水热碳对粉末冶金生产的铁基复合材料的影响外文文献

Materials Chemistry and Physics 242 2020 122557 Available online 13 December 2019 0254 0584 2019 Published by Elsevier B V Hydrothermal carbon effect on iron matrix composites produced by powder metallurgy Hamza Simsir a Yasin Akgulb Mehmet Akif Erdenc aTurkish Chambers and Stock Exchange Technical Science Vocational School Karabuk University 78050 Karabuk Turkey bDepartment of Metallurgical and Materials Engineering Karabuk University 78050 Karabuk Turkey cDepartment of Biomedical Engineering Karabuk University 78050 Karabuk Turkey H I G H L I G H T S G R A P H I C A L A B S T R A C T HTC iron composites were produced by powder metallurgy Mechanical properties of composites were improved with the increasing of HTC HTC amount Low amount of HTC HTC in iron ma trix was positively effective on corrosion rate A R T I C L E I N F O Keywords Hydrothermal carbon Iron Composite Powder metallurgy A B S T R A C T In this work hydrothermal carbons HTC were obtained from glucose at 200 C for 30 h HTC and its calcinated product HTC were added to pure iron powder with different ratios 0 25 0 50 and 0 75 wt to obtained HTC reinforced iron composites by powder metallurgy To our knowledge this is the first study that investigates the effect of HTC on iron matrix composites Microstructure hardness compression and corrosion behaviors of composites were investigated According to the results mechanical properties of composites were enhanced with the increasing of HTC HTC amount However high corrosion resistances were gained with the using of the low amount of HTC 0 25 and 0 50 wt and HTC 0 25 wt 1 Introduction To date powder metallurgy conventional casting in situ reaction technique machining and self propagating high temperature synthesis have been used for producing metal based composites 1 Among these processes powder metallurgy P M consists of compression of powders and sintering 2 versatile and efficient route for producing metal ma trix composites with combining various materials 3 Mostly metal matrix composites produced by P M has possessed better mechanical properties than casting process products as more homogeneous struc ture has been occurred 4 As well as with the using of casting process segregation contamination of metal matrix and inclusion could be happened too But P M has enabled to produce metal matrix composites not only without these disadvantages of casting but also with low pro duction cost 5 6 Although conventional production methods of iron steel components have required high melting temperatures these components could be produced via P M at lower temperatures 7 Many studies have been conducted to increase performance of iron Corresponding author E mail address hamzasimsir karabuk edu tr H Simsir Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage https doi org 10 1016 j matchemphys 2019 122557 Received 6 May 2019 Received in revised form 24 October 2019 Accepted 13 December 2019 Materials Chemistry and Physics 242 2020 122557 2 matrix composites via P M 8 12 Pagounis et al investigated wear properties of TiC 5 30 vol white cast iron composites Results show that higher wear resistance and hardness of composite were gained with an increment of TiC amount 10 11 Srinivasa et al 9 studied the effect of SiC content on the feasibility of SiC iron composites via laser sintering It was found that hardness of composites was improved with the increasing of SiC content Gupta et al 13 compared to the corro sion behavior of pure iron Fe and Fe Al2O3 composites It was observed that addition of Al2O3 to iron matrix led to enhancement of corrosion resistance of iron In another study Turkmen was investigated different amount of graphite 0 15 0 65 wt effect on iron matrix via P M 14 According to this study increasing of graphite amount resulted in higher strength rate but lower ductility In recent years carbonaceous additives such as carbon nanotubes graphene and fullerene have become popular for metal matrix com posites due to their unique mechanical properties Studies show that these reinforcements lead to enhancement of mechanical properties of metals even at very low amounts 2 15 16 But these nanosized carbons have been produced with high production costs 17 But hydrothermal carbons HTCs present not only the low production costs but also some other advantages i HTCs can be obtained from almost any type of biomass such as carbohydrates cellulose sea plant derivates food wastes etc ii HTCs have been synthesized at mild reaction conditions 180 350 C in water iii Since the carbonization has carried out in water any pre drying process for wet biomass does not need In addition to this advantages HTCs has been used in many different areas such as lithium or sodium ion batteries 18 19 supercapacitors 20 catalytic reactions 21 adsorbent materials 22 nanocomposites 23 mag netic materials 24 etc Although HTCs have been used many applica tion areas as mentioned above to the best of our knowledge there is no study on HTC reinforced iron matrix composites via P M In this study effect of different amounts HTC and calcinated HTC HTC on the mechanical and corrosion properties of composites was investigated 2 Experimental section 2 1 Production of materials In order to produce HTC 1 5 gr glucose and 20 ml deionized water were placed stainless steel autoclave Teflon lined The autoclave was put into pre heated furnace at 200 C for 30 h Obtained HTCs were washed with distilled water few times then filtered and dried at 105 C for 2 h These carbons were labeled as HTC Then HTCs were calcinated at 600 C temperature for 6 h in a tube furnace under argon gas During the calcination process HTCs were deoxygenated and they were labeled as HTC The iron powders were mixed with different amounts of HTC or HTC 0 25 0 50 and 0 75 wt in a Turbula mixer for 1 h Mixed powders were compacted at 750 MPa pressure by using a hydraulic press with 96 tons capacity Hidroliksan HD100 2017 The mold was pre pared according to ASTM E8 E8M 11 powder metal mold standard Obtained 32 mm billet products were sintered under argon gas atmo sphere in a tube furnace at 1200 C for 1 h Heating and cooling rates of the furnace were carried out at 5 C min 2 2 Characterization Metallographic process of samples was carried out grinding polish ing and etching with the using of 2 00 vol nital solution Microstruc ture analysis of samples was characterized by Nikon MA200 Optical Microscope and Zeiss Ultra Plus Scanning Electron Microscope SEM Functional chemical groups of HTCs were detected by Bruker ALPHA Platinum FTIR ATR spectrometer equipped with a single reflection diamond ATR accessory HTCs were analyzed from 4000 to 600 cm 1 wavenumbers 6 scans at 1 cm 1 spectral resolution Densities of sam ples were measured according to the Archimedes method by Radwag precision scales Vickers microhardness tests were performed for each sample for 5 times with using QNESS Q10A machine under a load of 1 kg for 15 s dwelling time Compression test was conducted for 10 10 10 mm cubic samples by using Zwick Roell 600 kN Test Device with 0 02 mm min compression rate at room temperature Ultimate compression strength UCS value was calculated at 0 5 strain value for all samples Potentiodynamic corrosion tests were conducted by Parstat 400 Potentiostat 1 mV s scan rate and from 0 5 V vs open circuit potential to 0 5 V to open circuit potential in 3 5 wt NaCl Merck solution at room temperature for 30 min Three electrode cells consist of a graphite counter electrode a reference electrode Ag AgCl 3 5 mol KCl and working electrode prepared samples were used Surface area density and equivalent weight of working electrodes were determined as 0 27 cm2 7 8 g cm3 and 18 61 respectively Corrosion rate is calculated as Corrosion Rate K icorr EW Density 1 Where K is a metric conversion factor 3 27 x 10 3 mm g A cm year Icorr is the corrosion current density EW is equivalent weight which is calculated as Equivalent weight X fi ni wi 1 2 Where fi is the mass fraction ni is the valance of element in the com posite and wi is the atomic weight 25 Fig 1 SEM images of a HTC and b HTC Fig 2 FTIR spectra of a glucose b HTC and c HTC H Simsir et al Materials Chemistry and Physics 242 2020 122557 3 3 Results and discussion 3 1 Characterization of hydrothermal carbon The morphology of HTCs and HTC were characterized by SEM As can be seen from Fig 1a formation of hard spheres took place and they were approximately 1 4 m radius size with homogenous distribution Although after the calcination process the sizes of spheres were around 1 0 m no change of spherical morphology were observed Fig 1b Similar results have been reported in a previous study 19 The functional chemical structure of carbon materials was deter mined by FTIR analysis It is well known that after the HTC process of glucose precursor at similar reaction conditions the intensity of C O vibration peak 1050 cm 1 belong to glucose precursor decrease other wise C O and C C vibration peaks 1695 and 1610 cm 1 are domi nantly seen to the HTC structure 26 27 This result indicates that via the HTC process sp3 C O bands have converted to the sp2 C C and C O bands 28 The same result was also seen on Fig 2 too When the FTIR spectra of HTC and HTC were compared since the amount of oxygen atoms decreased after the calcination process C C bands were seen dominantly 3 2 Characterization of microstructure Microstructures of samples are presented in Fig 3 HTC reinforced samples contained pearlite and ferrite phases Percentages of ferrite Fig 3 Microstructure images of a pure iron b Iron 0 25 HTC c Iron 0 50 HTC d Iron 0 75 HTC e Iron 0 25 HTC f Iron 0 50 HTC and g Iron 0 75 HTC H Simsir et al Materials Chemistry and Physics 242 2020 122557 4 and pearlite ratios were calculated by the systematic point counting method 29 Grain boundaries can be clearly seen for all samples The mean linear intercept method was used to determine grain sizes of specimens on optical micrographs 29 30 While the increasing of HTC amount caused to increase the pearlite phases amount grain sizes of composites were reduced The same trend was observed for HTC reinforced composites However HTC reinforced composites have smaller grain sizes and higher pearlite than HTC reinforced compos ites This is because HTC has higher carbon content than that of HTC Since the increasing of carbon content lead to increment of cementite Table 1 Microstructural and mechanical properties of samples Specimen Grain Size m Pearlite Relative Density Porosity Hardness Hv UCSa MPa Pure Iron 42 93 4 4 98 75 1 25 57 1 3 788 Iron 0 25 HTC 31 34 3 7 9 75 98 74 1 26 61 1 6 844 Iron 0 50 HTC 25 92 2 6 18 61 98 55 1 45 75 2 3 883 Iron 0 75 HTC 23 07 2 7 35 95 98 50 1 50 83 2 8 970 Iron 0 25 HTC 27 38 2 9 15 42 98 78 1 22 71 1 9 855 Iron 0 50 HTC 24 07 3 1 31 11 98 27 1 73 80 2 1 945 Iron 0 75 HTC 21 59 2 7 42 19 98 22 1 78 103 3 2 1028 a Ultimate Compression Strength Fig 4 SEM analysis of Iron 0 5 HTC a SEM image b EDX mass percentage analysis and c EDX line analysis Fig 5 X ray diffraction patterns of a Iron HTC and b Iron HTC composites H Simsir et al Materials Chemistry and Physics 242 2020 122557 5 volume ratio therefore smaller grain sizes and higher pearlite was occurred 14 31 Microstructural and mechanical properties of samples were given in Table 1 Since Iron 0 75 HTC possessed the highest carbon content it contained the highest pearlite phase amount which was nearly 42 more than that of pure iron But the smallest average grain size with 21 59 m occurred on this composite However it possessed also the highest porosity value due to higher reinforcement amount While pure iron possessed 1 25 porosity Iron 0 75 HTC possessed 1 77 porosity Differentiation between theoretical and experimental density derived from neglectable failing of samples production during com pacting and sintering processes Table S1 32 SEM EDX analysis of Iron 0 5 HTC was presented in Fig 4 It can be seen that there were some micropores on the microstructure of samples Especially these pores occurred near the grain boundaries According to previous studies porosity has negatively effective on me chanical properties generally 12 14 However when these pores are located close to grain boundaries they do not significant effect on me chanical properties of composites 12 Also it could be said that inside the grains and grain boundaries oxidation degree steadied to minimum level according to SEM EDX analysis Due to occurrence of cementite phases which composed of Fe3C in pearlite phase point 1 higher carbon amount than ferrite phase point 2 was detected The X ray diffraction patterns of pure iron HTC HTC and HTC HTC reinforced composites are shown in Fig 5 Even if the calcination process caused to increase in carbon content of HTC the crystalline structure did not occur since they are formed amorphous structure 33 In addition to this few amounts of HTC or HTC were added on the iron matrix Because of these reasons any changes could not be detected on HTC HTC reinforced irons by XRD results But carbon content of composites was seen on SEM and SEM EDX analysis which mentioned above All composite samples possessed the same peaks 2 44 65 and 820 with pure iron sample JCPDS 65 4899 34 3 3 Characterization of mechanical properties and corrosion behavior As mentioned above the increase in carbon content led to smaller grain sizes and higher percentage of pearlite Smaller grain sizes and higher percentage of pearlite lead to increase of hardness Because smaller grain sizes lead to restriction of dislocation movement and perlite phases contain cementite phases which is harder than ferrite phases The same trend was also observed for ultimate compression strength UCS of samples Fig 6 As shown in Table 1 the hardness of pure iron raised to 103 3 2 Hv and the UCS value raised at 1028 MPa with the addition of 0 75 wt HTC Due to the calcination process HTC was contained higher car bon amount than HTC Therefore HTC was more effective on the increment of mechanical properties than HTC To sum up the increase of hardness and UCS of samples can be explained by the following reasons Dislocation movement can be restricted due to the increase of HTC HTC amount Thus Orowan looping mechanism maybe occurred 15 This mechanism claimed that with the addition of carbona ceous additives in metal matrix caused to occurrence of residual dislocation loops around the carbonaceous additives 15 35 Fig 6 Compression test graphs of prepared samples Fig 7 Potentio dynamic polarization curves of a Iron HTC and b Iron HTC composites Table 2 Corrosion results of prepared samples Specimen Ecorr V Corrosion Current Density mA cm2 Corrosion Rate mm year Pure Iron 0 42 0 122 0 94 Iron 0 25 HTC 0 38 0 111 0 85 Iron 0 50 HTC 0 41 0 106 0 81 Iron 0 75 HTC 0 44 0 242 1 85 Iron 0 25 HTC 0 48 0 066 0 50 Iron 0 50 HTC 0 47 0 146 1 12 Iron 0 75 HTC 0 35 0 298 2 28 H Simsir et al Materials Chemistry and Physics 242 2020 122557 6 Increasing of HTC HTC amount causes to obtain smaller grain sizes Therefore one can be concluded that increasing mechanical prop erties is related to the Hall Petch strengthening mechanism 36 The increasing of HTC HTC content the amount of cementite phase in the structure increased Therefore increasing of cementite phase which is harder than matrix led to the enhancement of mechanical properties This mechanism is called as Halpin Tsai model 37 In Fig 7 potentiodynamic polarization curves with extrapolated from Tafel slopes of samples are shown Corrosion potentials Ecorr corrosion currents corrosion current densities Icorr and corrosion rates have been listed in Table 2 Corrosion rates of all prepared samples were calculated according to ASTM G102 89 2015 E1 standard 38 With the addition of a low amount of HTC 0 25 0 50 wt into pure iron corrosion rates decreased Table 2 During the corrosion process iron iron carbon products were oxidized and other oxidized compounds such as FeOOH Fe3O4 and Fe2O3 formed due to the alteration of pH ions Cl SO4 2 and CO3 2 alloying elements 39 41 These layers could reveal passivating or corroding effect against to corrosion solu tion depend on kinetic and thermodynamic factors 40 Corrosion of iron based materials has begun with the oxidizing of iron at the anode to form Fe 2 ions and reduction of dissolved oxygen at the cathode to form OH ions Then they were combined to iron II hydroxide solid Eqs 3 5 42 Fe Fe 2 2e 3 2H2O 2e H2 2OH 4 Fe 2 2OH Fe OH 2 s 5 Fig 8 SEM images after the corrosion tests a pure iron b Iron 0 25 HTC c Iron 0 50 HTC and d Iron 0 25 HTC Fig 9 SEM images after the corrosion tests a Iron 0 75 HTC b Iron 0 50 HTC c and d Iron 0 75 HTC H Simsir et al Materials Chemistry and Physics 242 2020 122557 7 With the further aging FeOOH and Fe3O4 formed according to Equa tions 6 and 7 42 43 3Fe OH 2 s Fe3O4 2H 6 4Fe OH 2 O2 4 FeOOH 2H2O 7 It is claimed that these oxidized layers which formed with the using of the low amount of HTC protected the composite against to corrosive solution and it caused the decreasing of the corrosion rates 40 This result in a good agreement with the SEM images of samples taken from after the corrosion test Fig 8 It was seen that the surface of these materials was coated by iron oxide compounds which were proved by EDX analysis Fig S1 Also with the using of 0 25 wt HTC inside the iron matrix the lowest corrosion rate was obtained On the other hand with the increasing of HTC or HTC amount 0 50 0 75 wt corrosion rates were significantly increased Table 2 The reason for it was understood by SEM analysis After the corrosion test some crevices were obviously seen on samples surface especially on ferrite phases Fig 9 It is know from literature even if these pro tective oxidized layer decrease the corrosion rate eventually these layers were deteriorated by NaCl corrosive solution with following re actions 43 Fe 2 2NaCl 2OH FeCl2 2NaOH 8 FeCl2 1 4 O2 5 2