Cr2O3 Particles Research Articles

Microstructural characteristics of the internal oxidation zone of ferritic/martensitic steel exposed to LBE at 550°C for 1000 h

The oxidation products formed on ferritic/martensitic (F/M) steel exposed to oxygen-saturated lead-bismuth eutectic (LBE) at 550 °C for 1000 h were investigated using various characterizations. The results indicate that the corrosion products consist of three distinct layers from the inside to the outside: the inner oxidation zone (IOZ), a middle oxide layer, and the growth front facing LBE. In the IOZ, although O has penetrated the entire oxidation layer, the martensite laths and ferrite grains remain visible. However, significant segregation of Cr and O along the laths and grain boundaries has occurred, resulting in the formation of strip-shaped Cr2O3 particles. In the matrix adjacent to the IOZ, Cr atoms have segregated at the grain boundaries and martensite laths, forming Cr-rich regions, while O atoms have not yet infiltrated. During the growth of Fe3O4 grains, the priority formed strip-shaped Cr2O3 particles are pushed toward the corrosion front until they detach from the F/M steel and disperse into the LBE, resulting in nearly pure Fe3O4 grains in the middle layer. The gradient three-layer structure of the oxidation product is closely associated with the segregation of Cr and the gradient distribution of oxygen partial pressure (PO2).

Initial stage oxidation corrosion of commercial ferritic stainless steels with different Cr contents at 650 °C for solid oxide fuel cells

Selecting adequate ferritic stainless steel (FSS) with a high corrosion resistance and a low cost is critical for solid oxide fuel cells (SOFCs) operating at intermediate temperature. In this study, the corrosion behaviors of four commercial FSSs involving TS430, TY441, YG442, and TY445 with a Cr content ranging from 16.18 wt.% to 21.73 wt.% are investigated at 650 °C. The oxidation mass gains, microstructures of surface oxide scale, and electrical conductivities are measured. The effects of grain size as well as doped elements are estimated together with the Cr volatilization. Flaky Cr2O3 particles are formed on TS430 and TY441 dominated by the outward migration of Cr3+. In comparison, a thin and dense layer of chromia is observed on YG442 and TY445. A high Cr content and a uniformly distributed grain size are conducive to the formation of a thin and dense chromia scale on the FSS surface during the initial oxidation process. On the other hand, the addition of Nb, Ti, and Mo weakens the outward diffusion of Cr3+ and reduces the particle size of chromia. After oxidation at 650 °C for 120 h, scattered (Mn, Cr)3O4 spinel particles occur on TS430, YG442, and TY445. TY445 and YG442 exhibit a higher conductivity although all the results of area specific resistance (ASR) are less than 6 mΩ·cm2. Meanwhile, the effect of Cr volatilization is enlarged on the estimation of mass gain at 650 °C compared with even higher temperatures.

Effects of Al2O3 and Cr2O3 on the microstructure and properties of Mo alloys prepared via vacuum sintering

The dilemma of strength and ductility of Mo alloy at ultra-high temperature (above 1300 °C) limits its application in space reactors and other high-temperature environments. Single oxide enhancement has been unable to meet these use requirements. In this research, a strategy of synergistic reinforcement of Mo alloys with nanosized Al2O3 and Cr2O3 ceramic particles was proposed. A 300−400 nm Mo alloy powder was prepared by liquid‒solid doping, and in situ self-generated nanosized oxides were obtained. The grain size of vacuum sintered Mo alloy was very fine, at only 5.3 μm, which was one tenth of the particle size of commercial Mo alloy. Al2O3 and Cr2O3 particles were distributed in the grains of the Mo matrix, which effectively prevented the growth of Mo grains during vacuum sintering and reinforced the Mo alloy. The maximum flow stress of the Mo–Al2O3–Cr2O3 alloy reached 367 MPa at 1000 °C/1 s−1, which was better than that of the single-oxide reinforcement. The ultimate tensile strength (UTS) of the Mo–Al2O3–Cr2O3 alloy was 862 MPa, which was twice that of pure Mo. The preparation process is simple and available for industrial production. Synergistic strengthening of multiple oxides will be the best strategy for strengthening refractory alloys in the future.

A comparative study on anisotropy of additively manufactured CoCrNi medium-entropy alloys by hot isostatic pressing and ultrasonic impact treatment

The anisotropy properties of samples in different direction is found in additively manufactured (AM) CoCrNi medium-entropy alloys (MEAs). In this study, the laser direct energy deposition AM CoCrNi MEAs have been subjected to two alternative processing methods: hot isostatic pressing (HIP) and ultrasonic impact treatment (UIT). The effect of HIP and UIT on the microstructure, grain orientation, grain boundary distribution, phase distribution and mechanical properties of AM CoCrNi MEAs were systematically studied. The results show that HIP decreased the partial mechanical anisotropy of AM CoCrNi MEAs, and YS was significantly reduced. The main reason is that the HIP induces the formation of large number of Cr2O3 particles, and transformation of low-angle grain boundaries (LAGBs) into high-angle grain boundaries (HAGBs). Surprisingly, both the yield strength (YS) and ultimate tensile strength (UTS) of the AM CoCrNi MEAs were increased when the UIT was added after every laser deposition of one layer (UIT-1). This is due to the combined effect of quasi-static loading and ultrasonic oscillations of UIT, which results in the dislocation multiplication and the formation of a large number of substructures. In addition, the above strengthening phenomena also lead to decrease partial mechanical anisotropy of AM CoCrNi MEAs.

Eutectoid decompositions in Ce-containing ABO3 perovskites: Part II, the case of divorced growth in CeCrO3.

A eutectoid phase transformation was exhibited by the perovskite CeCrO3 when heated in air. The kinetics of the reaction, microstructure of the product, and mechanisms of the transformation were studied using thermogravimetric analysis, X-ray and Raman spectroscopy, X-ray diffraction, and electron microscopy. Fluorite CeO2 and corundum Cr2O3 were formed from the decomposition of CeCrO3. The CeO2 particles were porous and polycrystalline, a consequence of nucleation, growth, and impingent of CeO2 domains on the CeCrO3 particles. Anisotropic growth is indicated by the morphology of the CeO2 grains, while the Cr2O3 particles were single crystals without any crystallographic orientation relationship to the parent phase. Unlike the CeAlO3 eutectoid, the microstructure comprised of CeO2 and Cr2O3 show no characteristics of a microstructure formed by cooperative growth. The disparity between the eutectoid reactions in CeCrO3 and CeAlO3 is attributed to a difference in interfacial energy between the fluorite and sesquioxide phases (i.e., CeO2/Al2O3 versus CeO2/Cr2O3).

High-temperature oxidation behavior of a 9Cr oxide dispersion strengthened alloy under limited oxygen condition

Hot compression bonding is a promising process to fabricate large-scale oxide dispersion strengthened alloys. Inevitable interface oxidation could affect the effectiveness of the joint. The high-temperature oxidation behavior of a 9Cr ODS alloy under limited oxygen condition was investigated. The oxidized surface consisted of inner Fe2O3 scale and outer Cr2O3 particles at 800 °C. Reoxidation at 1000 °C, Cr2O3 particles were decomposed and converted into Cr(Ti)O2. With increasing oxidation time, Fe2O3 and Cr(Ti)O2 were decomposed and Y2O3 pegs formed. Furthermore, TiO2, Y2O3 and Y-Ti-O nanoparticles formed along grain boundaries. In conclusion, the oxide evolution could be summarized as Fe2O3→Cr2O3→Cr(Ti)O2→TiO2→Y2O3→Y-Ti-O nanoparticles. The evolution from initial coarse Cr-rich and Fe-rich oxides to fine Y-Ti-O nanoparticles is expected to be critical for hot compression bonding processes.

Enhancing oxidation resistance of ferritic heat-resistant stainless steel in air atmosphere at 1100 °C by self-repairing oxide layer

The oxidation behaviors of Al-free and 1Al ferritic heat-resistant stainless steels (FHSSs) at 1100 °C were investigated. After oxidation for 100 h, the Al-free FHSS had triple oxide layers of a first layer Fe2O3 + MnCr2O4, a second layer MnCr2O4 + Cr2O3 + MnO, a third layer SiO2 and oxides of Nb and Ti. The 1Al FHSS had double oxide layers of a first layer Ti-bearing (Al, Cr)2O3 particles, a second layer dense (Al, Cr)2O3. The (Al, Cr)2O3 layer with self-repairing feature can reduce the thickness of oxide layer by 515 times, and reduce the oxidation weight gain rate of the FHSS by 5 orders of magnitude.

Mechanism and property optimization of stainless steel slag for preparation of cementitious materials

The effective utilization of stainless steel slag on a large scale has posed a persistent challenge. To address this problem, this study used the orthogonal test method to investigate the optimisation of the ratio of stainless steel slag preparation cementitious materials while exploring the curing mechanism of metallurgical solid waste materials and its stability and the leaching of heavy metals. The experimental results revealed that the optimal combination consisted of 59% granulated blast furnace slag(GBFS), 35% stainless steel slag(AODS), and 6% desulfurization gypsum(DG). This composition yielded impressive compressive strength values of 11.40 MPa at 3 days and 28.36 MPa at 28 days. The stainless steel slag(AODS) contains a large amount of highly reactive calcium-containing material, accelerating the hydration reaction for 7–28 days. Moreover, the 3CaO·2SiO2·3 H2O(C-S-H) dense layered structure and related products produced by the hydration reaction can effectively encapsulate the Cr2O3 particles. As a result, the strength, stability and safety of the cementitious materials were significantly improved.

Effect of irradiation damage defects on the impurity containing molten salt corrosion behavior in GH3535 alloy

This study explores the corrosion response of irradiated nickel-based GH3535 alloy in impurity-enriched molten FLiNaK salt at 650 °C. Displacement damage resulting from Au ion irradiation formats dislocation loops, whose distribution is influenced by subsequent He ion irradiation and He bubble formation. Samples irradiated with Au ions exhibit a shallow corrosion layer with big-size and dense distributed Cr2O3 particles, while a contrasting trend is observed in samples irradiated with He ions. Displacement damage decelerates Cr outward diffusion by promoting protective Cr2O3 formation with SO42- impurities, thereby inhibiting impurity-accelerated corrosion. However, the accelerating effect of He bubbles subsequently counteracts this inhibitory impact on corrosion.

A SP-ICP-MS protocol for the detection of metal nanoparticles composition and size in tattooed ex vivo human skin explants

We developed and validated a protocol based on Single Particle Inductively Coupled Plasma Mass Spectrometry (SP ICP-MS) to detect composition and size of metal nanoparticles (MNPs) in tattoo inks end ex vivo tattooed human skin explants. The explants were tattooed with different inks using an ordinary tattoo machine. Then, 72 hours after tattooing, skin explants were subjected to alkaline extraction by tetramethylammonium hydroxide solution and MNPs of Ag, Al2O3, Au, Cr2O3, CuO, Fe2O3, TiO2 and ZnO were analysed for particle composition and size by SP ICP-MS. The method was validated by assessing the limit of detection, accuracy, precision, and size stability over 72 hours. Particles of Al2O3, Cr2O3, CuO, Fe2O3, TiO2 and ZnO were observed in human skin in the range from 27 nm to 153 nm, and from 26 nm to 228 nm in tattoo inks. Ag and Au NPs were not found neither in inks nor in the skin. Advantages of the protocol were the ability to simultaneously detect the composition of particles and their size, the straightforward sample preparation, the high sensitivity and precision, and the speed of execution of the analysis. The developed methodology can be applied to skin exposed to other consumer products topically applied, such as sunscreens, cosmetics, personal care products and medical devices, which can be all sources of MNPs, in order to improve knowledge and support the human exposure assessment process.

Investigation of The Effect of Cr2O3 Particles on Al-Si Matrix Composites Produced by Powder Metallurgy

Metal matrix composite materials can be produced by powder metallurgy method. In this study, composite material with Al+12wt%Si matrix was produced by powder metallurgy (P/M) method. Al+12wt%Si powder was mixed by adding 5wt%, 10wt% and 15wt% Cr2O3 powder. Al+12wt%Si + Cr2O3 mixture powders were pressed unidirectional with 500MPa pressure in a cylindrical mold and sintered at 500 ºC. After sintering, optical microstructure, Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS) and microhardness analyzes of the samples were made. When the results were examined, it was observed that a porous structure was formed in all of the samples. Moreover, the lowest amount of microhardness was measured in the sample added %15wt Cr2O3 powder sintered at 500 ºC.

A novel Cr2O3 coated CNTs system: Synthesis, microstructure regulation, and characterization

Surface modification is an attractive strategy for expanding, improving, or altering the properties and functions of carbon nanotubes (CNTs), which opens up a broad range of novel applications. Herein, a simple, and efficient approach for the synthesis of the Cr2O3 coated CNTs system was developed, and the morphologies and microstructures of the coating on CNTs along with annealing temperature were systematically investigated. It was found the continuous amorphous (Cr2O3)1/2·(H2O)3/2 coating with a thickness of about 3–4 nm can be decorated onto CNTs with the applied coating processes, and which can be transformed into continuous amorphous Cr2O3 coating after annealing at 500 °C for 0.5 h. With further increasing the annealing temperature to 700 °C, nano Cr2O3 particles with high crystallinity were formed at the expense of amorphous Cr2O3 coating, and the coating on the surface of CNTs can be completely consumed for transforming into crystalline Cr2O3 nanoparticles when the annealing temperature is up to 800 °C. The findings provide important guidance for the surface modification of CNTs and lay the foundation for the industrial application of the novel Cr2O3 coated CNTs.

Evaluation of Corrosion Resistance and Surface Film Analysis after Corrosion Testing of Materials Coated by Chemical Densified Coating Method under Boiling Sulfuric Acid Environment

For the purpose of developing metallic materials with excellent corrosion resistance under boiling sulfuric acid environment, the coated materials were evaluated for their corrosion resistance and the differences in surface morphology were investigated. As a result, the corrosion resistance of SUS304 coated and sintered eight times by chemical densified coating method (S-ZAC) was maintained at the point after 12h corrosion test, but the corrosion rate rapidly increased after 100h corrosion test. The cross-sectional microstructural analysis of the specimens showed that only a small amount of SiO2 remained on the surface, while Cr2O3 completely disappeared. The mechanism of film delamination in S-ZAC is assumed to be due to the thermal expansion caused by heating, which resulted in curvature of the thick film and cracks at the Cr2O3 and SiO2 interfaces. On the other hand, SUS304 coated with higher density of Cr2O3 by repeating the coating and sintering eleven times (MS-ZAC) showed excellent corrosion resistance as well as SiC even after 100h corrosion test. The results of cross-sectional microstructural analysis showed that MS-ZAC had higher Cr2O3 concentration, finer SiO2 grain size, and fewer porosity than S-ZAC. In particular, the mechanism of film maintenance in MS-ZAC is assumed to be the formation of a stacked structure in Cr2O3 particle layer, in addition to the thinning of the entire film.

Influence of oxygen on performance of multi-principal element alloy as braze filler for Ni-base alloys

In manufacturing of multi-principal element alloys (MPEAs), the casting process is often a primary point of oxygen introduction to the material system, which was demonstrated by the laboratory scale button arc-melting process. Oxygen introduction raises concerns for the mechanical performance of these alloys if employed as structural materials alone or in engineering applications, such as serving as filler materials to enable joining of similar or dissimilar alloy pairs that are conventionally considered difficult to join. In this work, oxide inclusions in an as-cast off-equiatomic MnFeCoNiCu MPEA and Ni-base alloy braze joints made with this MPEA were evaluated by synchrotron x-ray diffraction mapping and electron microscopy. MnO was found to be prevalent throughout the cast MPEA and was chemically reduced during brazing by trace Al from the base material, Ni-base Alloy 600. Incomplete reaction of the MnO with Al, and some alternative reaction with Cr, left a mixture of MnO, Al2O3, and Cr2O3 in the as-brazed joint, with the oxides concentrated near the braze centerline due to directional solidification. In the braze joints, the non-oxide constituent phases detected were an FCC matrix and particles of Cr23C6, Cr7C3, and TiN which are all native to Alloy 600. The evolution of oxides within the brazed joints at elevated service temperatures of 600–800 °C was also evaluated. While MnO and Al2O3 were stable during high-temperature service, Cr2O3 particles grew to several hundred microns, with dissolved oxygen in the MPEA providing a significant source for oxide growth. Comparing tensile performance of the as-brazed condition with post-service conditions showed that the evolution of oxide particles contributed to an increase in strength and decrease in ductility of the brazed joints. Evaluating particle morphologies among fracture surfaces of individual specimens demonstrated that large Cr2O3 particles and continuous cluster networks of Al2O3 were the features most detrimental to total elongation. Hence, unmitigated evolution of oxygen-containing species during brazing and service conditions is detrimental to the ductility of the brazed joints, which highlights the importance of oxygen control in initial manufacturing of MPEAs for engineering applications.

Fabrication and high-temperature tribological behaviors of Al2O3/Cr2O3 composites with three-dimensional continuous structure

A new strategy for improving high-temperature compressive strength and tribological properties of Al2O3/Cr2O3 composites was proposed in this study. The three-dimensional (3D) continuous Al2O3 ceramic matrix containing Cr2O3 particles was fabricated, and the influencing mechanisms of compositions and structures on the anti-wear and friction-reducing performance of composites at high temperature were revealed. Results show that the enrichment degree of Cr2O3 in the composites can be significantly improved based on the 3D continuous structure design compared with Al2O3/Cr2O3 composite containing uniform compositions. Under friction conditions, the Cr2O3 phase with large enrichment degree can preferentially contact with the micro-asperities on the friction pair surface under the action of grain refinement at high temperature, so that the softened Cr2O3 is easy to be sheared and dragged to the worn surfaces of the frictioncouples to form the friction film and transfer film. Meanwhile, under the favorable effect of the high load-carrying capacity of continuous Al2O3 matrix, Al2O3/Cr2O3 composites show excellent tribological properties at high temperature. The friction coefficient and wear rate of Al2O3/Cr2O3 composites with 3D continuous structure sliding against Al2O3 pin can be reduced to 0.35 and 2.2 × 10-6 mm3·N-1m−1 at 800 °C, and it still presents excellent friction-reducing and anti-wear properties at 1000 °C.

Investigation on the corrosion behavior of Alloy 800H at various levels of deformation

The corrosion behavior of Alloy 800H in deaerated supercritical water was investigated. Multi-pass cold rolling was used to achieve thickness reductions of up to 80%, and the weight gain vs. time (up to 1000 h) in supercritical water at 600 ℃ and 25 MPa were obtained for specimens in the polished vs. ground surface condition. Polished specimens without rolling showed the highest corrosion rates, and surface grinding or cold rolling significantly increased the corrosion resistance. A thick oxide film develops, with an outer moderately uniform layer of magnetite (Fe3O4) with crystallites along the surface, and areas of uneven oxidation into the metal that incorporate Cr (e.g., FeCr2O4). Very few Cr2O3 particles exist, and preferentially near the grain boundaries. Continuous Cr-rich oxide films were found in the thin oxide films on the surface of ground specimens and heavily rolled specimens, and an associated Cr depleted zone in the metal under the oxide of ground specimens, but not in heavily rolled specimens. This indicates that the high density of dislocations accelerates the diffusion of elements and enhance the formation of Cr-rich oxide film, which promotes passivity.

Bionic coating imitating reflection characteristics of plant leaf in solar spectrum waveband for hyperspectral camouflage

Imitating the reflection characteristics of plant leaves in solar spectrum waveband with bionic coatings can effectively counter the hyperspectral detection technology in the vegetation background. Herein, inspired by the formation mechanisms of the reflection characteristics of plant leaves, a bionic coating containing chromium oxide (Cr2O3) particles and a hydrophilic inorganic salt dispersed in a polyvinyl alcohol (PVA) matrix is prepared on metal plates, and a theoretical model was constructed to clarify the bionic mechanisms. Results show that the Cr2O3 particles exhibit absorption characteristics similar to those of chlorophyll and scattering characteristics similar to those of multilayer cells in plant leaves, thereby enabling the bionic coating to imitate the reflection characteristics in the visible and near-infrared waveband. Meanwhile, the hydrophilic inorganic salt can absorb moisture molecules in the air when the bionic coating is placed in natural environments, thereby absorbing incident radiation and imitating the water absorption valleys. Moreover, it was found that there is only non-freezing bound water in the bionic coating with a differential scanning calorimeter, thus the moisture absorption processes associated with the hydrophilic hydroxyl groups in PVA matrix were considered when determining the mass transfer characteristics in a natural environment. In the whole solar spectrum, the bionic coating can significantly suppress the high reflectance of the metal plates when the volume fraction of Cr2O3 particles is 0.81 % and the coating thickness is greater than 0.2 mm. Increasing the surface roughness of the metal plates can further improve the suppressing performance in the range from 800 to 1300 nm, achieving a better similarity of the reflection curves between the bionic coating and the plant leaves. The outstanding imitation performance of the key reflection characteristics of the plant leaves confirms the remarkable application potential of the bionic coating in the field of hyperspectral camouflage.

Human biomonitoring and personal air monitoring. An integrated approach to assess exposure of stainless-steel welders to metal-oxide nanoparticles

In welding, there is a potential risk due to metal-oxide nanoparticles (MONPs) exposure of workers. To investigate this possibility, the diameter and number particles concentration of MONPs were evaluated in different biological matrices and in personal air samples collected from 18 stainless-steel welders and 15 unexposed administrative employees engaged in two Italian mechanical engineering Companies. Exhaled breath condensate (EBC) and urine were sampled at pre-shift on 1st day and post-shift on 5th day of the workweek, while plasma and inhalable particulate matter (IPM) at post-shift on 5th day and analysed using the Single Particle Mass Spectrometry (SP-ICP-MS) technique to assess possible exposure to Cr2O3, Mn3O4 and NiO nanoparticles (NPs) in welders. The NPs in IPM at both Companies presented a multi-oxide composition consisting of Cr2O3 (median, 871,574 particles/m3; 70 nm), Mn3O4 (median, 713,481 particles/m3; 92 nm) and NiO (median, 369,324 particles/m3; 55 nm). The EBC of welders at both Companies showed Cr2O3 NPs median concentration significantly higher at post-shift (64,645 particles/mL; 55 nm) than at pre-shift (15,836 particles/mL; 58 nm). Significantly lower Cr2O3 NPs median concentration and size (7762 particles/mL; 44 nm) were observed in plasma compared to EBC of welders. At one Company, NiO NPs median concentration in EBC (22,000 particles/mL; 65 nm) and plasma (8248 particles/mL; 37 nm) were detected only at post-shift. No particles of Cr2O3, Mn3O4 and NiO were detected in urine of welders at both Companies. The combined analyses of biological matrices and air samples were a valid approach to investigate both internal and external exposure of welding workers to MONPs. Overall, results may inform suitable risk assessment and management procedures in welding operations.

A Single Layer of Chromium Oxide Nanoparticles Films Coated with Carbon by Applying Exploding Wire Technique for Efficient Solar Selective Absorber

The efficiency of solar energy absorption in solar heaters is increased by the use of selective absorption coating that possesses high absorption of solar radiation in the UV-visible spectrum as well as low emission at the operating temperature in the infrared region. In this work, novel selective coatings were synthesized by improving the selectivity of chromium oxide (Cr2O3) nanoparticles by doping with carbon nanoparticles using the exploding wire technique for carbon rods by high current in suspended Cr2O3 particles. The structural properties and surface topography were studied by XRD and FE-SEM, which illustrate the carbon-coated Cr2O3 nanoparticles. The prepared nanoparticles were mixed with a support material, Polyvinyl pyrrolidone (PVP) as a matrix, for use as a selective coating for three metals, namely copper, aluminium and stainless steel (SST). Reflectivity measurements were performed within the UV-Visible spectrum to calculate the absorption of solar radiation using numerical integration. The reflectivity was also measured in the range from 2.5 to 25 μm to calculate the thermal emission of the solar heater within the proposed operating temperature of 373 K. The measurements showed good efficiency of using the produced material as a selective coating which was prepared in a simple way compared to conventional methods. The best sample with efficient absorptance (α) for solar spectrum and of lowest emittance (ε) in IR region was for Al substrate coated by Cr2O3:C:PVP of α =0.886 and ε= 0.260.

Detailed insight into chromium species released from failed CoCrMo implants: Ex vivo periprosthetic tissues study.

This unique study provides information on Cr species and their distribution in periprosthetic tissues of patients with metal-on-polyethylene joint implants. Co-Cr-Mo alloy has been widely used in joint replacement and represents a source of metal derived species. In the case of chromium, previous studies on periprosthetic tissues revealed mainly Cr(III) distribution, whereas the potential release of carcinogenic Cr(VI) species has been still a subject of debate. Here, an analytical approach utilizing speciation and fractionation was developed to analyze periprosthetic tissue samples collected from wide range of patients with failed total hip or knee replacements. The results reveal that Cr(III) is mainly released in the form of insoluble CrPO4 and Cr2 O3 particles. The highest Cr contents were found in periprosthetic tissues of patients suffering from aseptic loosening and having more Cr-based implants in the body. Cr species penetrated tissue layers, but their levels decreased with the distance from an implant. The detailed speciation/fractionation study carried out using the set of consecutive periprosthetic tissues of a patient with extensive metallosis showed the presence of trace amounts of free Cr(III), nanoparticles, and metal-protein complexes, but the majority of Cr still occurred in CrPO4 form. Carcinogenic Cr(VI) species were not detected. Up to date, there is no published human tissue study focused on the detailed speciation of both soluble and insoluble Cr-based species in the context of failing total hip and knee replacements.