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Mishra B.,Colorado School of Mines | Moore J.J.,Goya Inc
Materials Science Forum | Year: 2010

High power pulsed magnetron sputtering (HPPMS) is an emerging thin film deposition technology that generate high ionization plasma by applying a very large amount of peak power to a sputtering target for a short period of time. HPPMS is also known as High Power Impulse Magnetron Sputtering (HiPIMS). However, HPPMS/HiPIMS exhibits decreased deposition rate as compared to continuous dc magnetron sputtering. Modulated pulse power (MPP) magnetron sputtering is an alternative HPPIMS deposition technique that overcomes the rate loss problem while still achieving a high degree of ionization of the sputtered material. In the present work, the principles and some important characteristics of MPP technology were presented. Technical examples of CrN coatings were deposited using MPP and continuous dc sources. The positive ion mass distributions were characterized using an electrostatic quadrupole plasma mass spectrometer. The structure and properties of MPP and dc CrN coatings were characterized using x-ray diffraction, scanning electron microscopy, nanoindentation tests, and ball-on-disc wear test. It was found that the MPP CrN coating exhibits denser microstructure and improved mechanical and tribological properties as compared to the dc CrN coating. © (2010) Trans Tech Publications. Source

Lin J.,Colorado School of Mines | Sproul W.D.,Colorado School of Mines | Sproul W.D.,Goya Inc | Moore J.J.,Colorado School of Mines | And 2 more authors.
Surface and Coatings Technology | Year: 2011

As a variation of high power pulsed magnetron sputtering technique, modulated pulse power (MPP) magnetron sputtering can achieve a high deposition rate while at the same time achieving a high degree of ionization of the sputtered material with low ion energies. These advantages of the MPP technique can be utilized to obtain dense coatings with a small incorporation of the residual stress and defect density for the thick coating growth. In this study, the MPP technique has been utilized to reactively deposit thick Cr2N and CrN coatings (up to 55μm) on AISI 440C steel and cemented carbide substrates in a closed field unbalanced magnetron sputtering system. High deposition rates of 15 and 10 μm per hour have been measured for the Cr2N and CrN coating depositions, respectively, using a 3kW average target power (16.7W/cm2 average target power density), a 50mm substrate to target distance and an Ar/N2 gas flow ratio of 3:1 and 1:1. The CrN coatings showed a denser microstructure than the Cr2N coatings, whereas the Cr2N coatings exhibited a smaller grain size and surface roughness than those of the CrN coatings for the same coating thickness. The compressive residual stresses in the CrN and Cr2N coatings increased as the coating thickness increased to 30μm and 20μm, respectively, but for thicker coatings, the stress gradually decreased as the coating thickness increased. The CrN coatings exhibited an increase in the scratch test critical load as the thickness was increased. Both CrN and Cr2N coatings showed a decrease in the hardness and an increase in the sliding coefficient of friction as the coating thickness increased from 2.5 to 55μm. However, the wear rate of the CrN coatings decreased significantly as the coating thickness was increased to 10μm or higher. The 10-55μm CrN coating exhibited low wear rates in the range of 3.5-5×10-7mm-N-1m-1. To the contrary, the Cr2N coating exhibited relatively low wear resistance in that high wear rates in the range of 3.5 to 7.5×10-6mm3N-1m-1 were observed for different thicknesses. © 2010. Source

Lin J.,Colorado School of Mines | Sproul W.D.,Colorado School of Mines | Sproul W.D.,Goya Inc | Moore J.J.,Colorado School of Mines
Surface and Coatings Technology | Year: 2012

Thick CrN coatings (up to 55μm) have been deposited on different substrate materials (WC-Co, M2 steel, AISI 440C steel, AISI 304 steel, Al-Si eutectic alloy, and copper) using the modulated pulsed power (MPP) magnetron sputtering technique at a high deposition rate of 10μm/h. The thick CrN coatings have been characterized for the microstructure, mechanical and tribological properties. The adhesion of the coatings with different thicknesses on different substrates was evaluated using progressive scratch tests. The dry sliding wear tests for the thick coatings deposited on the AISI 440C substrate were carried out using a ball-on-disk microtribometer. The wear tests were conducted on the 20μm thick MPP CrN coatings using different ball materials (α-Al 2O 3, WC-Co, AISI 440C steel, AISI 302 steel, 100Cr6 steel, and brass), different applied loads (5-40N) and sliding speeds (5-50cm/s) for a maximum sliding distance up to 10km. The coating wear tracks and ball wear scars were examined using scanning electron microscopy. The thick CrN coatings showed coefficients of friction in the range of 0.48-0.94 as sliding against different materials and under different test conditions. The wear rate of the coatings increased with the increases in the applied load and sliding speed, which is related to an increase in the plowing force (plastic deformation of the substrate) and an increase in the flash temperature, respectively. The wear rates of the 20μm thick MPP CrN coating are in the range of 1×10 -7 to 5.5×10 -7mm 3N -1m -1. This study has demonstrated that thicker CrN coatings exhibited larger load and sliding speed capacities, which allow them to be operated under more severe conditions, e.g. higher loads, sliding speeds, and operating temperatures. © 2011. Source

Lin J.,Colorado School of Mines | Moore J.J.,Colorado School of Mines | Mishra B.,Colorado School of Mines | Pinkas M.,Nuclear Research Center - Negev | And 2 more authors.
Acta Materialia | Year: 2010

TiBCN nanocomposite coatings were deposited in a closed field unbalanced magnetron sputtering system using pulsed magnetron sputtering of a TiBC compound target with various Ar/N2 mixtures. TiBCN coatings were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, nanoindentation, Rockwell C indentation and ball-on-disk wear tests. The coatings with a nitrogen content of less than 8 at.% exhibited superhardness values in the range of 44-49 GPa, but also showed poor adhesion and low wear resistance. Improvements in the coating adhesion, H/E ratio and wear resistance were achieved together with a decrease in the coating hardness to 35-45 GPa as the N content in the coatings was increased from 8 to 15 at.%. The microstructure of the coatings changed from a nano-columnar to a nanocomposite structure in which 5-8 nm nanocrystalline Ti(B,C) and Ti(N,C) compounds were embedded in an amorphous matrix consisting of BN, free carbon and CN phases. With a further increase in the N content in the coatings to levels greater than 20 at.%, the inter-particle spacing of the nanocrystalline compounds increased significantly due to the formation of a large amount of the amorphous BN phase, which also led to low hardness and poor wear resistance of the TiBCN coatings. Source

Goya Inc | Date: 2016-02-02

Processed grains; Processed quinoa; Rice.

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