LOGO Effect of nickel salts on the wear properties of electrodeposited nanocrystalline Ni-Co coating Chao Ma Supervised by : Dr. Shuncai Wang Prof. Frank Walsh

LOGO Outline 1. INTRODUCTION 1. INTRODUCTION 2. METHODOLOGIES 2. METHODOLOGIES 3. RESULTS AND DISCUSSIONS 3. RESULTS AND DISCUSSIONS 4. CONCLUSION 4. CONCLUSION 5. FUTURE WORK 5. FUTURE WORK

LOGO Cr(VI) Hard Cr Electrodeposition Introduction Nanocrystalline Wear and Corrosion Resistant Coatings as an alternative to hard Cr deposits Eletrodeposition is a low-cost and versatile technique to form the nano- crystalline coatings, which exhibit unique properties derived from their large number of grain boundaries compared to coarse-grained surface.

LOGO Good wear resistance Nanocrystalline Ni-Co coating Introduction High hardness Good corrosion resistance

LOGO Electrochemical Corrosion Behavior Crystal Morphology &Microstructure Hardness Process of Electroplating Introduction Tribology Properties

LOGO Microstructureanalysis 2 Electroplating 1 METHODOLOGIES SEM&EDS, TEM, XRD g/lSS1SS2SS3SS4 NiSO 4 6H 2 O NiCl 2 6H 2 O CoSO 4 H 2 O 100 Additives

LOGO Hardness test Tribology test 3 METHODOLOGIES 4 Wear volume was measured by an optical 3D surface profilometer Friction and wear behaviour were tested on a reciprocating pin-on-disc TE-77 tribometer

LOGO RESULTS AND DISCUSSIONS XRD Mixed structure of fcc and hcp Mixed structure of fcc and hcp with (111)α preferred orientation Independent of the nickel salts The finest grain size (5-10nm) is obtained from the coating prepared by NiSO 4 electrolyte. TEM NiCl 2 electrolyte NiSO 4 electrolyte

LOGO RESULTS AND DISCUSSIONS SEM Morphologies NiSO 4 electrolyte Adding NiCl 2 fine granular grains lens shape lens shape NiSO 4 -dominant electrolyte

LOGO RESULTS AND DISCUSSIONS The lens morphology significantly reduces the microhardness, which leads to the increasing coefficient of friction and wear rate. Tribology test NiSO 4 -dominant electrolyte Hardnesskg/mm Wear rate 10-4 mm3/Nm K= V/SF V is the wear volume (in mm 3 ) S the total sliding distance (in m) F is the normal load (in N) NiSO 4 electrolyte

LOGO RESULTS AND DISCUSSIONS SEM Morphologies NiCl 2 electrolyte Adding NiSO 4 pyramidal crystals NiCl 2 -dominant electrolyte

LOGO Tribology test Hardnesskg/mm Wear rate 10-4 mm3/Nm RESULTS AND DISCUSSIONS Decrease of internal stress Decrease of internal stress Variations of wear rate as a function of hardness Debris Traditional Archard’s Law Q=KLN/H NiCl 2 electrolyte NiCl 2 -dominant electrolyte

LOGO CONCLUSION Wear properties of electrodeposited nanocrystalline Ni-Co coatings are affected by different kind of nickel salts in electrolyte The corresponding changes of the morphology and the crystal may lead to different wear mechanisms The coating formed from NiSO 4 electrolyte performs better tribological behaviour, which can be attributed to the finest grain size and the fine granular grain morphology. NiCl 2 can increase the internal stress.

LOGO FUTURE WORK Electrodeposited Ni-Co coating Nucleation and growth of nanocrystalline Morphology Grain size Phase structure Hardness, Surface roughness, Adhesive interaction Internal stress Friction Wear Relationship of processing-microstructure and crystal morphology- tribological properties

LOGO UK-China Summer School on Tribology & Surface Engineering th August th August 2010 Chilworth Manor Hotel Chilworth Manor Hotel (2 mile away from the University of Southampton) (2 mile away from the University of Southampton) Sponsored by RCUK –Research Councils UK Sponsored by RCUK –Research Councils UK General Chair (UK and China): Prof. R.J.K. Wood, Vice President of the International Tribology Council Prof. Weimin Liu, Vice President of the Chinese Tribology Institute CONTACT DETAILS OF ORGANIZING COMMITTEE: Dr. S.C. Wang Tel. +44-(0)

LOGO Thank you for listening Questions?