Li, Y.S., Tanga, Y., Yang, Q., XIAO, C., Hirose, A., 2010a. Growth and adhesion failure of diamond thin films deposited on stainless steel with ultra-thin dual metal interlayers. Applied Surface Science. Res. 256, 7653 – 7657.
Acknowledgement: The authors would like to thank FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo) for financial support of this work.
