Wear resistance of nanostructured Cr-based WC hardmetals sintered by spark plasma sintering

Erratum to 'Wear resistance of nanostructured Cr-based WC hardmetals sintered by spark plasma sintering' [International Journal of Refractory Metals and Hard Materials Volume 87, February 2020, 105121]. DOI: https://doi.org/10.1016/j.ijrmhm.2020.105206Nanostructured Cr-based WC hardmetals are successfully sintered by spark plasma sintering. The wear behaviour of these Cr-based WC hardmetals with different C contents ranging from 5.57 wt% to 6.91 wt%, is evaluated performing sliding wear tests under two different wear conditions. This work analyses the influence of the C content on the wear performance through the study of the phase formation and WC grain size. The Cr-based hardmetal with 5.57 wt% C content exhibits a lower wear rate than Co-based WC hardmetals tested under similar dry ball-on-plate wear conditions, even considering that these Co-based WC hardmetals have higher WC content (90 wt%) than Cr-based WC hardmetals (83.2 wt%). The combination of a nanosized WC grain and the avoidance of brittle (Cr,Fe)7C3 or soft graphite phases leads to a superior wear performance. Thus, the use of Cr-based binders in the hardmetal industry, alternatively to Co-based binders, is promising in applications in which high wear resistance is needed

Effect of mechanical alloying on the microstructural evolution of a ferritic ODS steel with (Y-Ti-Al-Zr) addition processed by Spark Plasma Sintering (SPS)

The high-energy milling is one of the most extended techniques to produce Oxide dispersion strengthened (ODS) powder steels for nuclear applications. The consequences of the high energy mill process on the final powders can be measured by means of deformation level, size, morphology and alloying degree. In this work, an ODS ferritic steel, Fe-14Cr-5Al-3W-0.4Ti-0.25Y2O3-0.6Zr, was fabricated using two different mechanical alloying (MA) conditions (Mstd and Mact) and subsequently consolidated by Spark Plasma Sintering (SPS). Milling conditions were set to evidence the effectivity of milling by changing the revolutions per minute (rpm) and dwell milling time. Differences on the particle size distribution as well as on the stored plastic deformation were observed, determining the consolidation ability of the material and the achieved microstructure. Since recrystallization depends on the plastic deformation degree, the composition of each particle and the promoted oxide dispersion, a dual grain size distribution was attained after SPS consolidation. Mact showed the highest areas of ultrafine regions when the material is consolidated at 1100 degrees C. Microhardness and small punch tests were used to evaluate the material under room temperature and up to 500 degrees C. The produced materials have attained remarkable mechanical properties under high temperature conditions.Authors want to acknowledge Ferro-Ness project and Ferro- Genesys project funded by MINECO under National I + D + I program MAT2016-80875-C3-3-R and MAT2013-47460-C5-5-P

Analysis of the interface and mechanical properties of field-assisted sintered duplex stainless steels

The development of duplex stainless steels produced by powder metallurgy represents an interesting alternative to conventional fabrication routes, since typical routes imply a strict control of composition and temperature during the processing path in order to avoid undesirable brittle phases. This work proposes a sintering route, designated as field-assisted hot pressing technique, in which an alternating current is applied to consolidate duplex stainless steels with different initial austenite percentages, always higher than ferrite. In all the cases, a thin and hard planar interface composed by two different microconstituents is generated between austenite and ferrite, growing inside the ferritic phase. The good mechanical properties achieved by these field-assisted sintered duplex stainless steels, in terms of nanohardness, elastic modulus, yield strength, ultimate tensile stress and ductility, establish these steels as promising candidates to be introduced in the market.This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The authors wish to express their gratitude to Dr. M.A. Monclús and Dr. M. Castillo-Rodríguez for their experimental and technical suppor

Effect of the heating rate on the microstructure of a ferritic ODS steel with four oxide formers (Y-Ti-Al-Zr) consolidated by spark plasma sintering (SPS)

The proposed ODS ferritic steel alloyed with (Y-Ti-Zr-Al) was produced by mechanical alloying (MA) and spark plasma sintering (SPS) to obtain a complex nanostructure. To densify the material, a sintering cycle by SPS was performed at 1100 degrees C using fast heating rates (from 100 to 600 degrees C/min). During the attrition of MA powders, the uneven distribution of deformation level and of alloying elements has produced an inhomogeneous recrystallization during the consolidation step. Influence of processing condition was studied by modifying the heating rate of SPS to promote a heterogeneous material with bimodal grain size distribution. The final microstructures were characterized by X-ray diffraction and electron microscopy (SEM and TEM). The mechanical behaviour at R.T. was characterized by means of the Vickers microhardness and micro tensile tests. The good balance obtained between ductility (similar to 22-26%) and yield stress (800-910 MPa) at room temperature is provided by the bimodal grain size distribution. To predict the experimental values depending on the processing conditions, a yield strength model is presented. This model covers the contribution of different strengthening mechanism from solid solution, grain size, dislocation density and oxides precipitation. The model indicates the dislocation density as the major strengthening contribution. In addition, small punch (SP) tests were performed to analyse the response of the material at high temperatures where remarkable properties have been achieved.Authors want to acknowledge Ferro-Ness project and Ferro-Genesys project funded by MINECO under National I+D+I program MAT2016-80875-C3-3-R and MAT2013-47460-C5-5-P.Publicad