arXiv subjects

J. M. Alvarado-Orozco

Publications and source records attributed to J. M. Alvarado-Orozco.

7 recordsLinked to original sources

arXiv2020

Effect of Self-Lubricating Carbon Materials on the Tribological Performance of Ultra-High-Molecular-Weight Polyethylene

Ultra-high-molecular-weight polyethylene (UHMWPE) has been the gold standard for total knee replacements. Due to the knee's natural movements, UHMWPE wear debris production is inevitable. The debris, at the micron and submicron level, results in the joint's mechanical instability, reduced mobility, increased pain, and implant loosening. Wear debris production has been linked to UHMWPE mechanical properties; therefore, improvements to increase the UHMWPE mechanical properties will impact the component's longevity. Here, TiC coating and multiwalled carbon nanotubes (MWCNTs) were used to decrease the UHMWPE wear. After 400,000 cycles, the UHMWPE-MWCNT diminishes the mass loss compared to UHMWPE, and the combination with TiC decreased the material loss by ~ 43.7 % compared to the reference pair. Cold-flow and burnishing were the predominant wear modes.

cond-mat.mtrl-sci↗

arXiv2019

Effect of thermal treatments in high purity Ar on the oxidation behavior of arc-PVD c-Al0.66Ti0.33N coatings

The effect of temperature in high purity Ar (low oxygen partial pressure) on the oxidation and crystal phase evolution of c-Al0.66Ti0.33N arc-PVD coatings was investigated. High temperature tribology in Ar jet and adhesion behavior of the oxidized coating were addressed. The use of Ar protects the coating from the oxidation reactions and allowed to shed light into the details and paths of the nitride oxidation process. The c-Al0.66Ti0.33N nitrides were slightly oxidized in Ar even at high temperature. The surface chemistry evaluation shows very thin Al- and Ti-based oxide layers formation after 700C in Ar. However, the onset formation of the rutile TiO2 oxide was detected only after 900C and was clearly found by low-angle XRD diffraction after 1000C. XPS analysis of the oxidized samples at 800C indicated the formation of extremely thin layers mainly composed of mixed oxides a-Al2O3 g-Al2O3 and r-TiO2. Gradual changes in the chemical composition of the oxidized coatings observed at 900C clearly demonstrate the formation of gradient boundaries between Al-rich and Ti-rich oxy-nitride layers. After 1000C at least four oxides and oxi-nitrides layers and interlayers were found. Additionally, it is suspected that the transition oxide phases such as c-TiO, c-Al0.54Ti2.46O0.28N4.58, alpha-Al2TiO5 and TiOxNy might be precursors leading to the formation of thermodynamically stable rutile and alumina phases. Surface inspection after high temperature tribology in Ar jet showed formation of tensile cracks in the wear tracks and wear processes due to high size particle adhesion-abrasion and low size particle micro-ploughing of hard nitrides, oxi-nitrides and brittle oxide particles. Adhesion tests performed after high temperature tribology in Ar showed critical load decrease related to cohesive and adhesive damages at the contact point of the scratch track.

cond-mat.mtrl-sci↗

arXiv2018

Effect of pre-oxidation treatments on the structural, microstructural, and chemical properties of (Ni,Pt)Al systems

The effect of isothermal pre-oxidation treatments on the \b{eta}-(Ni,Pt)Al + René N5 system degradation is here reported. The oxidation treatments were carried out from 900 (mostly θ-Al2O3 growing conditions) to 1200°C (mainly α-Al2O3 growing conditions) for 5 h, under a purified Ar-stream with a fixed pO2= 1 x 10-5 atm. Results are discussed based on the correlation between the structural, microstructural and chemical properties of the \b{eta}-(Ni,Pt)Al BC showing that pre-oxidation parameters have an important effect on the multi-elemental counter diffusion phenomena along BC. For instance, a significant BC+IDZ thickness increase of 55% at 1200 °C was observed with respect to as-received sample just after 5 h of oxidation resulting in a severe BC degradation.

cond-mat.mtrl-sci↗

arXiv2018

Effect of Graded Bias Voltage on the Microstructure of arc-PVD CrN Films and its Response in Electrochemical & Mechanical Behavior

The effect of graded or constant bias voltages (-40 V, -80 V and -40/60/80 V) on size grain and surface defects of arc PVD deposited CrN films was investigated. Corrosion resistance evaluated using electrochemical impedance spectroscopy (EIS) and potentiodynamic curves (Tafel) and the mechanical behavior evaluated by means of instrumented nanoindentation and scratch testing was correlated with the microstructural changes. It was found that the bias voltage variation affects corrosion behavior due to the presence of defects (i.e. open voids, droplets) which also affects the failure mechanisms and increasing spallation. High bias voltage (-80 V) increases nano-hardness and the elastic modulus due to the dense microstructure of the CrN coating.

physics.app-ph↗

arXiv2018

Plasma-assisted nitriding of M2 tool steel: An experimental and theoretical approach

Present work was aimed to investigate the effect of nitriding time; 1, 1.5, 2.5 & 3.5 h, on surface characteristics & mechanical properties (surface nano-hardness, hardness Vickers, and adhesion) of AISI M2 tool steel. Mechanically effective compound (4 to 17.6 um) and diffusion layers (50.8 to 82.4 um) were obtained. Plasma nitriding considerably improved Surface engineering has been recognized as a family of technologies used to modify or improve the surface properties of a substrate. Nano-hardness, E-moduli and resistance to scratch of AISI M2 steel. Surface properties enhancement was associated to two harmonious effects at the nano-scale resulted by (a) stable nitride phases formation such as: gamma-Fe4N, epsilon-Fe2,3N, and (b) no brittle nitride networks and no critical decarburization of the steel upon nitriding. Thermodynamic calculations are in agreement with the experimental findings.

cond-mat.mtrl-sci↗

arXiv2018

Influence of HVOF parameters on HAp coating generation: An integrated approach using process maps

An experimental approach based on design of experiments, process maps and the analysis of deposition first stages to improve the biocompatibility of High-Velocity Oxygen Fuel (HVOF) hydroxyapatite (HAp) coatings is here presented. A two-level design of three factors (23) was performed using the stand-off distance (SOD), the fuel-oxygen ratio (F/O) and the powder feed rate (PFR). The effect of these experimental factors on the first stages of the coating formation was investigated to study the physical state of the particles before and after impacting the substrate. This study allowed the selection of the most suitable deposition parameter combinations to obtain HAp coatings with optimal crystallinity (> 45%), Ca/P ratio (approx. 1.67), phase content (> 95% of HAp), which guarantee the coatings mechanical stability and biocompatibility. The behavior of the coating within simulated body fluid (SBF) and cell culture (hFOB) was studied to analyze the apatite layer formation and the extracts cytotoxicity on human osteoblasts, respectively. The results show that the F/O ratio is the most influential factor on temperature and velocity on the in-flight particles and therefore on the coating properties. The SBF results confirmed the formation of an apatite layer after 14 days of immersion. Finally, the mitochondrial activity, measured by the MTS assay, and cell membrane integrity measures by LDH liberation assays, show that the coating released material does not induce toxicity on the exposed cells.

physics.app-ph↗

arXiv2018

Theoretical-Experimental failure analysis of the c-Al0.66Ti0.33N-M2 steel system using nanoindentation instrumented and finite element analysis

A theoretical-experimental methodology for failure analysis of the c-Al0.66Ti0.33N / Interface / M2 steel coating system is proposed here. This c-Al0.66Ti0.33N coating was deposited by the arc-PVD technique. For coating modeling the traction-separation law and the extended finite element method-XFEM were applied, the cohesive zones model was used for interface modeling and the Ramberg-Osgood law for substrate modeling. Experimental values using the instrumented nanoindentation technique, the scratch test and tensile stress test were obtained and introduced into the model. By means of nanoindentation the elastic modulus of coating, the fracture energy release rate and the nano-hardness. Normal and shear stress values of the interface were obtained with the scratch test, at the adhesive and cohesive critical loads. Vickers indentation was used to generate cracking patterns in the c-Al0.66Ti0.33N / Interface / M2 steel coating system. Radial and lateral cracks were generated and analyzed after transversal FIB cuts of the fracture zones. A finite element analysis was carried out to understand the relationship between the load-displacement curve and mechanical failure of in the system, associating the pop-in with nucleation, crack growth and cracking pattern. This works present a theoretical-experimental methodology for failure analysis of hard coatings (monolithic body) allowing to calculate fracture toughness of the coating material and model cracking patterns caused by contact mechanics.

cond-mat.mtrl-sci↗