Papers

ICMCTF2002 Session B7-1: Plasma Assisted CVD, Thermochemical Treatments and Duplex Technology

Monday, April 22, 2002 1:30 PM in Room Golden West

Monday Afternoon

Start	Invited?	Item
1:30 PM		B7-1-1 High Plasma Density CVD, from Diamond to DLC O.K. Massler, J. Karner, D. Franz (Balzers AG, Liechtenstein) Carbon based films play an important role in industry, from the field of high hardness coatings for cutting tools over optics and electronics to coatings for tribological applications in mechanical engineering for wear protection and friction reduction. Crystalline diamond is the hardest material known. Films are produced effectively with a high density carbon-hydrogen. The resulting films can be varied in crystal size and surface structure by the process parameters. A very common way to use the superior properties of the diamond bonding is the formation of amorphous carbon based coatings by plasma CVD methods. Those coatings contain an amount of the diamond bonding in an amorphous network of carbon and hydrogen. The mechanism of this process is commonly the activation of the carbon based species in the plasma and the reaction on the surface, often supported by high bias voltages to create an additional stress in the film by an ion-impact on the surface. The resulting films do not contain a crystalline structure, but an amorphous network of carbon and hydrogen. Since the structure of the network can varied in a wide range, also the film properties can be varied in a wide range, like hardness, wear resistance and friction coefficient. An addition of various metals into the network further modifies the film properties, which can be used to tailor the surface energy or improve the interface between the film and the substrate. The formation of a graded interface is of particular importance for the adhesion between the substrate and the film. The process temperature of PACVD processes is significantly lower than the temperature of a pure CVD process and ranges between 150 and 250Â°C. This enables a wide variety of materials to be coated and a wide variety of new applications.
2:10 PM		B7-1-3 Duplex Surface Treatment of Chromium Pack Diffusion and Plasma Nitriding of Mild Steel V.H. Baggio-Scheid, G. Vasconcelos (Centro Tecnico Aeroespacial, Brazil); M.A.S. Oliveira, A.K. Viera (Instituto Tecnologico de Aeronautica, Brazil); A.C.S Santos (Metal Plasma, Brazil) The use of mild steel has been usually restricted to low cost applications of structural nature, because of their poor physical chemical properties. Recently, new duplex surface treatments involving the use of packing diffusion, electroplating and plasma nitriding give the possibility to use this material for applications which were usually typical for the tool steels. In this work we present results concerning the duplex treatment of chromium pack diffusion and plasma nitriding of AISI 1020 mild steel. The sample were chromizing in a vacuum furnance at temperatures varying from 900°C up to 1300°C for 5h. After the chromizing the samples were plasma nitrided for 1h. The nitriding temperatures were varied between 400°C and 500°C. The samples were characterized by SEM, EDS, XRD and microhardness tester. Chromium diffusion layers up to 150µm were obtained. The subsequent plasma nitriding increases the surface hardness up to 1400 HV (100gf) due to the formation of CrN and Cr₂N. The corrosion resistence of the chromized and duplex-treated specimens was also studied. The improvements in hardness and corrosion resistance are discussed considering the microstructural modifications in the treated sample.
2:30 PM		B7-1-4 Optical and Electrical Properties of BON and Multilayered TiN/BON Thin Films Prepared by PAMOCVD Method D.-C. Lim, G.C. Chen, S.-B. Lee, J.-H. Boo (Sungkyunkwan University, Korea) We have firstly grown the BON and multilayered TiN/BON thin films on Si(100) in the deposition temperature range RT¡500°C by low frequency R.F. derived plasma assisted MOCVD. trimethylborate(TMB) and Tetrakis dimethyl amido titanium(TDMAT) precursors were used to grow BON and multilayered TiN/BON thin films. N₂ and NH₃ gases as additional nitrogen source were used for reactive gases and the plasma source gases were Ar and H₂. The as-grown films were analyzed with XRD, XPS, RBS, FT-IR, UV, SEM, TEM, I-V/C-V characteristics, and Knoop microhardness tester. The effects of deposition time, substrate temperature and reaction gas on the hardness, electrical and optical property were mainly investigated in this study. FT-IR result shows that the bond type in the films is very similar to B-O-N and prefer to angular structure rather than linear one. UV results show that BON is semiconductor material with 3.4 eV of wide band gap. The I-V/C-V characte! ristics also show the BON thin films have semiconductor property. We found that the microhardness and optical properties of the as-grown thin films as well as optical properties were strongly dependent by nitrogen flux and growth time. Typically, the electrical resistance was decreased with increasing the nitrogen flux and growth time while the microhardness was increased with increasing the nitrogen contents in the film layers.
2:50 PM		B7-1-5 Deposition of Corrosion-resistant Films by an Atmospheric Pressure Glow Discharge (APG) R. Foest, F. Adler, M. Schmidt (Institute for Low Temperature Plasma Physics Greifswald, Germany) The deposition of thin silicon organic films on a technical Aluminum sheet metal in a homogeneous atmospheric pressure dielectric barrier discharge in helium with small admixtures (10^-4) of hexamethyldisiloxane (HMDSO) vapor and the study of this discharge is reported. Expensive vacuum technique is not required for atmospheric pressure treatment. Thus production costs are reduced. The powered (100 kHz) plane electrode (80x15 mm²) is covered by a glass insulator layer and is positioned above the grounded substrate holder which is movable over a larger area. To characterize the discharge in the gap of 1 to 3 mm power absorption, sustaining voltage, (V_pp ~ 2 kV), gap voltage, current density (j ~ 1 mA cm^-2), and total light emission are monitored. The gas composition of the exhaust gas is studied by mass spectrometry. During discharge operation a decrease of the precursor concentration is observed, due to dissociation and thin film deposition. Typical deposition rates range about 10^-7 g cm^-2 s^-1, as measured by substrate weighing. Inspection of the film by optical and scanning electron microscopy shows a plane surface without significant structures. The films display water contact angles of 65-70°. A corrosion resistance against 0.1n-NaOH of 3 min is observed. FT-IR (dominant SiOSi band) and XPS (low C content) spectra both reveal the non-organic nature of the film. The electron concentration is experimentally determined by heterodyne interferometry. Using these results thin film deposition and discharge properties are discussed in relation to the ionization rate of the precursor molecules and the current density.
3:50 PM		B7-1-8 Wear and Adhesion of Plasma Nitrided and Magnetron Sputtered Coating on Three-dimensional Object. J. Haider, M.S.J. Hashmi (Dublin City University, Ireland) The number of different coating procesesand coating systems is rapidly increasing in the surface engineering technology. Duplex treatment is relatively new term in surface engineering. Low alloy steel substrate and hard PVD coating have huge difference in hardness. Plasma nitriding of the low-alloy steel will decrease the hardness and stress gradient between the coating and substrate providing a better adhesion of the hard coating. In this paper we will present results obtained with duplex coating of an in-situ plasma nitriding followed by magnetron sputtering with TiN and TiAlN on flat and three dimensional substrate.
4:10 PM		B7-1-9 Effect of Heat Treatment on the Mechanical Properties of Ion-Plated TiN Film W.-J. Chou, G.P. Yu, J.-H. Huang (National Tsing Hua University, Taiwan, ROC) Heat treatment processes were widely applied to improve the properties of hard coatings. However, the mechanisms that enhance thin film properties are still unclear. In this study, titanium nitride (TiN) films were deposited on 304 stainless steel using a hollow cathode discharge ion-plating (HCD-IP) technique. A novel heat treatment process capable of detecting and controlling oxygen partial pressure down to 10^-26 Torr was employed to reduce the oxidation of the thin films. The residual stress and preferred orientation of TiN films were determined using X-ray diffraction (XRD). Hardness of the films was measured by nanoindentation. Atomic force microscopy (AFM) was used to study the surface roughness of thin film. The experimental results show that the (111) texture coefficient increased with increasing treatment temperature. The hardness of TiN films rapidly increased 10%~40% after heat treatment process. The residual stress ranged from -5.5 to -7 GPa, depending on different deposition conditions, after heat treatment at 400°C for 1 hour; while after heat treatment at 700°C the residual stress was reduced to about -3.45 GPa. Hardness enhancement mechanism was different in 400°C and 700°C process, and can be related to the residual stress in the film. The mechanisms of TiN film hardness improvement after heat treatment were discussed in this study.
4:30 PM		B7-1-10 Effect of Grain Orientation on the Nitriding Rate of a Nickel Base Alloy Studied by Electron Backscatter Diffraction (EBSD) H. He, T. Czerwiec, H. Michel (Ecole des Mines, France); C. Dong (Dalian University of Technology, China, PR) Inconel 690 is a nickel base alloy (57 at.% Ni, 32 at.% Cr, 10 at.% Fe, 0.7 at.% Si and 0.3 at.% Mn) with a broad range of potential applications, for instance in aerospace, navy and marine industries as well as nuclear reactor technology^[1]. A low temperature Plasma Assisted Nitriding (PAN) treatment is expected to improve the tribological properties without changing the corrosion resistance of this alloy. As it is well known for austenitic stainless steels, such a treatment of Inconel 690 leads to the formation of a metastable supersaturated f.c.c. nitrogen solid solution usually called expanded austenite, S phase, m phase or N phase^[2]. However, the studied nickel base alloy presents variations in the layer thickness from grains to grains. Electron Backscatter Diffraction (EBSD) is a rather new and powerful technique which provides local orientation of crystals. The aim of this paper is to present the results we get on the cross-section of Inconel 690 nitrided samples. We have found a linear relationship between the thickness of the nitrided layer and γmin<100> (the minimum included angle between the <1 0 0> crystal direction of a grain and the nitriding direction). The <1 0 0> oriented grains are associated to thicker diffusion layers as compared to the <1 1 1> oriented grains. ^[1] C. Rives, T. Czerwiec, T. Belmonte, F. Belnet, H. Michel, O. Kerrec, Proc. of Icône 8, 8th Int. Conf. on Nuclear Engi., April 2-6, 2000, Baltimore USA, ed. by ASME. ^[2] T. Czerwiec, N. Renevier, H. Michel, Surf. Coat. Technol., 131 (2000) 267.
4:50 PM		B7-1-11 Nucleation and Growth of Iron Nitrides on the Surface of Pure Iron and Steels J. Oseguera (ITESM-CEM, Mexico); O. Salas (ITESM-CEM/Colorado School of Mines); J.L. Bernal, U. Figueroa (ITESM, Mexico) THIS WORK ENCOMPASSES A NUMBER OF STUDIES ON KINETICS AND MICROSTRUCTURAL EVOLUTION DURING NUCLEATION AND GROWTH OF NITRIDES ON THE SURFACE OF PURE IRON AND CARBON STEELS. THE RESULTS ARE ANALYZED AND COMPARED IN TERMS OF THE PROCESSING TECHNIQUE, ION NITRIDING VS. POST-DISCHARGE NITRIDING, AS WELL AS ON THE PROCESSING CONDITIONS. CHARACTERIZATION OF THE REACTIVE ATMOSPHERE BY OPTICAL EMISSION SPECTROSCOPY HAS PROVIDED USEFUL INFORMATION TO DEVELOP ANALYTICAL MODELS TO STUDY THE INITIAL STAGES OF NITRIDING. RESULTS FROM THESE MODELS ARE COMPARED TO EXPERIMENTAL RESULTS. .