LVIV POLYTECHNIC NATIONAL UNIVERSITY Modern Methods of Surface Engineering Institute of Engineering Mechanics and Transport Department of Applied Materials Science and Materials Engineering Asssistant professor, PhD. Tepla Tetiana
INTRODUCTION Surface engineering - is the sub-discipline of materials science which deals with the surface of solid matter. It has applications to chemistry, mechanical engineering, and electrical engineering. It is an enabling technology and can impact a wide range of industrial sectors.
INTRODUCTION Combining chemistry, physics, and mechanical engineering with metallurgy and materials science, it contributes to virtually all engineering disciplines. - It can be done on a given surface by metallurgical, mechanical, physical, and chemical means, or by producing a thick layer or a thin coating. - Both metallic and non-metallic surfaces can be engineered to provide improved property or performance. Texture d Multilayer Coatings
What are the benefits and there are they used? The surface engineering is to develop and implement procedures which a particular part or component the desired properties by controlling the characteristics of its surface. This type of treatment is used to: - Cutting - Forming - Decoration - Bio-medical - Automotive
What are the benefits and there are they used? Specific properties rely on surfaces - Wear, friction, corrosion, fatigue, reflectivity, emissivity, color, thermal/electrical conductivity, biocompatibility, etc. By improving durability, it reduces waste of natural resources and energy.
What are the benefits and there are they used? Benefits - Extend product life (durability) - Improve resistance to wear, oxidation and corrosion (performance) - Satisfy the consumer's need for better and lower cost components - Reduce maintenance (reliability and cost) - Reduce emissions and environmental waste - Improve the appearance; visually attractivity - Improve electrical conductivity - Improve solderability - Metallize plastic component surfaces - Provide shielding for electromagnetic and radio frequency radiation.
Scales of Surface Engineering Surface engineering technologies span: - Five orders of magnitude in thickness - It can vary from several mm for weld overlays to a few atomic layers or nanometers for physical vapor deposition (PVD) and chemical vapor deposition (CVD) coatings or ion implantation. Atomic-layer deposition is also possible. - Three orders of magnitude in hardness Superlattice Coatings Superhard CVD-Diamond Films Thermal Spray Coating
Scales of Surface Engineering Surface engineering technologies span: - Example of coating hardness range from 250-300 Hv for soft metal or spray coatings, 3500 Hv for Titanium Nitride PVD coatings and up to 10,000 Hv for diamond coatings - Almost infinite possibilities in the range of compositions and/or microstructure - Nano-composite, nano-layered, amorphous, crystalline, quasicrystalline, Etc Superlattice Coatings Superhard CVD-Diamond Films Thermal Spray Coating
Evolution and Significance of Surface Engineering Evolution of Coating Architectures Nanostructured, Superlattice, Gradient Single componen Multicomponent, Multilayer Adaptative (smart)
Evolution and Significance of Surface Engineering It is an enabling technology - It can combine various surface treatments with thin film and coating deposition. - It can improve wear and corrosion resistance of structural components. - It increases component lifetime and resistance to aggressive environments. - It can produce functional coatings that modify biocompatibility and optical and electrical properties of critical components
Classification of Surface Engineering Processes The traditional, well established processes: - Painting - Electroplating - Galvanizing - Thermal spraying - Plasma spraying - Nitriding - Carburizing - Boriding
Classification of Surface Engineering Processes The more technologically advanced coating technologies: -Physical vapor deposition (PVD) -Chemical vapor deposition (CVD) - Ion implantation - Ion-assisted deposition - Ion-beam mixing - Laser treatment - Femtosecond laser processing
Classification of Surface Engineering Processes Nowadays, a multitude of options are available to select and specify a treatment or a combination of treatments to engineer the surfaces of components or structures. Plasma Spray Plasma-source Ion Implantation Plasma Nitriding
Classification of Surface Engineering Processes
Classification of Surface Engineering Processes - Ion implantation - Laser treatment - Femtosecond laser treatment
Ion implantation
Ion implantation In ion implantation, ionized impurity atoms are accelerated through an electrostatic field and strike the surface of the target
Ion implantation
Ion implantation
Ion implantation
Ion implantation depth distribution of defects can be determined by Monte- Carlo-methods TRIM: Transport of Ions in Matter Stopping and Range of Ions in Matter does not take into account defect annealing, diffusion, dose rate effects and channeling defect concentration too large, but distribution can sufficiently be calculated maximum of defect density before maximum of implanted ions Depth distribution of atomic displacements
Ion implantation
Ion implantation Implantation-induced defect generation when transferred energy > displacement energy (10-40 ev): Frenkel pairs are generated as result of a displacement cascade vacancy only stable, when it is located outside of recombination volume of interstitial atom (size of this volume is temperature dependent) primary ion generates many vacancies, but only a few survive
Ion implantation Microstructure of V-alloy after ion implantation by Nitrogen
Ion implantation. Advantages - fast, homogenous on large wafers, reproducible result - exact control of implanted amount of dopant (measurement of current); especially important for small dopant levels - excellent cleaning of dopants during implantation by mass separation - simple mask techniques with thick oxide-, nitride- und photo lacquer layers - doping through thin passivation layers - doping profile easily adjustable by multiple implantation not possible by diffusion techniques) - very small device structures possible
Ion implantation. Disadvantages - irradiation damage up to amorphisation - additional annealing steps necessary (defect annealing) - doping atoms often not at regular lattice sites after implantation (interstitial position); electrical activation necessary by additional annealing (diffusion of dopants, danger of impurities) - implantation only possible for near-surface region - channeling leads to larger penetration depth of a fraction of dopant atoms
Ion implantation Change of material properties by ion implantation decrease of minority carrier lifetime: 1012 cm-2 B in Si t = 10-9 s free charge carriers are compensated; r = 106... 109 Wcm obtainable carrier mobility decreases too; may become smaller than 1 cm2 /Vs (normal >103 ) optical transmission becomes smaller by additional energy levels in the band gap refraction index changes (thus also reflection index): light propagates in an inner layer (integrated light pipe) SIMOX: hidden SiO2 isolation layer can be done by oxygen implantation and annealing for high doses: density- and volume change change of elastic and plastic properties (embrittlement of reaction pressure vessel steel in nuclear power plants)
Laser treatment Laser treatment
Laser treatment Basics of Implementation select a property improvement (i,e. wear, corrosion, erosion, lubricity, etc.) select a base alloy design an alloy surface that provides the improvement form a master alloy powder blend and apply it to the surface of the base alloy as a paint or thin film master alloy layer ~ 100-200 microns apply thermal energy via laser optics to melt the master alloy addition into the top layer of the base material -laser optics optimized to achieve uniform heating -laser optics dwell time very short, permitting rapid cooling and formation of refined grain, non-equilibrium structures -new alloy depth into base metal variable from 25-1000 microns -fiber-optic laser beam delivery permits precise control of location
Laser treatment Laser Induced Surface Improvement (LISI) Refined laser surface alloying Improved optics for flat beam profile Additive metallurgy process Uniform surface with low HAZ Full metallurgical bond with substrate
Laser treatment How does LISI compare to other processes? 1. Current limit due to laser spot size; anticipated change over next few year up to several hundred sq.ft./h. 2.Cost based on part complexity, quantity and current processing speed limitations.
Laser treatment
Laser treatment Technical Advances Permits precise selection of area to be modified Requires a very small amount of modifier alloy Results in extremely rapid heating and cooling of the surface Produces wide variety of chemical and microstructural states outside of typical phase diagrams Produces no distinct bondline; will not delaminate Requires little or no surface preparation for certain applications Produces minimal hazardous waste stream Performed remotely with robotics and fiber-optics Performed at rates between 20-50 sq.ft./h
Laser treatment LISI layer/base alloy transition In A356 Al
Laser treatment Steel Corrosion Protection Comparison of LISI Processed Plain Steel and 304 Stainless Under Accelerated Corrosion Conditions A - Carbon Steel 24 Hrs B - LISI Surface on Carbon Steel 232 Hrs C - 304 Stainless 232 Hrs
Laser treatment General Applications Corrosion Protection superior alloy, refined grain size current NAVAIR SBIR Cadmium replacement Environmental Substitution EPA funding as hard-chrome replacement process pumps, cylinders, rollers and die-casting dies Wear Resistance surface metal matrix composites using SiC, WC, TiC, TiB2, Al2O3, etc. Fracture Toughness Enhancement tough, softer layer on low toughness substrate
Laser treatment General Applications Surface Compatibility surface modification of dissimilar materials spark resistant surfaces for oxygen valves Durable Non-skid Surfaces Protection from hydrogen embrittlement current NASA program for SME Soft-Phase Surfaces current NASA program on cryogenic couplings
Femtosecond laser treatment Femtosecond laser treatment
Femtosecond laser treatment Femtosecond (FS) laser is an infrared laser with a wavelength of 1053nm. The first FS laser system was designed at the University of Michigan in the early 1990s
Femtosecond laser treatment A schematic of femtosecond laser system
Femtosecond laser treatment peak power laser pulse ~ 10 14 W pulse duration in the nanosecond range (10-9 second)
Femtosecond laser treatment
Femtosecond laser treatment In the materials under the influence of femtosecond pulses of moderate intensity phenomena: nonequilibrium heating and cooling relaxation of electrons and ions Conduction electrons during the absorption of laser irradiation are heated up to a temperature of 10000 K, while the crystalline lattice temperature remains below the melting point. The "hot" electrons emit light, i.e. there is a heat irradiation by "cold" metal. Generally, under the action of ultra-short pulses, formation of surface structures is accompanied by a set of non-stationary processes
Femtosecond laser treatment Schematic diagram of the laser beam profile focused on the entrance surface of a transparent dielectric material. The laser pulses are coming from the top of the diagram. The intensity distribution of each laser pulse is also indicated with reference to the surface damage threshold indicated by the dashed, horizontal line. a) high fluence used to produce high aspect ratio channels (b) intermediate fluence for pockets and surface patterning (c) low fluence, below surface damage threshold, for bulk modifications and exit surface structuring utilising nonlinear selffocusing (Kerr effect).
Femtosecond laser treatment Changing the scanning speed of the beam, we can change the width, structure, and morphology of the surface Microstructure of the surface layers of 04Х13AG20 steel after femtosecond laser treatment: a power 750 MW, Scanning speed of the laser beam 5 mm/s ; b power 750 MW, Scanning speed of the laser beam 10 mm/s
Femtosecond laser treatment Microtopography and the histogram of surface distribution of parameters of 04Х13AG20 steel structures after processing by the femtosecond laser
Femtosecond laser treatment Advantages Much less energy input is required to produce the same amount of material removal Thermal damage around the irradiated area is considerably reduced Multi-photon excitation can be exploited to achieve smaller structures There is no laser interaction with the ablated particles Non-linear optical processes in the dielectric material can be utilised to produce novel material processing possibilities
Femtosecond laser treatment Disadvantages Size restriction Not enough research data Expensive equipment
Conclusions Depending on your needs, we can choose the surface treatment methods.
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