Łukasz Major

TEM Analysis of Wear of Ti/TiN Multi-Layer Coating in Ball-on-Disc Test

The wear mechanisms of Ti/TiN eight layered coatings ( =250nm) were investigated with ball-on-disc test. The coatings were obtained by hybrid pulsed laser deposition (PLD) technique. The wear test was done using Al2O3 ball-on-disc test at 1N/2000 cycles. Thin foils for TEM observations were cut from wear track using a Quanta 200 3D FIB (Focus Ion Beam) equipped with an Omniprobe lift-up system. The microstructure investigations were performed with the TECNAI G2 SuperTWIN FEG (200kV) transmission electron microscope. At the start of the wear the load applied to Al2O3 ball resulted in pushing-in of the coating into substrate causing its grooving of the shape corresponding to the ball diameter. The lining of the crater required strong coating deformation, which was plastic within Ti and mostly brittle in TiN layers. The vertical cracks in TiN were indeed stopped at the TiN/Ti interfaces, but reopen in lying below TiN layers. In applied wear conditions the continuity of Ti layers prevails over cracking of the TiN layers and resulted in layer-by-layer wear of investigated multilayer coating.

Mechanical and tribological properties of carbon-based graded coatings

The paper presents research on coatings with advanced architecture, composed of a Cr/Cr2N ceramic/metal multilayer and graded carbon layers with varying properties fromCr/a-C:H to a-C:N. The microstructure of the coatings was analysed using transmission electron microscopy and Energy Dispersive Spectroscopy, the mechanical properties were tested by nanoindentation, spherical indentation, and scratch testing, and tribological tests were also conducted. The proper selection of subsequent layers in graded coatings allowed high hardness and fracture resistance to be obtained as well as good adhesion to multilayers. Moreover, these coatings have higher wear resistance than single coatings and a friction coefficient equal to 0.25.

Effect of Interfaces on Mechanical Properties of Ceramic/Metal Multilayers

Multilayers of alternate Ti/TiN coatings deposited on X20Cr13 ferritic stainless steel by pulsed laser deposition (PLD) method have been tested using instrumented indentation. The effect of bilayer period and metal/ceramic thickness ratio were studied.

Adhesion of Cr/CrN Multilayers to Steel Substrates

Cr/CrN multilayers with a bilayer period λ = 62 ÷ 1000nm, were investigated. They were deposited by PLD technique on austenitic and ferritic stainless steel substrates. Coating hardness and adhesion to substrates were measured by nanoindentation and scratch testing. Multilayer properties were compared with single Cr and CrN coatings. The 2xCr/CrN and 4xCr/CrN multilayers exhibited hardness slightly lower than the hardness of a single CrN coating, while the critical load of the 4xCr/CrN multilayer, measured in the scratch test, was two times higher than for CrN. Furthermore, the character of coating failure also indicates the higher fracture toughness of multilayers than ceramic ones. The highest scratch resistance of the hardest multilayer with a bilayer period λ = 250nm is extremely interesting. The measured values of the critical loads LC1 and LC2 of all coatings were higher for harder ferritic than austenitic substrates. However, analysis of scratch track geometry indicated that coating failure occurred under the same deformation of the coating-substrate system, while the higher values of critical load for coatings on ferrite derived from the higher hardness of the substrate.

SEM and TEM Microstructure Characterization of a Commercial Purity Aluminum after Laser Treatment

The effect of the Laser Shock Processing (LSP) on the microstructure of the surface layer of a commercially pure alluminum was studied. LSP process was performed with a high-power Q-switched Nd:YAG ReNOVALaser, operating in a pulse mode (18 ns), with a power density of 0,43 GW/cm2. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and a Scanning Transmision Electron Microscopy (STEM) have been used to study the microstructure of the surface layer of the investigated material after laser treatment. SEM investigation showed that after LSP process surface melting occurs but is restricted to a thin layer. However, both TEM and STEM images indicate that under the thin melting layer a high density of dislocations were visible. It has been found that the laser beam with employing parameters caused plastic deformation of the surface layer of the investigated aluminum.

TEM Investigations of Damage Caused by Indentation of Multilayer TiN/Ti/a-C-H Coatings

The effect of damage on microstructure of multilayer coatings (TiN/Ti/a-C:H) have been analyzed. They were deposited through Pulsed Laser Deposition technique (PLD). The coatings microstructure was characterized using TECNAI F20 (200kV) FEG. The phase and chemical composition were described by EDS (Energy Dispersive X-Ray Spectroscopy) and electron diffraction patterns respectively. Coatings damage resistance was tested by pushing diamond ball with 1N of the applied load (static test). Thin foils were prepared directly from the wear track by focused ion beam method (FIB) using QUANTA 200 3D DualBeam. The multilayer coatings were characterized by strongly dislocated microstructure in TiN layers (like in single layered TiN), while a-C:H were amorphous. After mechanical test the multilayer TiN/Ti/a-C:H coating was strongly deformed. Ceramic TiN and a-C:H layers showed brittle cracking, while very thin metallic Ti layers (presented at each interface) deformed plastically. Deformation lines were propagating in 450 to crystalline growth direction. The wear of crystalline TiN layers caused cracks along {111} planes. The presence of metallic phase lead to the cracking resistance properties increase and the increase an energetic cost of propagating cracks.