Oxidation kinetics of Cr-coated zirconium alloy: Effect of coating thickness and microstructure

Cr coatings with the thickness of 4.5–9.0 μm and dense/columnar microstructure were deposited onto Zr alloy by cooled or hot target magnetron sputtering. Steam oxidation tests were performed under temperature ramp from 500 to 1200 °C and isothermal treatment at 900−1200 °C for 10−30 min. The measurements of mass gain showed different oxidation kinetics depending on microstructure and thickness of the as-deposited Cr coatings. The dense microstructure is favorable to prevent alloy oxidation as long as the Cr layer is intact. The higher activation energy of 202 kJ/mol is observed for the dense 4.5 μm-thick Cr coating while thicker columnar coatings have 177−183 kJ/mol. The time of transition from protective to non-protective behavior increases with coating thickness. It was shown that the 9 μm-thick Cr coating with columnar microstructure better protects the zirconium alloy from oxidation at 1200 °C for 10 min in comparison with thinner coatings. The fast interdiffusion of Cr and Zr at coating/alloy interface significantly affects the oxidation kinetics of Cr-coated zirconium alloy at temperatures above 1100 °C and long oxidation time

Ultrasonic tomography of SiC-based materials synthesized by spark plasma sintering of preceramic paper

This paper is devoted to study a structure of SiC-based materials using ultrasonic tomography method. The SiC-based materials were fabricated from preceramic paper using spark plasma sintering (SPS) method. Also as part of the study the Young's modulus and density of sintered materials were determined and the effect of sintering pressure changing to this parameters value was investigated. The preceramic paper is a composite material including a matrix of organic cellulose fibers and inorganic powder filler (SiC). The sintering temperature and pressure were 2373 K and 20-40 MPa, respectively. The holding time for the sintering process was 10 min. The density of sintered materials was investigated by the hydrostatic weighing method. Ultrasonic tomography was implemented using of single-channel sensor at 10 MHz frequency. © Published under licence by IOP Publishing Ltd.Russian Science Foundation, RSF: 19-19-00192The research was supported by the Russian Science Foundation (grant No. 19-19-00192) as well as b

Ultrasonic tomography of SiC-based materials synthesized by spark plasma sintering of preceramic paper

This paper is devoted to study a structure of SiC-based materials using ultrasonic tomography method. The SiC-based materials were fabricated from preceramic paper using spark plasma sintering (SPS) method. Also as part of the study the Young`s modulus and density of sintered materials were determined and the effect of sintering pressure changing to this parameters value was investigated. The preceramic paper is a composite material including a matrix of organic cellulose fibers and inorganic powder filler (SiC). The sintering temperature and pressure were 2373 K and 20-40 MPa, respectively. The holding time for the sintering process was 10 min. The density of sintered materials was investigated by the hydrostatic weighing method. Ultrasonic tomography was implemented using of single-channel sensor at 10 MHz frequency

The influence of nickel layer thickness on microhardness and hydrogen sorption rate of commercially pure titanium alloy

The influence of nickel coating thickness on microhardness and hydrogen sorption rate by commercially pure titanium alloy was established in this work. Coating deposition was carried out by magnetron sputtering method with prior ion cleaning of surface. It was shown that increase of sputtering time from 10 to 50 minutes leads to increase coating thickness from 0.56 to 3.78 ?m. It was established that increase of nickel coating thickness leads to increase of microhardness at loads less than 0.5 kg. Microhardness values for all samples are not significantly different at loads 1 kg. Hydrogen content in titanium alloy with nickel layer deposited at 10 and 20 minutes exceeds concentration in initial samples on one order of magnitude. Further increasing of deposition time of nickel coating leads to decreasing of hydrogen concentration in samples due to coating delamination in process of hydrogenation

Comparative physical-tribological properties of anti-friction ion-plasma Ti-C-Mo-S coating on VT6 alloy or 20X13 and 40X steels

Results of comparative tests mechanical and tribological properties of solid antifriction Ti-C-Mo-S coating, deposited by magnetron-plasma combined sputtering method on substrates of VT6 titanium alloy, 40X and 20X13 hardened steels are provided. Coating is sputtered using the same conditions and technological regimes on substrates of different materials. However, the friction tests results showed significant difference in tribological characteristics of coating depending on type of material used for substrate, first of all by wear-resistance ability. Authors suppose that this is due to difference between physical properties such as composition and structure of substrate materials that determines hardness and coating adhesion to surface

The influence of nickel layer thickness on microhardness and hydrogen sorption rate of commercially pure titanium alloy

The influence of nickel coating thickness on microhardness and hydrogen sorption rate by commercially pure titanium alloy was established in this work. Coating deposition was carried out by magnetron sputtering method with prior ion cleaning of surface. It was shown that increase of sputtering time from 10 to 50 minutes leads to increase coating thickness from 0.56 to 3.78 ?m. It was established that increase of nickel coating thickness leads to increase of microhardness at loads less than 0.5 kg. Microhardness values for all samples are not significantly different at loads 1 kg. Hydrogen content in titanium alloy with nickel layer deposited at 10 and 20 minutes exceeds concentration in initial samples on one order of magnitude. Further increasing of deposition time of nickel coating leads to decreasing of hydrogen concentration in samples due to coating delamination in process of hydrogenation

SiC- and Ti3SiC2-Based Ceramics Synthesis by Spark Plasma Sintering of Preceramic Paper

This paper is devoted to proposing a new approach to the synthesis of SiC- and Ti3SiC2-based ceramics by using of preceramic paper as a feedstock. A preceramic paper with SiC and Ti3SiC2 powder fillers were sintered by spark plasma sintering (SPS) method for holding time 10 minutes under pressure 20-100 MPa. The temperature for the sintering of SiC- and Ti3SiC2-filled paper was 2073-2373 K and 1373-1473 K respectively. The influence of sintering parameters on the materials microstructure was analyzed by scanning electron microscopy. It was revealed that with an increase in pressure from 20 to 100 MPa, the microstructure of the materials becomes denser. It agrees with the results of measuring the density of the sintering materials by the hydrostatic weighting. The determination of Young`s modulus by the acoustic method demonstrates that with the increase of the applied pressure during SPS, Young’s modulus of the synthesized SiC- and Ti3SiC2-ceramics increase

Influence of preceramic paper composition on microstructure and mechanical properties of spark plasma sintered Ti3SiC2-based composites

AbstractThis paper describes the effect of preceramic paper composition on microstructure and mechanical properties of Ti3SiC2-based composites. The preceramic paper with Ti3SiC2-powder filler and different content (from 10 to 40 wt.%) of organic component (cellulose) was prepared. The composites were obtained by spark plasma sintering (SPS) at 50 MPa pressure for 10 min holding time. The sintering temperature was 1473 K. The influence of organic content on microstructure, phase composition, and flexural strength of the sintered materials was analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and mechanical testing, respectively. It was revealed that the microstructure of the sintered materials became more porous with increasing of cellulose content in the paper. XRD analysis showed the presence of Ti3SiC2, TiC and TiSi2 phases in the sintered samples while the content of the Ti3SiC2 phase increase with decreasing of the organic content. The flexural strength changes from 100 (40 wt.%) to 300 MPa (10 wt.% organic binder) that is caused by porosity of the composites