Pub Date : 2022-09-06DOI: 10.17073/1997-308x-2022-3-37-44
V. A. Pesin, A. Osmakov, S. Boykov
Research into WC–Co submicron hardmetals involving measurement of hardness, coercivity and microstructural characterization, as well as analysis and comparison of results from recent literature led to the development of a unified constitutive expression for Vickers hardness in a form that separates the effects of the tungsten carbide grain size from those of the cobalt binder volume fraction. With the proposed expression for HV one may recalculate and compare hardness values for hardmetals featuring the same average grain size but differing in the binder matrix content. The paper shows that, in contrast to the Lee-Gurland model, the proposed constitutive expression framework treats the hardmetal hardness as a function of the carbide skeleton hardness (HWC) and contiguity (C) described as HV = CHWC. The carbide skeleton hardness depends on the WC grain size only, and it is described by the Hall-Petch equation. The results of parallel hardness and coercivity measurements led to an empirical equation relating Hc to the WC grain size and the Co volume fraction. Based on the complete experimental data, the relationship between the coercivity and Vickers hardness was explored, and a simplified relationship between these physical values was proposed to carry out the primary HV evaluation based on the measured coercivity values. As noted in the paper, the above equations are valid for relatively narrow WC grain size distributions with a maximum coefficient of variation of 0.5.
{"title":"Properties of WC–Co hardmetals as a function of their composition and microstructural parameters","authors":"V. A. Pesin, A. Osmakov, S. Boykov","doi":"10.17073/1997-308x-2022-3-37-44","DOIUrl":"https://doi.org/10.17073/1997-308x-2022-3-37-44","url":null,"abstract":"Research into WC–Co submicron hardmetals involving measurement of hardness, coercivity and microstructural characterization, as well as analysis and comparison of results from recent literature led to the development of a unified constitutive expression for Vickers hardness in a form that separates the effects of the tungsten carbide grain size from those of the cobalt binder volume fraction. With the proposed expression for HV one may recalculate and compare hardness values for hardmetals featuring the same average grain size but differing in the binder matrix content. The paper shows that, in contrast to the Lee-Gurland model, the proposed constitutive expression framework treats the hardmetal hardness as a function of the carbide skeleton hardness (HWC) and contiguity (C) described as HV = CHWC. The carbide skeleton hardness depends on the WC grain size only, and it is described by the Hall-Petch equation. The results of parallel hardness and coercivity measurements led to an empirical equation relating Hc to the WC grain size and the Co volume fraction. Based on the complete experimental data, the relationship between the coercivity and Vickers hardness was explored, and a simplified relationship between these physical values was proposed to carry out the primary HV evaluation based on the measured coercivity values. As noted in the paper, the above equations are valid for relatively narrow WC grain size distributions with a maximum coefficient of variation of 0.5.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73875227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-06DOI: 10.17073/1997-308x-2022-3-55-62
E. S. Novoselov, V. Almjashev, D. D. Nesmelov, D. Danilovich
The LaB6–VB2 alloy with the eutectic structure was obtained by cold crucible induction melting followed by crystallization. The mole ratio of components in the initial powder mixture was 35 : 65. The structure and composition of the LaB6–VB2 material were studied by X-ray diffraction, scanning electron microscopy, and X-ray microanalysis. The composition of the alloy is represented by two boride phases — cubic LaB6 and hexagonal VB2. Two-phase eutectic regions up to 500 μm in size represent a LaB6 matrix filled with 0.8–2.0 μm thick VB2 fibers (filamentary, rod crystals). VB2 fibers are predominantly oriented along the direction of the temperature gradient that appeared when cooling the melt, i.e. from the outer surface of the sample to its center. The integrated phase area analysis was used to determine the eutectic composition: 42 Ѓ} 1 mol% LaB6 and 58 Ѓ} 1 mol% VB2.
{"title":"Refinement of the eutectic composition in the LaB6–VB2 system","authors":"E. S. Novoselov, V. Almjashev, D. D. Nesmelov, D. Danilovich","doi":"10.17073/1997-308x-2022-3-55-62","DOIUrl":"https://doi.org/10.17073/1997-308x-2022-3-55-62","url":null,"abstract":"The LaB6–VB2 alloy with the eutectic structure was obtained by cold crucible induction melting followed by crystallization. The mole ratio of components in the initial powder mixture was 35 : 65. The structure and composition of the LaB6–VB2 material were studied by X-ray diffraction, scanning electron microscopy, and X-ray microanalysis. The composition of the alloy is represented by two boride phases — cubic LaB6 and hexagonal VB2. Two-phase eutectic regions up to 500 μm in size represent a LaB6 matrix filled with 0.8–2.0 μm thick VB2 fibers (filamentary, rod crystals). VB2 fibers are predominantly oriented along the direction of the temperature gradient that appeared when cooling the melt, i.e. from the outer surface of the sample to its center. The integrated phase area analysis was used to determine the eutectic composition: 42 Ѓ} 1 mol% LaB6 and 58 Ѓ} 1 mol% VB2.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75988799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-06DOI: 10.17073/1997-308x-2022-3-4-23
M. I. Aheiev, V. Sanin, N. Shvindina, Y. Kaplanskii, E. Levashov
The study covers the effect of alloying elements on the kinetics and mechanism of oxidation at 1150 °С for 30 hours of heat-resistant nickel alloys obtained using such technologies as centrifugal SHS metallurgy (SHS(M)), vacuum induction melting (VIM), elemental synthesis (ES), hot isostatic pressing (HIP). A comparative analysis was carried out for alloys based on nickel monoaluminide and standard AZhK and EP741NP alloys. It was found that kinetic dependences are described mainly by parabolic approximation. The logarithmic law of oxidation with the rapid (within 3–4 hours) formation of the primary protective layer is typical for alloys doped with molybdenum and hafnium. In the case of AZhK and EP741NP, oxidation proceeds according to a parabolic law at the initial stage (2–3 hours), and then according to a linear mechanism with the voloxidation and complete destruction of samples. Oxygen and nitrogen diffusion proceeds predominantly along the nickel aluminide grain boundaries and it is limited by the Al2O3 + Cr2O3 + XnOm protective film formation. SHS(M) alloys feature by a positive effect of zirconium and tantalum added as dopants on heat resistance. The Ta2O5 phase is formed in the intergranular space, which reduces the rate and depth of oxidation. The zirconium-containing top layer Al2O3 + Zr5Al3O0.5 blocks the external diffusion of oxygen and nitrogen, thereby improving heat resistance. Doping with hafnium also has a positive effect on oxidation resistance and leads to the formation of submicron and nanosized HfO2 inclusions that suppress the grain boundary diffusion of oxygen. MoO3, Mo3O4, CoMoO4 volatile oxides are formed in alloys with a high content of molybdenum and compromise the protective layer integrity. A comparative analysis of the oxidation kinetics and mechanism for samples consisting of the base β-alloy with Cr + Co + Hf additives showed a significant effect on the heat resistance of the sample preparation method. As the proportion of impurity nitrogen decreases and the Cr2O3 sublayer is formed, the oxidation mechanism also changes.
{"title":"Oxidation kinetics and mechanism of nickel alloys","authors":"M. I. Aheiev, V. Sanin, N. Shvindina, Y. Kaplanskii, E. Levashov","doi":"10.17073/1997-308x-2022-3-4-23","DOIUrl":"https://doi.org/10.17073/1997-308x-2022-3-4-23","url":null,"abstract":"The study covers the effect of alloying elements on the kinetics and mechanism of oxidation at 1150 °С for 30 hours of heat-resistant nickel alloys obtained using such technologies as centrifugal SHS metallurgy (SHS(M)), vacuum induction melting (VIM), elemental synthesis (ES), hot isostatic pressing (HIP). A comparative analysis was carried out for alloys based on nickel monoaluminide and standard AZhK and EP741NP alloys. It was found that kinetic dependences are described mainly by parabolic approximation. The logarithmic law of oxidation with the rapid (within 3–4 hours) formation of the primary protective layer is typical for alloys doped with molybdenum and hafnium. In the case of AZhK and EP741NP, oxidation proceeds according to a parabolic law at the initial stage (2–3 hours), and then according to a linear mechanism with the voloxidation and complete destruction of samples. Oxygen and nitrogen diffusion proceeds predominantly along the nickel aluminide grain boundaries and it is limited by the Al2O3 + Cr2O3 + XnOm protective film formation. SHS(M) alloys feature by a positive effect of zirconium and tantalum added as dopants on heat resistance. The Ta2O5 phase is formed in the intergranular space, which reduces the rate and depth of oxidation. The zirconium-containing top layer Al2O3 + Zr5Al3O0.5 blocks the external diffusion of oxygen and nitrogen, thereby improving heat resistance. Doping with hafnium also has a positive effect on oxidation resistance and leads to the formation of submicron and nanosized HfO2 inclusions that suppress the grain boundary diffusion of oxygen. MoO3, Mo3O4, CoMoO4 volatile oxides are formed in alloys with a high content of molybdenum and compromise the protective layer integrity. A comparative analysis of the oxidation kinetics and mechanism for samples consisting of the base β-alloy with Cr + Co + Hf additives showed a significant effect on the heat resistance of the sample preparation method. As the proportion of impurity nitrogen decreases and the Cr2O3 sublayer is formed, the oxidation mechanism also changes.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79493675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-06DOI: 10.17073/1997-308x-2022-3-45-54
V. S. Suvorova, A. Nepapushev, D. Moskovskikh, K. Kuskov
This research was conducted to obtain non-stoichiometric tantalum-hafnium carbonitride powder of the Fm3m (225) structural type using a combination of mechanical activation (MA) and self-propagating high-temperature synthesis (SHS) methods. Mechanical activation for 60 min in a low-energy mode (347 rpm) forms Ta/Hf/C composite particles 1 to 20 μm in size with a layered structure and contributes to a uniform distribution of elements. SHS of a mechanically activated Ta + Hf + C mixture in a nitrogen atmosphere (0.8 MPa) leads to the formation of a single-phase tantalum-hafnium carbonitride powder with the Ta0.25Hf0.75C0.5N0.3 composition where particles feature by a ≪spongy≫ morphology with pores and caverns and consist of submicron grains. Spark plasma sintering (SPS) was used to obtain a bulk sample of tantalum-hafnium carbonitride with a grain size of 3 to 5 μm, relative density of 98.2 Ѓ} 0.3 %, hardness of 19.8 Ѓ} 0.2 GPa, and crack resistance of 5.4 Ѓ} 0.4 MPa・m1/2. The kinetics of (Ta,Hf)CN oxidation at 1200 °C in air is described by a parabolic law suggesting the formation of an Hf6Ta2O17 + mHfO2 oxide layer with a low oxygen diffusion rate where the oxidation rate is 0.006 mg/(cm2・s). A (Ta,Hf)CN oxidation mechanism is proposed, which states that Ta2O5 and HfO2 are formed on the surface of grains at the first stage that react with each other at the second stage to form a Hf6Ta2O17 homologous superstructure and monoclinic HfO2. CO, CO2, NO and NO2 gaseous oxidation products are released with the formation of pores and cracks.
{"title":"Fabrication and oxidation resistance of the non-stoichiometric tantalum-hafnium carbonitride","authors":"V. S. Suvorova, A. Nepapushev, D. Moskovskikh, K. Kuskov","doi":"10.17073/1997-308x-2022-3-45-54","DOIUrl":"https://doi.org/10.17073/1997-308x-2022-3-45-54","url":null,"abstract":"This research was conducted to obtain non-stoichiometric tantalum-hafnium carbonitride powder of the Fm3m (225) structural type using a combination of mechanical activation (MA) and self-propagating high-temperature synthesis (SHS) methods. Mechanical activation for 60 min in a low-energy mode (347 rpm) forms Ta/Hf/C composite particles 1 to 20 μm in size with a layered structure and contributes to a uniform distribution of elements. SHS of a mechanically activated Ta + Hf + C mixture in a nitrogen atmosphere (0.8 MPa) leads to the formation of a single-phase tantalum-hafnium carbonitride powder with the Ta0.25Hf0.75C0.5N0.3 composition where particles feature by a ≪spongy≫ morphology with pores and caverns and consist of submicron grains. Spark plasma sintering (SPS) was used to obtain a bulk sample of tantalum-hafnium carbonitride with a grain size of 3 to 5 μm, relative density of 98.2 Ѓ} 0.3 %, hardness of 19.8 Ѓ} 0.2 GPa, and crack resistance of 5.4 Ѓ} 0.4 MPa・m1/2. The kinetics of (Ta,Hf)CN oxidation at 1200 °C in air is described by a parabolic law suggesting the formation of an Hf6Ta2O17 + mHfO2 oxide layer with a low oxygen diffusion rate where the oxidation rate is 0.006 mg/(cm2・s). A (Ta,Hf)CN oxidation mechanism is proposed, which states that Ta2O5 and HfO2 are formed on the surface of grains at the first stage that react with each other at the second stage to form a Hf6Ta2O17 homologous superstructure and monoclinic HfO2. CO, CO2, NO and NO2 gaseous oxidation products are released with the formation of pores and cracks.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73685746","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-06DOI: 10.17073/1997-308x-2022-3-63-77
A. Kudryashov, P. Kiryukhantsev-Korneev, S. Mukanov, M. Petrzhik, E. Levashov
Protective coatings were applied by electrospark deposition (ESD) using zirconium electrodes to improve the performance of the Ni-containing alloy obtained using the selective laser melting (SLM) technology. The kinetics of mass transfer was studied in 5 different frequency-energy processing modes. An analog-to-digital converter was used to determine the average number of pulse discharges, single-pulse energy, and the total energy of pulse discharges for 1 min of processing (ΣЕ) for all the modes used. In low-energy processing modes (ΣЕ = 1459÷2915 J), a weak mass transfer was observed, and the cathode weight gain was recorded only in the first minutes. As the processing time increased, a decrease in the substrate weight was observed. The roughness of coatings (Ra) varied in the range of 3.9–7.2 μm. In high-energy modes (ΣЕ = 5197÷17212 J), due to intense electrode heating, a steady cathode weight gain was observed, but the formed coatings featured by increased roughness: Ra = 7.4÷8.6 μm. The Ra parameter for the original SLM samples was 10.7 μm. The formed coatings featured by a thickness of 15–30 μm, high continuity (up to 100 %), hardness of 9.0–12.5 GPa, elastic modulus of 122–145 GPa, and friction coefficient of 0.36–0.49. The ESD processing promoted an increase in wear resistance of the SLM alloy by 7.5–20 times, and oxidation resistance by 10–20 % (t = 1150 °C, τ = 30 h). It was found that the coating obtained in the low-energy ESD mode with energy ΣЕ = 2915 J featured the best performance (hardness, modulus of elasticity, roughness, wear resistance and oxidation resistance).
{"title":"The effect of electrospark deposition using zirconium electrodes on structure and properties of nickel-containing alloy obtained selective laser melting","authors":"A. Kudryashov, P. Kiryukhantsev-Korneev, S. Mukanov, M. Petrzhik, E. Levashov","doi":"10.17073/1997-308x-2022-3-63-77","DOIUrl":"https://doi.org/10.17073/1997-308x-2022-3-63-77","url":null,"abstract":"Protective coatings were applied by electrospark deposition (ESD) using zirconium electrodes to improve the performance of the Ni-containing alloy obtained using the selective laser melting (SLM) technology. The kinetics of mass transfer was studied in 5 different frequency-energy processing modes. An analog-to-digital converter was used to determine the average number of pulse discharges, single-pulse energy, and the total energy of pulse discharges for 1 min of processing (ΣЕ) for all the modes used. In low-energy processing modes (ΣЕ = 1459÷2915 J), a weak mass transfer was observed, and the cathode weight gain was recorded only in the first minutes. As the processing time increased, a decrease in the substrate weight was observed. The roughness of coatings (Ra) varied in the range of 3.9–7.2 μm. In high-energy modes (ΣЕ = 5197÷17212 J), due to intense electrode heating, a steady cathode weight gain was observed, but the formed coatings featured by increased roughness: Ra = 7.4÷8.6 μm. The Ra parameter for the original SLM samples was 10.7 μm. The formed coatings featured by a thickness of 15–30 μm, high continuity (up to 100 %), hardness of 9.0–12.5 GPa, elastic modulus of 122–145 GPa, and friction coefficient of 0.36–0.49. The ESD processing promoted an increase in wear resistance of the SLM alloy by 7.5–20 times, and oxidation resistance by 10–20 % (t = 1150 °C, τ = 30 h). It was found that the coating obtained in the low-energy ESD mode with energy ΣЕ = 2915 J featured the best performance (hardness, modulus of elasticity, roughness, wear resistance and oxidation resistance).","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"26 1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89837130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-16DOI: 10.17073/1997-308x-2022-2-38-51
A. Potanin, E. Bashkirov, Y. Pogozhev, D. Kovalev, N. Kochetov, P. Loginov, E. Levashov
This study focuses on the combustion kinetics and mechanisms of reaction mixtures in the Mo–Al–B ternary system taken so that the MoAlB MAB phase was formed. The effect of the initial temperature on the key combustion parameters was demonstrated. Reaction mixture preheating was found to weakly affect the maximum combustion temperature. The effective activation energy of self-propagating high-temperature synthesis (SHS) was calculated. Phase diagrams in the Mo–Al–B system were built using the AFLOW and Materials Project databases. The phase composition and structure of the synthesized ceramics with MoAlB lamellar grains 0.4 μm thick and ~2–10 μm long as a main component were studied. The DXRD lines of MoB and Mo2B5 intermediate borides with their total content of ≤3 % were also identified. Scanning electron microscopy and energy dispersive spectroscopy studies revealed that the Al2O3 phase was present in the intergranular pores. A sequence of chemical transformations in the combustion wave was studied, and a hypothesis about the structure formation mechanism was put forward. MoO2 and Al2O3 can be the primary phases during SHS, and the MoAlB phase is formed from the boron-containing aluminum–molybdenum melt. Submicron-sized MoB precipitates are formed in the post-combustion zone due to the partial oxidation of aluminum by the dispersion strengthening mechanism.
{"title":"Self-propagating high-temperature synthesis of MoAlB boride ceramics based on MAB-phase","authors":"A. Potanin, E. Bashkirov, Y. Pogozhev, D. Kovalev, N. Kochetov, P. Loginov, E. Levashov","doi":"10.17073/1997-308x-2022-2-38-51","DOIUrl":"https://doi.org/10.17073/1997-308x-2022-2-38-51","url":null,"abstract":"This study focuses on the combustion kinetics and mechanisms of reaction mixtures in the Mo–Al–B ternary system taken so that the MoAlB MAB phase was formed. The effect of the initial temperature on the key combustion parameters was demonstrated. Reaction mixture preheating was found to weakly affect the maximum combustion temperature. The effective activation energy of self-propagating high-temperature synthesis (SHS) was calculated. Phase diagrams in the Mo–Al–B system were built using the AFLOW and Materials Project databases. The phase composition and structure of the synthesized ceramics with MoAlB lamellar grains 0.4 μm thick and ~2–10 μm long as a main component were studied. The DXRD lines of MoB and Mo2B5 intermediate borides with their total content of ≤3 % were also identified. Scanning electron microscopy and energy dispersive spectroscopy studies revealed that the Al2O3 phase was present in the intergranular pores. A sequence of chemical transformations in the combustion wave was studied, and a hypothesis about the structure formation mechanism was put forward. MoO2 and Al2O3 can be the primary phases during SHS, and the MoAlB phase is formed from the boron-containing aluminum–molybdenum melt. Submicron-sized MoB precipitates are formed in the post-combustion zone due to the partial oxidation of aluminum by the dispersion strengthening mechanism.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88016838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-16DOI: 10.17073/1997-308x-2022-2-61-69
A. Sytchenko, E. Levashov, P. Kiryukhantsev-Korneev
Mo–Si–B and Mo–Hf–Si–B coatings were produced by magnetron sputtering of a MoSiB ceramic target equipped with 2 or 4 Hf segments. Their structure and composition were studied by scanning electron microscopy, energy dispersive spectro scopy, X-ray diffraction analysis, and Raman spectroscopy. Mechanical properties were determined by nanoindentation at a load of 4 N. The crack resistance of coatings was studied on a microhardness tester at loads of 0.25–1.0 N. The oxidation kinetics was studied at 1000 °C in air with a total exposure of 300 min. The heat resistance of coatings was determined as a result of short-term annealing at 1500 °C. Electrochemical tests were carried out by voltammetry in the 1N H2SO4 solution. The results showed that the Mo–Si–B coating and Mo–Hf–Si–B coating obtained using 2 Hf segments feature by a columnar structure. The use of 4Hf segments in coating deposition led to an increase in density and suppression of the undesirable columnar structure formation. It was shown that hafnium introduction into the coating composition increases the growth rate by 20% and reduces the grain size of the main component of the h-MoSi2 phase by an order of magnitude, while simultaneously promoting HfB2 formation. Maximum hardness (27 GPa), Young’s modulus (370 GPa) and elastic recovery (62 %) were achieved for the Mo-Si-B coating. The hardness of coatings obtained using 2 and 4 Hf segments decreases by 1.9 and 1.6 times, respectively. During the Mo–Si–B and Mo–Hf–Si–B (2Hf) coating microindentation, radial cracking was observed. The sample obtained with the maximum concentration of hafnium featured by the best crack resistance. Electrochemical tests showed that the corrosion resistance of coatings increases in the Mo–Hf–Si–B (2Hf) → Mo–Si–B → Mo–Hf–Si–B (4Hf) series. All coatings showed good oxidation resistance at 1000 and 1500 °C. However, coating delamination areas were observed on the surface of Mo–Si–B and Mo–Hf–Si–B (2Hf) samples. The Mo–Hf–Si–B (4Hf) coating showed a lower oxide layer thickness and better oxidation resistance due to the dense SiO2 + HfOх protective layer formation.
{"title":"Structure and properties of Mo–Hf–Si–B coatings obtained by magnetron sputtering using MoSiB/Hf mosaic target","authors":"A. Sytchenko, E. Levashov, P. Kiryukhantsev-Korneev","doi":"10.17073/1997-308x-2022-2-61-69","DOIUrl":"https://doi.org/10.17073/1997-308x-2022-2-61-69","url":null,"abstract":"Mo–Si–B and Mo–Hf–Si–B coatings were produced by magnetron sputtering of a MoSiB ceramic target equipped with 2 or 4 Hf segments. Their structure and composition were studied by scanning electron microscopy, energy dispersive spectro scopy, X-ray diffraction analysis, and Raman spectroscopy. Mechanical properties were determined by nanoindentation at a load of 4 N. The crack resistance of coatings was studied on a microhardness tester at loads of 0.25–1.0 N. The oxidation kinetics was studied at 1000 °C in air with a total exposure of 300 min. The heat resistance of coatings was determined as a result of short-term annealing at 1500 °C. Electrochemical tests were carried out by voltammetry in the 1N H2SO4 solution. The results showed that the Mo–Si–B coating and Mo–Hf–Si–B coating obtained using 2 Hf segments feature by a columnar structure. The use of 4Hf segments in coating deposition led to an increase in density and suppression of the undesirable columnar structure formation. It was shown that hafnium introduction into the coating composition increases the growth rate by 20% and reduces the grain size of the main component of the h-MoSi2 phase by an order of magnitude, while simultaneously promoting HfB2 formation. Maximum hardness (27 GPa), Young’s modulus (370 GPa) and elastic recovery (62 %) were achieved for the Mo-Si-B coating. The hardness of coatings obtained using 2 and 4 Hf segments decreases by 1.9 and 1.6 times, respectively. During the Mo–Si–B and Mo–Hf–Si–B (2Hf) coating microindentation, radial cracking was observed. The sample obtained with the maximum concentration of hafnium featured by the best crack resistance. Electrochemical tests showed that the corrosion resistance of coatings increases in the Mo–Hf–Si–B (2Hf) → Mo–Si–B → Mo–Hf–Si–B (4Hf) series. All coatings showed good oxidation resistance at 1000 and 1500 °C. However, coating delamination areas were observed on the surface of Mo–Si–B and Mo–Hf–Si–B (2Hf) samples. The Mo–Hf–Si–B (4Hf) coating showed a lower oxide layer thickness and better oxidation resistance due to the dense SiO2 + HfOх protective layer formation.","PeriodicalId":14693,"journal":{"name":"Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional’nye pokrytiya","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82173146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-16DOI: 10.17073/1997-308x-2022-2-4-12
Yu. A. Avdeeva, I. Luzhkova, A. Ermakov
This paper provides the data on the composition and structure of nanocrystalline particles formed during the plasmachemical synthesis of mechanical mixtures containing TiC, Mo, and Co according to the plasma-induced Ostwald ripeningscheme. The paper was mainly intended to study the structural features and localizations of Mo0.42C0.58 carbide in TiC–Mo and TiC–Mo–Co nanocrystalline «core–shell» structures. As a result of X-ray diffraction and high resolution transmission electron microscopy (HRTEM) studies, it was found that the Mo0.42C0.58 carbide of orthorhombic modification is present in all fractions of TiC–Mo and TiC–Mo–Co mechanical mixtures after Ostwald ripening. Nanocrystalline TiC–Mo fractions and the TiC–Mo–Co mixture subjected to one-time Ostwald ripening from a baghouse filter were used in the electron microscopy study to illustrate the presence of «core–shell» structures where refractory cores are represented by Ti1–nMonCx titanium-molybdenum carbides, and high-contrast metal shells contain Mo, Mo0.42C0.58 and Co. Electron microscope images also showed the localization of orthorhombic Mo0.42C0.58. According to the results obtained, it can be concluded that «core–shell» structures are formed during the extreme exposure in the form of plasma-chemical synthesis of TiC–Mo and TiC–Mo–Co mechanical mixtures in a low-temperature nitrogen plasma. At the same time, it should be added that nanocrystalline compositions with the «core–shell» structure are crystallized in a tangential nitrogen flow at a cooling rate of 105 °C/s with the subsequent separation of products into ultra- and nanodispersed fractions in a vortex-type cyclone and a baghouse filter.
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Pub Date : 2022-06-16DOI: 10.17073/1997-308x-2022-2-79
A. Editorial
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