International Journal of Microstructure and Materials Properties (12 papers in press)
The Influence of Laser Parameters on the Hardness Studies and Surface Analyses of Laser Alloyed Stellite-6 Coatings on AA 1200 Alloy: Response Surface Model Approach
by OLAWALE FATOBA, ABIMBOLA POPOOOLA, VICTOR AIGBODION, TSHIMANGADZO RAMBAU
Abstract: Improving the hardness values of AA1200 aluminium alloy using stellite-6 ceramic powder was investigated. A 4.4 kW Rofin Sinar Nd:YAG laser emitting 1.064
Keywords: Hardness; Microstructure; AA1200; Stellite-6; and Factorial design.
Special Issue on: Heat Treatment and Surface Engineering
EFFECTIVENESS OF DEEP CRYOGENIC TREATMENT IN IMPROVING MECHANICAL WEAR PROPERTIES OF COLD WORK TOOL STEELS
by Bojan Podgornik, Diego Ursic, Irena Paulin
Abstract: In recent years deep cryogenic treatment is getting increased attention in many tooling applications as a mean to improve tool performance. However, contradictory results are reported indicating improved as well as deteriorated wear resistance. The goal of this work was to investigate effect of deep cryogenic treatment on wear properties of tool steel and how they change depending on the tool steel type, and hardness and fracture toughness obtained. Results show that steel composition considerably affects the way how cryogenic treatment changes steel properties. For low carbon tool steel toughness properties can be improved for up to 70% at only minor hardness drop, but are quite limited in the case of high-speed steel, while at high carbon content both hardness and toughness are deteriorated. In general, deep cryogenic treatment was found to result in reduced abrasive wear resistance except for cases of combined hardness and fracture toughness improvement.
Keywords: deep cryogenic treatment; wear resistance; fracture toughness; hardness; tool steel.
Thermal characterization of cooling power of quenchants and its influence on microstructure evolution in EN19 steels using Jominy End Quench Test Setup
by Vivek Tiwary, Sharaschandra Kusugal, Rahul Zajari
Abstract: In this study, hardenability of EN19 alloy steel has been investigated for different quenchants using a Jominy test setup. During experimentation, the temperatures were recorded using a thermocouple inserted in the specimen. Hardenability curves, cooling curves, cooling rate curves and heat flux curves were determined and are presented graphically. Microstructures were developed at various sections of the quenched specimens to study the changes in the morphology of phases. Cooling power of the quenchants has been predicted based on the hardenability curves as well as thermal characterization. It is observed that brine solution results in more heat extraction from the steel specimens compared to other quenchants. The paper aims to establish that cooling rate curves and heat flux curves determination can be a suitable technique to characterize quenchants to assess its suitability for industrial applications.
Keywords: Jominy End Quench Test (JEQT); Hardenability; Heat Flux; Lumped Heat; EN19; Poly Alkaline Glycol (PAG).
Materials and Process Engineering Aspects of Warm Deep Rolling
by Torben Oevermann, Stephanie Saalfeld, Thomas Niendorf, Berthold Scholtes
Abstract: For industrial applications efficient and short processes are essential, justifying the increased complexity of deep rolling treatments at elevated temperature. For this purpose, the direct integration of deep rolling manufacturing steps in heat treatment processes is a promising strategy. Combining inductive heat treatment with deep rolling leads to encouraging results concerning near surface material states as well as resulting fatigue strengths. Different process concepts are introduced and discussed. Characteristic results of near surface microstructures and residual stress states produced in this way for steels SAE 1045 and SAE 4140 are presented. In addition, the consequences of the material states and the microstructures on cyclic deformation behavior and fatigue strength are outlined. The integrated system introduced allows the flexible application of appropriate process parameters, the analysis of their effects on the fatigue behavior and the determination of optimized process conditions.
Keywords: Deep rolling; fatigue; mechanical surface treatment; inductive heat treatment; deep rolling at elevated temperature; residual stress.
POWDER METALLURGY OPENS NEW WAYS FOR TOOL STEELS
by Massimo Pellizzari, Faraz Deirmina
Abstract: Powder metallurgy permits to produce tool steels with finer microstructure and improved mechanical properties compared to wrought ones. This major advantage was recently used by the author in designing new steel grades combining higher strength and toughness. Novel hybrid tool steels, by mixing hot work and high speed steel powders in different proportions, were developed looking at materials with properties tunable for a specific application. Near ultrafine grained materials could be obtained combining mechanical milling and spark plasma sintering, a fast consolidation technique assisted by pulsed current. Particle reinforced tool steel matrix composites have also been produced using the same approach. Finally, in order to look for steels combining high hardness and improved thermal conductivity hybrid tool steel-Cu grades were sintered. The aim of present paper is to give a general overview of the research activities and the opportunities opened by these new powder metallurgy products.
Keywords: tool steel; spark plasma sintering; ball milling; mechanical alloying.
Simulation of backup rolls quenching with experimental study of deep cryogenic treatment
by Pavel Krot, Sergey Bobyr, Maxim Dedik
Abstract: The research goals of this work are to simulate the phase transformations in heat treatment of large-scale rolls of special alloy steels including deep cryogenic treatment stage with experimental estimation of its influence on wear resistance of rolls. The adapted analytical models are introduced and applied for the calculation of phase transformations. Combination of finite-element models and experimental continuous cooling diagrams allowed determining the temperature and stress fields as well as each phase fraction in the special alloy steels 65Cr2Si3MoV, 50Cr5NiMoV and 70Cr3MnNiMoV at different stages of rolls manufacturing. Two short cycles of deep cryogenic treatment conducted on samples showed increased by 39% wear resistance of 65Cr2Si3MoV alloy steel compared to its standard heat treatment schedule.
Keywords: alloy steels; quenching; FEM models; rolls; cryogenic treatment.
ROBUST GENERATION OF BIO-INSPIRED ULTRAHYDROPHOBIC METALLIC SURFACES BY NANOSECOND PULSED LASERS
by Jose L. Ocaña
Abstract: The current availability of lasers with characteristic pulse lengths ranging from ns to fs and the development of the appropriate laser processing workstations granting the appropriate precision and repeatability have definitively consolidated laser surface microstructuring as a reference domain nowadays unavoidable for the design and manufacturing of microsystems: MEMSs, fluidic devices, advanced sensors, biomedical devices, etc., are all among the most well-know developments of laser micromanufacturing technology. In this line, the generation of surfaces with specific functional properties is becoming an important niche of applications. In this paper, the application of laser sources with emission in the UV and at ns time regime to the surface structuration of metal surfaces (specifically Al) for the modification of their wettability properties is envisaged, the generation of superhydrophobic self-cleaning extended functional surfaces being described.
Keywords: Laser Microstructuring; Short Pulse Lasers; Metallic Surfaces; Hydrophobicity; Self-cleaning.
The Application of Modern High-Energy Electron Beam Technologies
by Anja Buchwalder, Rolf Zenker
Abstract: High-energy electron beam (EB) is highly applicable for thermal processes like surface treatments, joining, ablating or for the additive manufacturing of metallic materials. Furthermore, many process-specific features may be regarded as beneficial characteristics, including the inherently high energy density and the various possibilities offered by high-speed beam deflection. The essentials of these different EB processes will be discussed and examples of applications demonstrated.
The main aim of EB surface treatments is the improvement of hardness, wear and/or corrosion resistance of local functional surfaces. The EB ablating is applied for producing inserts in cast components, for improving the adherence of spray coatings on substrates or for the generation of small lubrication dimples in bearings. EB welding, may be distinguished by narrow welds with extremely high depths and mostly without filler material. The EB additive manufacturing represent future-oriented technologies for the production of complex structures in modern industrial applications.
Keywords: electron beam; surface treatment; joining; ablating; additive manufacturing.
Special Issue on: News in Acoustic Emission Testing
Advanced Signal Analysis of Acoustic Emission Data to Discrimination of Different Corrosion Forms
by Luigi Calabrese, Massimiliano Galeano, Edoardo Proverbio, Domenico Di Pietro, Angelo Donato, Filippo Cappuccini
Abstract: The analysis of three corrosion phenomena (uniform corrosion, pitting corrosion and stress corrosion cracking) has been carried out through the use of acoustic emission technique. Corrosion attacks have been obtained on three different types of martensitic stainless steel in a FeCl3 solution, using conditions set by the ASTM G48 standard. These martensitic stainless steel used were characterized by different mechanical, microstructural and electrochemical properties, which lead to the development of specific corrosion forms, albeit the steels were tested in the same environmental conditions. A multivariate statistical analysis approach, based on PCA (Principal Component Analysis) and SOM (Self Organising Map), has been adopted to evaluate AE data and to obtain highlight damage-sensitive features. Specific clusters of variables related to specific corrosion phenomena have been identified, promoting this analysis approach as a potential procedure for discriminating onset of a specific corrosion mechanism.
Keywords: acoustic emission; principal component analysis; uniform corrosion; localized corrosion; stress corrosion cracking,.
The use of b-value and Ib-value of Acoustic Emission in monitoring Hydrogen Assisted Cracking of Martensitic Stainless Steel
by Luigi Calabrese, Massimiliano Galeano, Edoardo Proverbio, Domenico Di Pietro, Angelo Donato
Abstract: Hydrogen assisted cracking phenomena in tiosulphate solution of martensitic stainless steel was investigated by using acoustic emission technique. A time domain approach was adopted in order to analyse the corrosion phenomena by acoustic emission pattern time evolution. An appropriate set of variables was used, some of them directly related to the acoustic event waveform, while others have been derived from them, such as b-value and Ib-value, that are descriptors related to the time domain distribution of the acoustic event energies. Aim of this work is to show how these two descriptors allow to obtain an easy-to-use diagnostic system for damage progression, without a deep knowledge of the acting corrosion phenomena themselves.
Tests were carried out on a X12Cr13 martensitic stainless steel, according to NACE TM 0177 standard, using a modified sour simulated environment (5% NaCl, 2.5% Acetic Acid and 10-2M Na2S2O3).
Keywords: b-value; Ib-value; acoustic emission; stress corrosion cracking; time domain series.
Deformation and fracture analysis of nitrided steels by acoustic emission measurement
by Sergey Nikulin, Anatoliy Nikitin, Vladimir Khatkevich, Stanislav Rogachev
Abstract: The purpose of this work is to study the processes of static tension deformation and fracture of nitrided sheet samples of 08Kh17T (type AISI 439) and 15Kh25T (type AISI 446) steels using the acoustic emission method. The nitriding was performed with pure nitrogen, at T=1000-1100
Keywords: corrosion-resistant ferritic steel; high-temperature nitriding; tensile test; acoustic emission; deformation; fracture; strain hardening exponent.
Analysis of Fatigue Processes of SLM Materials by Acoustic Emission
by Vendula Kratochvilova, Frantisek Vlasic, Pavel Mazal, David Palousek, Libor Pantelejev
Abstract: The paper gives an overview of selective laser melting (SLM) materials properties focusing on fatigue processes and their acoustic emission. The selective laser melting technology belongs to rapid prototyping technologies and allows to quickly produce metal parts with complicated shapes. However the mechanical properties of these materials are currently worse than those of conventionally produced materials. Acoustic emission method was used to compare fatigue behaviour of SLM and conventionally produced materials. Tested materials were aluminium alloy AW-2618A (AlCu2Mg1,5Ni), copper alloy AMPCOLOY
Keywords: selective laser melting; acoustic emission method; fatigue; SLM; additive technology.