The Effects Of Substrate-To-Target Distance On Properties And Microstructures Of The Carbon/Chromium Composite Coatings

There is a biggish working chamber in closed-field unbalanced magnetron sputtering deposition system, and it's very possible for substrate-placed position to affect the quality of coatings markedly. At present, correlative investigations are all focus on the effect of substrate-placed position on thickness of coatings, this problem need a comprehensive and in-depth research yet. The carbon/chromium composite coatings were deposited on M2 high speed steel using a Britainic Teer UDP450 unbalanced magnetron sputtering deposition system, these coatings had been deposited at different substrate-placed position and the others deposition parameters are same. The thickness of coatings were measured using a Teer BC-1 ball crater device, the micro-hardness of coatings were measured using a Fischerscope HVS-1000 micro-hardness tester, the adhesion of coatings were measured using a Teer ST2200 scratch tester , and the tribological properties of coatings were measured using a Teer POD-1 pin-on-disc tester. The microstructures of the coatings were observed and analyzed using scan electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and Raman spectra. Furthermore, the distribution of magnetic field in the working chamber was characterized using Model 6010 Hall Effect Gauss/Tesla-Meter. The effects of substrate-to-target distance on properties and microstructures of the coatings were investigated, and the mechanisms about these effects were also discussed in this paper.The investigative results indicated that the carbon/chromium composite coatings be deposited in this paper are mostly amorphous material, the effects of substrate-to-target distance on properties and microstructures of the coatings are great, and the effects caused by substrate-to-target radial distance are stronger markedly than that caused by substrate-to-target axial distance. With the increasing of substrate-to-target radial distance, the thickness of coatings are decreased, the micro-hardness of coatings are increased and then are decreased, the adhesion of coatings are increased and then are decreased, the friction coefficient of coatings are increased and then are decreased, the wear rate of coatings are increased and then are decreased, surface morphology of coatings become rough and then become slick, and the sp2 content of coatings have a minimum value. With the substrate-to-target axial distance away from the center of working chamber, the thickness and sp2 content of coatings are decreased, the micro-hardness and friction coefficient of coatings are increased, the adhesion and wear rate of coatings are invariable approximately, surface morphology of coatings becomeslick appreciably. The uniform carbon/chromium composite coatings can be deposited in the range of the substrate-to-target radial distance from 70mm to 140mm or the substrate-to-target axial distance from -50mm to 50mm using UDP450 unbalanced magnetron sputtering deposition system. The essential reason creating the effects of substrate-to-target distance on properties and microstructures of the coatings is the dissimilitude of deposition particle current density and energy with the different substrate-placed position, and this dissimilitude was caused by three factors, viz. the asymmetric distribution of magnetic field in the working chamber of UDP450 system , the difference of scattering collision intensity of deposition particles during their movements at the different substrate-placed position and the difference of acceleration of deposition ion from the substrate negative bias voltage at the different substrate-placed position.