Deposition temperature influence on the wear behaviour of carbon-based coatings deposited on hardened steel

An evaluation regarding the influence of substrate material characteristics and deposition parameters on the tribological behaviour of carbon-based is presented. Chromium nitride interlayers and carbon-based thin films were deposited on hardened AISI 5115 case hardening steel, by magnetron sputtering. The physical vapour deposition (PVD) deposition was performed at three different temperatures: 180 °C, 200 °C and 250 °C. The chemical composition of the samples was assessed by Rutherford Backscattering Spectroscopy (RBS), the structure by X-ray Diffraction (XRD), and the surface morphology by Atomic Force Microscopy (AFM). The surface chemistry was analysed by X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy. The coatings are homogeneous, amorphous, with a smooth surface. The mechanical behaviour has been assessed on a pin-on disk rotational tribometer (wear characteristics), on a micro scratch tester (adhesion to the substrate), by ball-cratering (film thickness); by nanoindentation (hardness and the modulus of elasticity). A strong correlation between the substrate characteristics, but more importantly, of the deposition temperature, on one hand, and the mechanical characteristics, on the other hand, has been observed. The fracture toughness is positively influenced by the presence of the ceramic interlayer (chromium nitride). The modulus of elasticity and friction coefficient (both in dry conditions and lubricated) are decreased for higher deposition temperatures, however the higher deposition temperature negatively affects the hardness of the steel substrate.We hereby acknowledge the structural funds project PRO-DD (POSCCE, O.2.2.1., ID 123, SMIS 2637, ctr. no 11/2009) for providing some of the infrastructure used in this work

Assessing the Efficacy of Structural Merger Remedies: Choosing between Theories of Harm?

Collective dominance, Coordinated effects, Merger remedies, Single dominance, Tacit collusion, L13, L41,

The influence of powder particle and grain size on parts manufacturing by powder bed fusion

Nanostructured powder materials, or powders with increased amorphous ratio, can potentially lead to increased productivity during powder bed fusion, due to the hypothesis that nanostructured raw materials can be layer-sintered with lower specific energy, and consequently lower processing times when compared to commercial powders. Sintering of such materials can potentially be done faster, as compared to conventional powders. In addition, using nanostructured powders, or powders with high amorphous content, or even nanometric (nano-sized particles) powders, can result in higher density and hardness values of the sintered part, using the same process parameters. The main issue with nano-sized particles is their loss of flowability, which could be overcome by controlling the particle shape during manufacturing. This work presents our results concerning the manufacturing and characterization of titanium alloy powders, with potential use in additive manufacturing. The powders were manufactured using severe plastic deformation by mechanical milling from commercially available powders, with various rotation speeds, ball diameters, and milling periods, in order to obtain micrometric particles, but with nanometric or high amorphous content structures. The powders were further analyzed in terms of morphology, structure, and chemical composition

Assessing the Efficacy of Structural Merger Remedies: Choosing Between Theories of Harm?

Collective dominance, Coordinated effects, Merger remedies, Single dominance, Tacit collusion, L13, L41,

Metastable Al\u2013Si\u2013Ni alloys for additive manufacturing: Structural stability and energy release during heating

Rapid solidification with high cooling rates of metal alloys determines both the improvement of mechanical properties, due to the finishing of the structure, as well as obtaining metastable structures in the form of supersaturated or amorphous/nano solid solutions, which could potentially confer the material outstanding properties. It is of particular interest to use the energies released during the heating stage for these materials, due to the potentially lower input energy required to melt/fuse these materials. This phenomenon could add to the development and diversification of additive manufacturing technologies. The paper presents results concerning the structural development and phase transformation of metastable structures from Al\u2013Si\u2013Ni-based alloys, obtained by melt spinning and atomization techniques. It was observed that the structural transformations occurring during the heating process, starting from metastable structures, generate significant amounts of energy. This is of practical importance in the use of metallic powders in additive manufacturing technology, due to potentially reduced energy input