Corrosion and corrosion control

Adhesion and Adhesives Edited by Dr. R. Houwink and Dr. G. Salomon. Vol. 1: Adhesives. Second, completely revised edition. Pp. xvi + 548. (Amsterdam, London and New York: Elsevier Publishing Company, 1965.) 135s.

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Adhesion and Adhesives

Mechanical performance of additively manufactured meta-biomaterials.

Engineering failure analysis

Additively manufactured (AM, =3D printed) porous metallic biomaterials with topologically ordered unit cells have created a lot of excitement and are currently receiving a lot of attention given their great potential for improving bone tissue regeneration and preventing implant-associated infections. This paper presents an overview of the various aspects of design, manufacturing, and bio-functionalization of these materials from a "designer material" viewpoint and discusses how rational design principles could be used to topologically design the underlying lattice structures in such a way that the desired properties including mechanical properties, fatigue behavior, mass transport properties (e.g., permeability, diffusivity), surface area, and geometrical features affecting the rate of tissue regeneration (e.g., surface curvature) are simultaneously optimized. We discuss the different types of topological design including those based on beam-based unit cells, sheet-based unit cells (e.g., triply periodic minimal surfaces), and functional gradients. We also highlight the use of topology optimization algorithms for the rational design of AM porous biomaterials. The topology-property relationships for all of the above-mentioned types of properties are presented as well followed by a discussion of the applicable AM techniques and the pros and cons of different types of base materials (i.e., bioinert and biodegradable metals). Finally, we discuss how the huge (internal) surfaces of AM porous biomaterials and their pore space could be used respectively for surface bio-functionalization and accommodation of drug delivery vehicles so as to enhance their bone tissue regeneration performance and minimize the risk of implant-associated infections. We conclude with a general discussion and by suggesting some possible areas for future research.

/pdf/additively-manufactured-porous-metallic-biomaterials-470h2iyaoh.pdf

Additively manufactured porous metallic biomaterials

An automated method for detecting and classifying three classes of surface defects in rolled metal has been developed, which allows for conducting defectoscopy with specified parameters of efficiency and speed. The possibility of using the residual neural networks for classifying defects has been investigated. The classifier based on the ResNet50 neural network is accepted as a basis. The model allows classifying images of flat surfaces with damage of three classes with the general accuracy of 96.91% based on the test data. The use of ResNet50 is shown to provide excellent recognition, high speed, and accuracy, which makes it an effective tool for detecting defects on metal surfaces.

https://www.mdpi.com/2075-4701/10/6/846/pdf

Steel Surface Defect Classification Using Deep Residual Neural Network

This contribution is focused on the influence of build orientation on hardness of materials sintered using direct metal laser sintering (DMLS) technology. It builds on the current research works that has monitored the influence of build orientation on a fatigue life, mechanical properties, roughness after machining, etc. In the mentioned work, a slight influence of build orientation on the above properties was shown. The hardness was measured on a Ti6Al4V alloy which was made of powder by DMLS technology. The individual materials were sintered at different laser powers, then annealed to remove internal stresses. Part of the experiment examined the metallographic analysis of materials in the direction perpendicular to the sintered layers and parallel with the sintered layers. Microhardness was measured on metallographic cross-sections and the results were statistically processed. The influence of laser power on a respective material hardness was assessed by one-way analysis of variance (ANOVA), a comparison of the hardness between sintered and sintered-annealed samples, as well as the comparison of hardness in the two considered directions was performed by t-test and F-test. A statistically significant difference in the hardness of the materials prepared at different laser powers was found. The influence of heat treatment, as well as the direction of material building also showed a statistically significant difference.

https://www.mdpi.com/2075-4701/7/8/318/pdf

Influence of Build Orientation, Heat Treatment, and Laser Power on the Hardness of Ti6Al4V Manufactured Using the DMLS Process

This paper deals with the study of effects of mechanical surface preparation on the adhesion of coating with high content of zinc dust. Five kinds of mechanically blasted surfaces were studied. The following were used as abrasives: steel shot, steel grit, brown corundum oxide and zirblast. The last surface type was modified by MBX Blaster technology (mechanical bristle blasting). The surfaces topography was quantified by a roughness profilometer. The shape and size of the incurred inequalities on the modified surfaces were studied using 3D microscope images of the surface. The purity of the surfaces after pre-treatment was evaluated by impurity glued on the tape and measuring the reflection of light from the surface. Fractal analysis was used to evaluate the diversity of inequalities on the prepared surfaces. Cross-sections were also taken of the prepared surfaces. The prepared surfaces were coated with zinc-filled coating. The adhesion of the coating to the substrate was evaluated by a pull-off test afte...

A study of the effect of surface pre-treatment on the adhesion of coatings

Ti6Al4V samples have been prepared by Direct Metal Laser Sintering (DMLS) with varied laser power. Some of the samples were stress-relief annealed. The microstructure of materials was investigated using a light microscopy. Columnar grains of martensite dominate in as-made microstructure. Stress-relief annealing led to the white acicular phase growth in the structure with a fishbone arrangement on the boundary of some original martensitic needles. Mechanical properties of materials were characterized through hardness measurement in two directions relating to the sample building direction. It was found that the hardness of materials increased with a laser power and values varied from 370 to 415 HV 0.3/30. After stress-relief annealing, the structure of materials being homogenized, pattern spacing dissolved and the hardness in both directions became stabilized at values of 350–370 HV 0.3/30. The laser power affects the corrosion rate of the material. The lowest corrosion rate was recorded at the maximum laser power (190 W). Heat treatment does not affect the corrosion rate remarkably, however it leads to stabilization of corrosion potential of materials Ecorr. The surface of the samples was modified by an abrasive blasting using spherical (zirblast) and sharp-edged (white corundum) blasting abrasives and three levels of air pressure. The abrasive blasting of sintered materials led to a decrease of the surface roughness of materials with air pressure increasing. Blasting with zirblast led to a more significant decrease of roughness parameters compared with surfaces blasted with sharp-edged white aluminum. Different shapes of abrasives caused characteristic surface morphology.

Direct Metal Laser Sintering of Ti6Al4V for Biomedical Applications: Microstructure, Corrosion Properties, and Mechanical Treatment of Implants

This article deals with the evaluation of material wear of injection molds made of aluminium alloy Alumec 89 and copper alloy Moldmax HH in friction couples with polymer materials with various filler contents. The friction relations in injection molding were simulated in an adhesion dry wear test using an Amsler machine, with an area contact of the friction couple materials. The wear intensity was evaluated by determination of friction coefficient and relative wearing by the mass loss. Surface morphology changes of evaluated alloys after wear and the thermal conditions in particular friction couples were analyzed simultaneously.

Janette Brezinová

Papers

Steel Surface Defect Classification Using Deep Residual Neural Network

Influence of Build Orientation, Heat Treatment, and Laser Power on the Hardness of Ti6Al4V Manufactured Using the DMLS Process

A study of the effect of surface pre-treatment on the adhesion of coatings

Direct Metal Laser Sintering of Ti6Al4V for Biomedical Applications: Microstructure, Corrosion Properties, and Mechanical Treatment of Implants

Friction Conditions during the Wear of Injection Mold Functional Parts in Contact with Polymer Composites