Encyclopedie de la recherche sur l'aluminium au Quebec - Edition 2014 | Page 74

72 TRANSFORMATION ET APPLICATIONS // TRANSFORMATION AND APPLICATIONS Tribology and HPT Deformation of Cold Sprayed Al- Al2O3 Composites as TRIBOLOGIE ET DÉFORMATION SOUS HPT DES COMPOSITES EN Al-Al2O3 DÉPOSÉS PAR Influenced by Al2O3 Particle Morphology PULVÉRISATION À FROID : INFLUENCE DE LA MORPHOLOGIE DES PARTICULES Al O 2 TRIBOLOGY AND HPT DEFORMATION OF COLD déformationO3 Tribologie et SPRAYED Al-Al2 sous HPT des par pulvérisation à froid: influence de la morphologie des particules Al2O3 3 composites MORPHOLOGY COMPOSITES AS INFLUENCED BY Al2O3 PARTICLEen Al-Al2O3 déposés J. Michael Shockley,1 S. Descartes,1,2 P. Vo,3 E. Irissou,3 R.R. Chromik1 2 1 1 Materials Engineering, McGill University, Montreal, QC Canada LaMCoS, UMR CNRS 5259 / INSA-Lyon, 69621 Villeurbanne, France 3 National Research Council, Boucherville, QC Canada INTRODUCTION TRIBOLOGY VS. SHEAR DEFORMATION Particle-reinforced aluminum matrix composites (Al-MMCs) generally exhibit lower wear rates and more stable friction than their un-reinforced matrix materials [1]. Cold spray is a popular consolidation route for Al-Al2O3, allowing for its application as a coating for corrosion and tribological protection. Previous work by the authors has found that 22 wt.% of angular Al2O3 particles leads to significantly lower wear rates and greater friction stability compared to unreinforced pure Al cold sprayed coatings (see figures below) [2,3] Pure Al (cold sprayed) Reciprocating Dry Sliding Wear High Pressure Torsion (HPT) Pure Al (cold sprayed) Contact Pressures: 0.5 GPa, 1.0 GPa Max. Hertzian Contact Pressure: 0.44 – 0.51 GPa ANG22 ANG22 Third bodies form through: • Plastic deformation constrained to a layer near the sliding interface • Tribochemical processes (oxidation in the case of Al-Al2O3) This study explores the influence of Al2O3 morphology (angular vs. spherical) on the dry sliding wear behavior of cold sprayed Al-Al2O3 at an intermediate range of Al2O3 content (~10 wt.%). To study the mechanisms of deformation-induced third body generation, high pressure torsion (HPT) was utilized to induce severe plastic deformation in shear on the same materials. HPT simulates certain aspects of tribological contact (compressive/hydrostatic stresses, shear strain) and can reveal details of third body mechanisms [4]. Al-Al2O3 MATERIALS STUDIED Al2O3 Recovery COLD SPRAY DEPOSITION OF Al-Al2O3 Coating Cross-Sections Deposition Efficiency “SPH11” 11 wt.% Al2O3 (Spherical) HPT testing provides: • Severe plastic deformation throughout the bulk of the material • Quantitative measures of stress and strain Process Schematic Plasma Giken PCS-800 “ANG10” 10 wt.% Al2O3 (Angular) Powder Feeder Feedstock Powders Al 6061 Substrate Angular Al2O3 (fused and crushed) d50 = 25.5 μm 50 µm 100 µm PRIX // AWARD Less spherical Al2O3 was recovered in the coatings compared to angular Al2O3, and spherical deposition efficiency was also lower. Dry Sliding Kinematics: 3 mm/s reciprocating motion 10 mm sliding amplitude ANG10 SPH11 James Michael Shockley Richard R. Chromik Département de génie mécanique, Université McGill Eric Irissou Phuong Vo Conseil national de recherches Canada (CNRC) To observe the influence of Al2O3 concentration on the dry sliding wear behavior, SPH11 and ANG10 were compared due to their similar Al2O3 concentrations and microhardness values. Spherical Al2O3 N2 N2 Preheat Temperature: 400 °C (fused and crushed, followed by plasma spheroidization) d50 = 24.26 μm Deposition Velocity: 582 m/s 50 µm HIGH PRESSURE TORSION EXPERIMENTS Dry Sliding Contact conditions: Spherical (6.35 mm diameter) sapphire counterface, 1.0 N normal load Estimated initial maximum Hertzian contact pressure: 0.44 – 0.51 GPa Friction vs. Cycle Number Converging-Diverging Nozzle 58.8 ± 4.7 HV200 DRY SLIDING WEAR EXPERIMENTS Chaire collégiale en transformation de l'aluminium Sylvie Descartes Département de génie mécanique, Université McGill, LaMCoS, INSA-Lyon, France 100 µm 58.2 ± 6.6 HV200 HPT Kinematics: 180° rotation 0.5 RPM Representative Stress-Strain Curves HPT Contact conditions: Cylindrical WC-Co anvils, 6 or 12 mm diameter Superficial contact pressure: 0.5 Gpa and 1 GPa SPH11 Wear Rates Friction Histogram Plots ANG10 SPH11 ANG10 SPH11 Assumption: Perfect adhesion between sample and anvils ANG10 Perspective of cross-sections ANG10: 500 Sliding Cycles SPH11: 500 Sliding Cycles Surface analysis of wear tracks reveals: • SPH11 wear tracks form smooth tribofilms • ANG10 shows evidence adhesion and smearing MML Al2O3 H = 0.9 25 µm Al 5 µm MML 0.2 GPa Microstructural analysis of wear tracks reveals: • Grain refinement in the mechanically mixed layer (MML) of both wear tracks • SPH11: Smooth, coherent MML 5-10 µm thick of elevated hardness (~3 GPa) • ANG10: Disordered, cracked MML 20-25 µm thick of lower hardness than SPH11 Microstructural analysis reveals: • Inhomogeneous Al microstructure near Al2O3 particles • Larger Al grains in pockets alongside particles • Effect is more pronounced for ANG10 than SPH11 Al2O3 100 µm 100 µm 10 µm MML H = 2.1 Al2O3 0.5 GPa MML H = 0.9 25 µm 5 µm ANG10: Post-HPT cross-section SPH11: Post-HPT cross-section 0.2 GPa 2 µm Upon looking closer: • “Tapering” effect interrupted by corners of ANG10 particles, leading to crack formation • Few if any cracks alongside SPH11 particles Al2O3 10 µm 2 µm Al2O3 Cold sprayed Al-Al Journée des étudiantsO–composites exhibit substantially improved wear resistance REGAL Les composites en Al-Al2O3 créés par pulvérisation à froid ont des propriétés tribologiques très élevées en terme d’usure et de friction, en comparaison à des revêtements en Al pur. Dans cette étude, le comportement pendant la déposition et des tests de frottement à sec ont été étudiés pour des revêtements en Al-Al2O3 présentant des concentrations de Al2O3 similaires mais avec des morphologies de Al2O3 variées. En comparaiso