Papers

ICMCTF1999 Session A2: Coatings to Resist Wear at High Temperatures

Monday, April 12, 1999 8:30 AM in Room Council/Chamber/Cabinet

Monday Morning

Start	Invited?	Item
10:30 AM		A2-7 High Temperature Particulate Erosion of Plasma Sprayed YSZ vs. Selected Powder Characteristics and Plasma Torch Designs H.E. Eaton (United Technologies Research Center); P. Zajchowski (Pratt & Whitney Aircraft) Particulate erosion behavior of plasma sprayed yttria stabilized zirconia (YSZ) is discussed versus YSZ powder characteristics and versus plasma spray torch design. Erosion measurements were performed at 1093C/2000F and at velocities of 800fps and 1600 fps using low incidence angle alumina particulate. YSZ powders from two sources were classified into two size ranges each and then plasma sprayed using five different torch designs. Torches included a Plasmadyne SG-100, a Metco 3MB, a Plasma Technic F-4, a Plasma Technic F-1-45 mini gun, and a Metco 7MB. A large range in erosion rates at both 800 fps and 1600 fps is reported for the fabrication variables considered in this paper. Additionally, a high velocity exponent is measured. (This work was supported by NCMS Project 140-0111-91061.)
10:50 AM		A2-8 Quantification of the Strength Modification of Thin Films at Elevated Temperatures K.-D. Bouzakis, N. Vidakis, K. David, A. Lontos (Laboratory for Machine Tools and Manufacturing Engineering, Mechanical Engineering Dept., Aristoteles University of Thessaloniki, 54006, Greece); T. Leyendecker, G. Erkens, H.-G. Fuss, R. Wenke (CemeCon, Germany) Thin hard coatings are usually hired to operate at elevated temperatures. Typical examples are coated tools used in high speed cutting, especially with continuous material removal, coatings in bearing applications and films used as thermal barriers to protect substrates from overheating. The operation of coatings at high temperature environments, modifies their bulk mechanical properties, such as elasticity modulus and hardness, as well as their fatigue and wear resistance. This paper presents a quantitative study of such phenomena, based on experimental data derived by the application of the impact test at elevated temperatures and cutting experiments. To carry out these tasks, special experimental test rigs have been designed and developed, being supported by SEM and EDX facilities. Additional FEM models were established to computationally sustain the experimental research action. By means of the aforementioned procedure a comprehensive study of the effect of coating technological specifications as well as of substrate, on the deterioration of their mechanical stress was incorporated. The remaining deposition stresses have been also examined for both mono and multilayer coatings.
11:10 AM		A2-9 Study of Micron Scale Thermal Properties of Layered Samples by Inversion of Photothermal Measurements: Application to Gun Tubes Inner Coatings C. Gervaise (ENSICA, France); C. Calderan (Université de Perpignan, France); C. Nouals (ENSICA, France); S. Benet (Université de perpignan, France); J.-J. Serra (CTA/LOT, France) Most of coated materials exhibit physical properties very different from that of bulk ones. Thermal ageing of such coatings modify their structure and consequently their properties. If the thermal ageing is due to a series of transient heat pulses, a physical properties gradient can be generated in the coating thickness. To investigate this phenomena, an experimental bench dedicated to the characterization of micron scale material thermal properties has been developped. Based on a modulated phoreflexion method, this bench was successfully used to NDC (non destructive control) and qualitative study of complex materials of with measurement maps are well correlated with material structure. Since the thermal waves penetration depth is function of the thermal excitation frequency, the capabilities of this methods to estimate the subsurface thermal properties distribution must be explored. In this article, we describe the application of an optimal estimation method to this problem. We will develop for that a global approach with: 1) a thermal transfer modelling, with 1D or 2D hypothesis, in multilayered samples ? a sensitivity coefficient study for main parameters 2) a study of the "ill posed" nature of these problems thanks to XX’ matrix 3) Monte Carlo simulations. This method will be applied to chromium coated steel samples, extracted from a gun tube after several shots, where the distribution of chromium diffusivity versus depth will be determined.Most of coated materials exhibit physical properties very different from that of bulk ones. Thermal ageing of such coatings modify their structure and consequently their properties. If the thermal ageing is due to a series of transient heat pulses, a physical properties gradient can be generated in the coating thickness. To investigate this phenomena, an experimental bench dedicated to the characterization of micron scale material thermal properties has been developped. Based on a modulated phoreflexion method, this bench was successfully used to NDC (non destructive control) and qualitative study of complex materials of with measurement maps are well correlated with material structure. Since the thermal waves penetration depth is function of the thermal excitation frequency, the capabilities of this methods to estimate the subsurface thermal properties distribution must be explored. In this article, we describe the application of an optimal estimation method to this problem. We will develop for that a global approach with: 1) a thermal transfer modelling, with 1D or 2D hypothesis, in multilayered samples, 2) a sensitivity coefficient study for main parameters, 3) a study of the "ill posed" nature of these problems thanks to XX’ matrix, and 4) Monte Carlo simulations. This method will be applied to chromium coated steel samples, extracted from a gun tube after several shots, where the distribution of chromium diffusivity versus depth will be determined.
11:30 AM		A2-10 X-ray Analysis of Magnetron Sputtered Tantalum Coatings Vs Electro-chemical Deposited Tantalum in Molten Salt S.L. Lee (US Army Armament Research Development and Engineering Center, Benét Laboratories); D. Windover (US Army Armament Research Development and Engineering Center); P. Cote (US Army Armament Research Development and Engineering Center, Benét Laboratories) Tantalum is an environmental-friendly, refractory metal with high melting point temperature. However, because of the differences in the properties of bcc ?- tantalum and tetragonal ?-tantalum, phase and structure optimization must be achieved for it to be useful as a good, protective coating for wear and erosion. Tantalum coated steel liners electrochemically-deposited in molten salt show superior behaviors compared to chromium coated steel liners. Tantalum coatings have also been successfully deposited onto the bore of medium and large diameter steel cylinders using cylindrical magnetron sputtering deposition technique. Sputtering deposition parameters control the ?- and ?- tantalum phase and structure in the nucleation and grain growth of the coatings. XRD, GIXRD and our high resolution pole figure techniques have been applied to study a number of triode, planar, and cylindrical magnetron sputtered specimens, as well as tantalum coated steel liners deposited in molten salt. A new technique using high resolution, high dynamic range, digital films in place of a conventional solid state X-ray detector, shows promising results for diffraction characterization of our tantalum coatings.