Direct nano-crystalline Ni plating on titanium surfaces Dr Mohammad Sakhawat Hussain PhD (Aston) FIMF FIMMM CEng Department of Materials Engineering Faculty of Mechanical Engineering Universiti Teknologi Malaysia 2
OUTLINE PRESENTATION An innovative process for depositing Ni directly on Ti surfaces without the need to pre-treat the substrates with acid/s and preplate with an intermediate metallic layer As deposited Ni is nanocrystalline Nanomechanical test results to evaluate the mechanical properties of the as plated Ti/TiO 2 /Ni 3
Direct plating on Ti
High speed electroplating, which I have used for the first time to plate nickel on aluminium, titanium and stainless steel without any pretreatment process. 5
In order to plate nickel on titanium, oxide layers must be removed first by acid etching and plated with displacement reaction. The function of these immersion coatings is the replacement of the natural oxide always present on Ti irrespective of the cleaning process, with an oxide free metal on which adherent metallic coatings can be deposited. 6
Ni Anode + D.C Power Supply (Rectifier) Out In _ Control unit Temperature composition Cathode Flow Meter Filter Ni solution Magnetic Pump A Schematic diagram of the plating equipment designed for depositing Ni directly on titanium.
Low Speed solution Movement
High Speed solution Movement
Ni Deposit Oxide layer Ti base metal
Schematic Diagram: Aluminium has a porous and a fine compact oxide layer before pure Al can be exposed (the thickness of these oxide layers is less than 10 nanometer). 12
Aluminium has a porous and a fine compact oxide layer before pure Al can be exposed (TEM images showing oxide structures enlarged after anodizing ) 13
TEM images showing oxide structure
HIGH SPEED ELECTROPLATING SOLUTION PREPARATION PARAMETERS Research Methodology Type Constituents Typical Concentration Watt s Solution Nickel Sulphate Solution NiSO 4.7H 2 O NiCl 2.6H 2 O H 3 BO 3 NiCl 2.6H 2 O H 3 BO 3 g/l 300 45 38 ph 3.5 5.5 300 38 2.5 15
MORPHOLOGY ANALYSIS Specimen were cut by cross section Specimen were mounted using cold mounting Sample were grinding and polished with different abrasive paper. The thickness of nickel layer were measured using SEM to determined the effect of different solution, current density and temperature Research Methodology 16
Mechanism of electroplating and structure of electroplated coatings. 17
SEM image surface view of the Ni deposits showing the mechanism nucleation and growth of nano-crystalline Ni layer 18
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ADHESION TESTING Research Methodology Adhesion testing is required to quantify the strength of the bond between the nickel layer and aluminium substrate. Adhesion testing according to ASTM D6677 and ASTM D3359 ASTM D6677 - Adhesion testing by knife ASTM D3359 - Adhesion testing by tape test 22
ADHESION ANALYSIS Results & Discussion The sample of nickel layer which electroplated on high current density were easily to peeled off compared to sample which electroplated on low current density. I = 1 A at 55 o C I = 1 A at 65 o C Figure 4.: Nickel plating samples after adhesion testing. 23
Hardness resistance to penetration of a hard indenter Load is applied Plastic zone forms Hardness determined from optical measurements Background: hardness testing
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Micro- vs nanoindentation Hardness and micro-hardness testing Force is applied and optical inspection of hardness impression necessary No information on elastic modulus Results less useful for wear prediction Not suitable for thin films or coatings, or highly localised measurements Nanoindentation Force, displacement and time are recorded throughout the test Optical inspection of hardness impression is not required No other technique provides quantitative information on both elastic and plastic properties of thin films and small volumes Ideal for thin films, coatings, nanocomposites, biomaterials
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Ni Al Fig.5. Nanomechanical test results carried out on plated Al/(Al 2 O 3 )/Ni layers. The measured indentation modulus (Er) and hardness shows significant differences between the Ni plated layer and the aluminium base, however, the interface i.e. the oxide layer has very different measured values compared to Ni and Al. 28
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HRTEM Image showing 3 distinct layers i.e. Al, the oxide layer and the Ni coating. There is no sign of any porous Al layer.
Improved equipment for direct electroplating by using high speed electroplating process
Product of new equipment
CONCLUSIONS It has been possible to plate nickel directly on titanium without any pretreatment process, using a basic power supply and without any additives As plated the Ni is nanocrystalline Nanomechanical tests show Ni, aluminium oxide and Al all have different modulus and Hv, however, the oxide layer is much softer than expected and has shown inconsistent properties which indicates that the natural oxide was responsible for this inconsistencies. By increasing the temperature, the weight and thickness of the layer also increase. Nickel sulphate solution gives higher rate of deposition compare to the watt s solution. Adhesion between nickel and aluminium became low at current above 1 A. Nickel layer is easily to peel off. 33
Acknowledgement This work has been sponsored by Research Management Centre (RMC), Universiti Teknologi Malaysia. Industrial Partners: Hysitrion Inc. USA Micro Materials Ltd, UK MEng Research students (Nanomaterials Synthesis Group), Dept of Materials Engineering, UTM 34
THANK YOU 35