Development of laser cladding MCrAlY coatings: high temperature friction and wear behaviour

Temperature can have a significant effect on the extent of wear damage of metallic components. Thermal barrier coatings with MCrAlY (where M=Ni, Co, Fe or combinations) alloys can improve the high temperature tribological and friction wear behaviour. In this work the dry friction and wear behaviour at room temperature and high temperature of new developed NiCoCrAlY and CoNiCrAlY laser cladding coatings were evaluated. Dense coatings, with good metallurgical bonding to the AISI 304 substrate was obtained by coaxial laser cladding tracks (40% overlapping), with previously optimized laser parameters. Tribological tests were performed by sliding wear at room temperature and 500 ºC, with an Al2O3 counterpart in ball on disk configuration tribometer. The wear scar surface was evaluated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) microanalysis. The 3D wear track topography was measured by inductive contact profilometer which enabled the wear rate calculation. The microstructure of the coatings consists of - Ni/-NiAl or -Co/-(Co,Ni)Al phases depending on the chemical composition of the alloy, as confirmed by X-ray diffraction (XRD) analysis. The wear test results show a reduction in wear rate at high temperature for all materials tested. For the NiCoCrAlY coating, the high temperature also reduces the friction coefficient, while it significantly increases the friction coefficient of CoNiCrAlY coating. The main damage mode is abrasion and adhesion, caused by oxides and partially-oxidized particles in the contact surface. The coatings and substrate results were compared, resulting in improved wear behaviour.The authors acknowledge the financial support of the Ministry of Science and Innovation of the Government of Spain through research project MAT2011-28492- C03 and the Generalitat Valenciana through ACOMP/2013/114 support. Professor Juan Carlos Pereira Falcón thanks the University of Carabobo for the financial support to pursue his doctoral studies at the UPV

Development of Ti–In alloys by powder metallurgy for application as dental biomaterial

Substantial progress has been made in Ti alloys’ properties and chemical composition. However, the effect of porosity and indium content on biocompatibility and corrosion behavior has not been sufficiently studied. Indium (In) is a promising nontoxic element that can replace other toxic elements, while porosity is associated with a good biological response. The purpose of this paper is to evaluate the achievability of three Ti–In alloys with 2.5, 5, and 10 wt.% Indium by powder metallurgy methods as dental prostheses. The findings of the present work showed that In acted as a grain refiner, and allowed us to obtain an 11.2-fold reduction for the Ti–10In sample than for the Ti–2.5In alloy. The total porosity of the Ti–In alloys decreased according to In content, however, grain size and In content showed a greater effect on the mechanical behavior in comparison with the effect of porosity, probably because of the low porosity percentage. All the mechanical values fell within the ranges accepted in the literature for dental implant applications. The Ti3+ and In3+ ion releases were below the toxic concentrations for the human body, with a maximum of 0.43 and 0.016 μg cm−2 h−1, respectively. Corrosion sensitivity decreased with In addition due to its surface protective effect on the Ti-matrix. These results proved that utilizing powder metallurgy methods, Ti–In alloys are feasible candidates for dental prosthesis. Of the three prepared Ti–In alloys, the Ti–10In alloy properties made it the most appropriate Ti–In alloy to be used as a dental implant

Development and characterization of a new predominantly β Ti–15Mo–5In alloy for biomedical applications

A new Ti–Mo–In alloy was designed for biomedical implant applications and produced by powder metallurgy. Mechanical properties, ion release, and electrochemical assessments were conducted to uncover its biomaterial feasibility. The Ti–15Mo–5In alloy consisted of a nearly equiaxed and micrometric β matrix with acicular α and fine dispersed α′′ phases. Mo and In chosen contents encouraged flexural strength (0.59 GPa) and hardness (3.9 GPa) beyond the values for human bone in the literature. As expected from the predominantly β microstructure, a medium value of elastic modulus (80 GPa) was obtained. The ion Ti (0.019 μgL−1 cm−2 h−1), Mo (0.622 μgL−1 cm−2 h−1), and In (0.001 μgL−1 cm−2 h−1) released concentrations were below harmful concentrations to human health. Corrosion rates during immersion and electrochemical tests (0.524 and 0.1 μm year−1, respectively) were lower than those reported for various implant materials. The Ti–15Mo–5In alloy is a feasible option for orthopedic and dental implants. Graphical Abstract: [Figure not available: see fulltext.]

Repetitive corrugation and straightening effect on the microstructure, crystallographic texture and electrochemical behavior for the Al-7075 alloy

Anti-corrosion susceptibility is one of the top criteria for selecting metallic materials for several industrial applications. This work studies the corrosion performance of an Al-7075 alloy obtained by repetitive corrugation and straightening (RCS). This processing method generated a microstructure formed by randomly distributed micro-, submicro-, and nano- metric grain sizes. The samples exhibited a drop in corrosion resistance for a longer duration in the electrolyte and higher deformation. However, the samples processed by RCS showed better electrochemical stability than the non-deformed condition. The improved electrochemical stability could be associated with the particular microstructure generated during the RCS process

Microstructural, mechanical, electrochemical, and biological studies of an electron beam melted Ti-6Al-4V alloy

This work studied the feasibility of an electron beam melting (EBM) Ti-6Al-4V alloy as a biomaterial for implants. Comparisons were made with a wrought forged Ti-6Al-4V alloy. The objective of this work was a detailed description of the microstructural and surface roughness effects on mechanical, electrochemical, and in-vivo biological performances. The EBMed condition showed higher mechanical properties, as well as higher electrochemical and ion release rates. These results were mainly influenced by the lamellar grain morphology and complex crystallographic texture of the EBMed alloy compared to the forged one. The higher area average roughness of the EBMed condition boosted the adhesion, proliferation, and biofilm formation of osteosarcoma (MG63), Staphylococcus epidermidis (S. epidermidis), and Staphylococcus aureus (S. aureus). The mechanical, ion release, corrosion, and in-vivo biological results in both studied conditions met the requirements for orthopedic and dental biomaterials. However, the forged condition is more recommended for patients with clinic stories related to S. epidermidis and S. aureus illnesses

Effect of the microstructure generated by Repetitive Corrugation and Straightening (RCS) process on the mechanical properties and stress corrosion cracking of Al-7075 alloy

This study discussed the effect of the heterogeneous microstructure generated through the Repetitive Corrugation and Straightening (RCS) process on the mechanical and stress corrosion cracking behavior of the AA7075. As a result of the RCS process, significant grain refinement was obtained. The average grain size ranged from 126 to 59 μm, for the initial condition and 4 RCS passes, respectively. The yield strength and hardness increased 170% and 15% from the initial pass, remaining almost constant afterward. The evaluation of stress corrosion cracking showed a decrement in the number of cracks of 21.6% and 23.5% between the initial condition and fourth RCS passes. The cracking and pitting corrosion were the dominant mechanisms in the tested samples. The mechanical and corrosion results were also discussed in terms of the microstructural features

Ion-exchanged geopolymer for photocatalytic degradation of a volatile organic compound

In thepresentworkitisshownhowgeopolymerscanbeusedtocontrolindoorandoutdoorair pollution byphotolysisof2-ButanoneasaVolatileOrganicCompound(VOC).Anionexchange procedurewasfollowedtoincorporateTiO2 into ageopolymer(IEG),anddifferent2-Butanone concentrations wereusedinabatchreactorunderdryandhumidconditions.Variationon 2-Butanone concentrationwasfollowedbygaschromatography.ALangmuir Hinshelwood modelwas used todeterminethedisappearancerateofreactantattheinitialstageofthereaction.Gasca-Tirado, J.; Manzano-Ramirez, A.; Vazquez-Landaverde, PA.; Herrera-Diaz, EI.; Rodriguez-Ugarte, ME.; Rubio-Avalos, JC.; Amigó Borrás, V.... (2014). Ion-exchanged geopolymer for photocatalytic degradation of a volatile organic compound. Materials Letters. 134:222-224. doi:10.1016/j.matlet.2014.07.090S22222413

Notes for genera: basal clades of Fungi (including Aphelidiomycota, Basidiobolomycota, Blastocladiomycota, Calcarisporiellomycota, Caulochytriomycota, Chytridiomycota, Entomophthoromycota, Glomeromycota, Kickxellomycota, Monoblepharomycota, Mortierellomycota, Mucoromycota, Neocallimastigomycota, Olpidiomycota, Rozellomycota and Zoopagomycota)

Compared to the higher fungi (Dikarya), taxonomic and evolutionary studies on the basal clades of fungi are fewer in number. Thus, the generic boundaries and higher ranks in the basal clades of fungi are poorly known. Recent DNA based taxonomic studies have provided reliable and accurate information. It is therefore necessary to compile all available information since basal clades genera lack updated checklists or outlines. Recently, Tedersoo et al. (MycoKeys 13:1--20, 2016) accepted Aphelidiomycota and Rozellomycota in Fungal clade. Thus, we regard both these phyla as members in Kingdom Fungi. We accept 16 phyla in basal clades viz. Aphelidiomycota, Basidiobolomycota, Blastocladiomycota, Calcarisporiellomycota, Caulochytriomycota, Chytridiomycota, Entomophthoromycota, Glomeromycota, Kickxellomycota, Monoblepharomycota, Mortierellomycota, Mucoromycota, Neocallimastigomycota, Olpidiomycota, Rozellomycota and Zoopagomycota. Thus, 611 genera in 153 families, 43 orders and 18 classes are provided with details of classification, synonyms, life modes, distribution, recent literature and genomic data. Moreover, Catenariaceae Couch is proposed to be conserved, Cladochytriales Mozl.-Standr. is emended and the family Nephridiophagaceae is introduced

Development of a porous Ti–35Nb–5In alloy with low elastic modulus for biomedical implants

A new porous Ti–35Nb–5In alloy was designed to join the advantages of low elastic modulus and non-toxicity, which are critical factors for biomedical implants. The Ti–35Nb–5In alloy was produced by powder metallurgy, and its feasibility as implant material was evaluated through mechanical properties, ion release, and electrochemical assessments. The microstructure of the Ti–35Nb–5In alloy consisted of acicular α-phase and fine α’’-phase within a micrometric β-phase matrix. A low elastic modulus of 63 GPa, as well as hardness and flexural strengths higher than the reported for the human bone, ensured the mechanical adequacy of the alloy. The Ti, Nb, and In releases were below toxic levels for the human body. The electrochemical performance showed the formation of a surface passive layer formation that encouraged a low corrosion rate. The corrosion performance was mainly influenced by chemical heterogeneities (preferred dissolution of Nb segregates) and porosity. Based on the above, the porous Ti–35Nb–5In alloy was demonstrated as a promising candidate for biomedical implant applications

A Novel Proposal to Manipulate the Properties of Titanium Parts by Laser Surface Alloying

A novel proposal is presented to increase the fatigue strength of titanium parts by applying a less rigid coating, which is expected to lower the tensile stresses at the surface and delay the onset of fatigue cracking. Niobium was introduced into the surface layer by laser surface alloying and, depending on the process parameters, beta and alpha" phases were obtained, resulting in a reduction of approximately 30% in Young's modulus and a more than 100% increase in hardness. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.The authors would like to thank the Sao Paulo State Research Foundation (FAPESP, Brazil) for financial support and Professor Conrado R.M. Afonso of the Structure Characterization Laboratory (LCE, Brazil).Fogagnolo, JB.; Rodrigues, AV.; Lima, MSFD.; Amigó Borrás, V.; Caram, R. (2013). A Novel Proposal to Manipulate the Properties of Titanium Parts by Laser Surface Alloying. Scripta Materialia. 68(7):471-474. doi:10.1016/j.scriptamat.2012.11.016S47147468