Indentation Hardness Research Articles

Properties of Ni-B/B Composite Coatings Produced by Chemical Reduction

The paper presents the results of research on composite Ni-B coatings with embedded particles of boron produced by a chemical reduction method and their influence on the mechanical, tribological, and corrosion properties of produced materials. Boron was used in two forms: an alloy component and nanoparticles incorporated into the Ni-B matrix. The coatings were deposited from a bath at different concentrations of dispersion phase. The paper also presents the characteristics of the used boron particles. Results of morphology and surface topography (SEM) as well as the structure (XRD) of the produced coatings are presented. The mechanical properties of the produced coatings, like Knoop hardness, Martens hardness, and indentation hardness, as well as the modulus of elasticity, were determined. The tribological tests were carried out using the ball-on-disc method. Electrochemical corrosion tests were conducted by the potentiodynamic method. The adhesion of the coatings to the substrate was evaluated by the scratch test method. Consequently, this investigation yielded a novel material in the form of Ni-B/B composite coatings, exhibiting significantly improved mechanical and tribological properties compared to Ni-B coatings without embedded particles of the dispersion phase.

Enhanced Morphological, Mechanical and Dielectric Properties of Paraffin Wax Incorporated with Polyaniline (PANI) and Reduced Graphene Oxide (RGO) nanocomposites

In the present work, composites of polyaniline (PANI)/Paraffin and PANI/reduced graphene oxide (RGO)/Paraffin have been evaluated for mechanical properties by nanoindentation technique and electrical and dielectric properties by open-ended coaxial probe technique. For mechanical tests, the 5 mm thick composites have been subjected to a maximum load of 296.9 μN and the deformation has been recorded for the composites throughout the loading-unloading mechanisms of the Berkovich indenter. PANI/Paraffin composites yield higher deformation of 717.2 nm while the lowest displacement has been exhibited by PANI/RGO/Paraffin composites of 484.7 nm with distinct elastic recovery of the material. In terms of indentation Hardness and Young's modulus, PANI/RGO/Paraffin composites reveal higher hardness of 0.034 GPa and Young's modulus of 3.5 GPa. To study the electrical conductivity and dielectric properties of the composites over the X band frequency range (8–12 GHz), the composites have been coated with a layer of gold nanoparticles by sputter coating technique. Gold coated PANI/RGO/Paraffin composites shows enhanced electrical conductivity which is 54 % higher as compared to gold coated pure PANI/Paraffin composite at a frequency of 12 GHz. Also the dielectric properties are seen to have improved for PANI/RGO/Paraffin composites.

Strong yet ductile self-passivating W-10Cr alloy by laser powder bed fusion

Compared to pure tungsten, self-passivating tungsten alloys (SPTAs) for the future nuclear fusion armour are expected to offer a major safety guarantee in a loss-of-coolant accident (LOCA) event. Here we used laser powder bed fusion (LPBF) to print a self-passivating W-10Cr system. The main challenges for processing W-10Cr alloys are balling phenomena and chromium loss due to their melting point differences. After laser parameters optimizations, W-10Cr blocks with relatively dense and smooth surface were fabricated. As-built specimens exhibited an inhomogeneous microstructure with W-rich regions and Cr-rich ones. In the Cr-rich region, ultrafine equiaxed grains were obtained in view of Spinodal decomposition. Owing to the co-contribution of Spinodal decomposition and fine-grain structure, the compressive strength, fracture strain and Vickers hardness (HV0.005) of W-10Cr alloy reach 1451 MPa, 21.5% and 9.4 GPa, which are obviously superior to pure tungsten counterparts, with the improvement of 41%, 115% and 43%, respectively. Based on the indentation responses, as-measured indentation hardness followed typical indentation size effect (ISE). A higher contribution from elastically surface work in the early part of indentation is responsible for the hardening mechanism of W-10Cr alloy. Additionally, the strengthening and toughening mechanisms associated with improved properties are also discussed. The mechanistic insights into the deformation behavior have extensive implications for the development of additively manufactured SPTAs with exceptional mechanical properties.

Nabataean iron picks for copper mining from Nahal ‘Amram, Israel; Chemical, isotopic and production technology analysis

Recent excavations at Naḥal ‘Amram, a Nabataean copper mining center in the Arabah valley, Israel, unearthed for the first time four iron tips of mining picks. The present study undertakes a complex investigation of the picks, including metallographic, indentation hardness, slag inclusions (SIs), metal matrix, and osmium isotopic composition (Os-IC) analyses. The results indicate that the picks were manufactured via similar blacksmithing techniques, using two types of hard alloys: quench-hardened steel and phosphoric iron. A correlation was found between the composition of SIs, metal, and osmium isotopic signature, suggesting that three different ore sources were exploited to produce these picks. The quenched steel likely originated from a single ore source, whereas the two P-rich iron probably provenance from two different, yet geographically close or geologically similar ore deposits.The undertaken study highlights the importance of an integrative provenancing approach, which relies on the analyses of siderophile/chalcophile elements of the metal, lithophile trace elements of slag inclusions, and osmium isotopic analyses. This approach allows the complete characterization of the ore provenance signature of an artefact. However, the final provenance assignment to a specific ore deposit is currently limited, as it depends on our knowledge and familiarity with potential ore sources and on the archaeological evidence of their exploitation.

Effects of Nitrogen Modification of Porous PVD–MoS2 Coatings on the Tribological Behavior under Rolling–Sliding Conditions in Vacuum

In order to improve the tribological performance of PVD–MoS2 coatings, which are frequently used as a solid lubricant for operating in challenging environments, e.g., in a vacuum, they can be modified with nitrogen. This work evaluates the tribological behavior and a possible compaction occurring during the initial tribological load in the rolling contact for pure and nitrogen-modified PVD–MoS2 coatings in a vacuum. Short-running tests (1000 cycles) of coated steel discs paired with uncoated steel discs made from 100Cr6 (1.3505, AISI 52100) were conducted on a two-disc tribometer. The slide-to-roll ratio of 10.5% was kept constant, while the load was varied in two steps from 1.1 GPa to 1.6 GPa. Subsequently, a comparison was made between the worn and the pristine coatings by means of nanoindentation and an optical analysis of the wear track. The formation of a load-bearing solid lubrication was achieved for both MoS2-variants. The main differences affected the material transfer and wear mechanisms. The worn coatings reached a similar wear coefficient of 4 × 10−6 mm3N−1m−1 and a possible compaction of the coatings was found, indicated through an increased indentation hardness (for MoS2 1158% and MoS2:N 96% at a 1.1 GPa load). The assumed tribological mechanism changed with nitrogen modification, but scales with increasing load. The nitrogen-modified MoS2 coating showed less compaction than pure MoS2, while the frictional behavior was improved by a 17% reduction of the coefficient of friction.

Anisotropic microstructure, nanomechanical and corrosion behavior of direct energy deposited Ti–13Nb–13Zr biomedical alloy

The present study investigates the anisotropic microstructure, nanomechanical and corrosion behavior of Ti–13Nb–13Zr biomedical alloys, which were fabricated using the direct energy deposition (DED) method. The microstructure of the as-deposited material was studied using a field-emission scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). We found anisotropic mechanical behavior using nanoindentation from strain rate sensitivity and creep tests. For the maximum load of 50 mN, the x-y plane (normal to the building direction) shows better indentation hardness and lower strain rate sensitivity value (0.014) compared to the x-z plane (0.022) (parallel to the building direction). The difference in the indentation hardness was mainly attributed to the smaller equiaxed prior-β grains and finer α’ martensitic laths on the x-y plane. In terms of creep behavior, the x-y planes show better creep strength than the x-z plane. Meanwhile, both planes show a very high creep exponent, which signifies a similar creep mechanism, i.e., dislocation based. Moreover, we further found the anisotropic corrosion behavior using electrochemical tests. Corrosion results reveal that the x-y plane is more corrosion-resistant than the x-z plane. In summary, the x-y plane of the direct energy deposited Ti–13Nb–13Zr alloy possesses better strength and corrosion resistance due to its finer microstructure.

Oxidation and wear behavior of CrAlMoN with varied Mo-content for cutting Ti6Al4V

The cutting of difficult to machine materials such as titanium alloys is challenging for the machining industry. In case of the titanium alloy Ti6Al4V, the properties of the material cause high temperatures, mechanical loads as well as high frequency vibrations at the cutting edge, leading to premature tool failure. The use of uncoated carbide tools is very common for machining of Ti based alloys. However, temperature active, self-lubricating physical vapor deposition (PVD) coatings like CrAlMoN showed promising results to reduce friction and wear during turning of Ti6Al4V. In the present study, self-lubricating (Cr34Al41Mo25)N, (Cr29Al36Mo35)N and (Cr25Al31Mo44)N coatings were investigated on cemented carbide tools. These were deposited by a hybrid process combining direct current Magnetron Sputtering and High Power Pulsed Magnetron Sputtering. Coating morphology, thickness, chemical composition, indentation hardness and modulus at ϑ = 20 °C, ϑ = 200 °C, ϑ = 400 °C and ϑ = 600 °C as well as the oxidation behavior were analyzed. Moreover, wear development after cutting tests using a CNC-lathe was investigated. Independent of Mo-content, all coating variants possessed a dense morphology and a smooth surface topography, as well as a coating adhesion class of HF1 to the cemented carbide substrate in Rockwell indentation tests according to DIN 4856. With an increasing amount of Mo, heat treatment temperature and time, more self-lubricating molybdenum oxides such as MoO3 and Mo4O11 were detected by Raman spectroscopy. Therefore, the coating with the highest amount of Mo possessed the highest amount of molybdenum oxides. After cutting tests, molybdenum oxides were also found on the tool flank face by Raman spectroscopy. The level of flank wear land width decreased with increasing amount of Mo.

Local control of microstructure and mechanical properties of high-strength steel in electric arc-based additive manufacturing

Additive manufacturing offers a significant potential for producing metallic parts with distinctly localised microstructures and mechanical properties, commonly known as functional grading. While functional grading is generally accomplished through compositional variations or in-situ thermo-mechanical treatments, variation of process parameters during additive manufacturing can offer a promising alternative approach. Focusing on the electric arc-based additive manufacturing process, this work focuses on the functional grading of high-strength steel (S690 grade) by adjusting the travel speed and inter-pass temperature. Through a combination of thermal simulations and experimental measurements on single bead-on-plate depositions, it is shown that the microstructure and the mechanical properties of parts can be controlled through the rational adjustment of process parameters. A rectangular block was fabricated to demonstrate functional grading using a constant wire feed rate and varying travel speed. The rectangular block consisted of a low heat input (LHI) region deposited between high heat input (HHI) zones. A graded microstructure was obtained with the HHI zones composed of a mixture of polygonal ferrite, acicular ferrite, and bainite, while the LHI region was primarily composed of martensite. The hardness and profilometry-based indentation plastometry measurements indicated that the LHI region exhibited higher hardness (32%) and strength (50%), but lower uniform elongation (80%), compared to the HHI zones. The present study demonstrates the potential to achieve functional grading by adjusting process parameters in electric arc-based additive manufacturing, providing opportunities for tailor-made properties in parts.

On determination of elastic modulus and indentation hardness by instrumented spherical indentation: influence of surface roughness and correction method

Although, surface roughness can influence the determination of elastic moduli and indentation hardness to some extent by instrumented spherical indentation test, limited work has been done to quantitatively reveal and minimize these influences. In the present work, through a large number of finite element (FE) simulations and analyses, we clarified the evolution trend of determined elastic moduli and indentation hardness corresponding to different normalized indentation depths (h/R) and normalized roughness (S q/R). On this basis, an area correction method was proposed to improve the measurement accuracy in the elastic moduli and indentation hardness. The FE results show that, with the newly proposed correction method, the maximum relative error in determined elastic moduli is reduced from about ±7% to ±2%, and that in the determined indentation hardness is reduced from about ±13% to ±5%, when S q/R ≤ 2.2 × 10−3 and h/R = 5%. Applications were then illustrated on four typical metallic materials (i.e., AA 7075, AA 2014, steel 316 L, and copper T2). The experimental results demonstrate that the proposed correction method is able to mitigate the effects of surface roughness on the determination of elastic moduli and indentation hardness to obtain more correct results.

Failure investigation of brazed copper winding bar strands of 250 MW stator

The present failure analysis investigates the failure of copper connectors and bus-bar windings of a 250 MW generator unit, of a steam powered turbine, which failed during service. An exhaustive microstructural and nanomechanical characterization was conducted in-order to determine the failure of copper bus-bar. Microstructure analysis revealed porosities in the brazed region with formation of numerous microconstituent phases. Furthermore, microstructure analysis revealed a network of numerous intergranular porosities on the failed copper side. SEM-EDS analysis of different microconstituents revealed a presence of Ag-rich dendritic phase, Cu-rich phase and lamellar eutectic microconstituents, highlighting a diverse microstructure. Nanoindentation measurements of different microconstituents and phases revealed a stark difference in the indentation hardness, thereby highlighting a strong mismatch between the observed microconstituents and phases.

Microphysical Modeling of Fault Slip and Stability Transition in Hydrothermal Conditions

AbstractField and laboratory observations indicate that the frictional behaviors of faults depend on hydrothermal conditions. We extend the microphysical Chen‐Niemeijer‐Spiers (CNS) model to hydrothermal conditions by using the observed temperature variation of indentation hardness to infer the temperature dependence of a microphysical parameter . This parameter is assumed constant in previous versions of the CNS model. A simple spring‐slider system is used to simulate the fault system and investigate the steady‐state frictional behaviors of wet granite gouges. Our numerical results quantitatively reproduce experimental data showing the frictional‐plastic transition. The results also describe the transition from velocity‐strengthening at low temperatures (<160°C), to velocity‐weakening at intermediate temperatures (160°C–370°C), then back to velocity‐strengthening at high temperatures (>370°C). In our extended CNS model, these results suggest that the dominant shear deformation mechanism does transition from frictional granular flow to fully plastic creep with increasing temperature.

Development of a mandrel indentation test to evaluate surface hardness of dimensional building stones and comparison to Vickers hardness

The present research introduces a new method namely mandrel indentation test (MIT) to evaluate surface hardness of rocks and building stones and comparing its results with the Vickers hardness test results. For performing the test, first, its apparatus was designed and built from hard and rigid steel in a turning workshop. Then, it was used on 50 common carbonate building stones including 30 limestones and 20 travertines in the laboratory. Also, surface hardness of the stones was evaluated by the Vickers hardness test. The values of mandrel indentation hardness (MIH) for the building stones were obtained between 31.75 and 113.85 kgf/mm2, and the values of Vickers hardness (HV) were obtained between 286.11 and 1361.98 kgf/mm2. The developed correlation analysis results together with the obtained Pearson, Spearman, and Kendall correlation coefficients indicated that the values of the surface hardness resulted from this approach is strongly correlated to the values of the Vickers test by a direct linear relation. The stablished simple regression analysis has confirmed the results of the correlation analysis by a determination coefficient of 0.841. Five well‐known statistical indexes were used to assess accuracy performance degree of the developed regression model. As an important finding of the research, the introduced approach has high potential and accuracy for evaluating surface hardness of the studied building stones. Finally, a classification system was proposed to classify different building stones based on their surface hardness. Based on the classification, the studied building stones are classified as very soft to moderately hard with low hardness ratio.

Atomic simulation of the effect of supersonic fine particle bombardment process parameters on the mechanical properties of polycrystalline γ-TiAl alloy

γ-TiAl alloys are the most promising lightweight high-temperature structural materials, but the materials often fail from the surface, which is mainly attributed to the stress state of the material surface. In this paper, the orthogonal experiment method and molecular dynamics modeling are used to choose a set of the best process parameters for supersonic fine particle bombardment (SFPB). Furthermore, by determining the optimal process parameters, this study examines the influence of residual stress distribution on the mechanical properties of the material under various process conditions. The simulation results reveal that the residual stress distribution is minimally impacted by particle radius, nonetheless, maintaining a moderate level of compressive residual stress within a specific range can substantially augment both the tensile strength and indentation hardness. An increase in the number of particles results in a more uniform distribution of surface residual stresses. Conversely, an increase in the number of impacts causes stress concentration to intensify at the particle’s contact point, and thus a deeper distribution of residual stress is observed. This study illustrates how the mechanical properties of polycrystalline γ-TiAl alloy are affected by the process parameters of SFPB in terms of atomic size in order to develop and select the optimal SFPB parameters.

Assessment of the Pitting, Crevice Corrosion, and Mechanical Properties of Low-Temperature Plasma-Nitrided Inconel Alloy 718

A comparative study on the mechanical properties, scratch resistance, and localized corrosion (pitting and crevice) of plasma-nitrided Inconel alloy 718 (UNS NO7718: IN 718) was carried out. Thermochemical treatment was performed at low temperatures (400 and 450 °C) for 4 h. The treatment formed layers with thicknesses of 7.17 ± 0.89 µm (400 °C) and 7.96 ± 0.48 µm (450 °C). The XRD and nanohardness analyses indicated the formation of a hard layer composed of the expanded austenite phase (γN), CrN at 400 °C, and CrN + γ at 450 °C, with a maximum indentation hardness of 12 and 12.5 GPa, respectively, when compared to the 5 GPa substrate hardness. The scratching tests (2–8 N) showed that with increasing load, the nitrided surfaces had a transition from 100% microcutting to a combination of microplowing/cutting, with the presence of cracks. The critical load of the nitrided surfaces was 3 N for 400 °C and 4 N for 450 °C. The untreated condition maintained a crack-free combined mechanism regardless of the load. For the same load, the nitrided surfaces held lower coefficient of friction values and higher scratch resistance values, which were more pronounced at 450 °C. The linear polarization tests (3.56 wt.% NaCl) showed pitting corrosion in all samples, with the 450 °C condition being less resistant. Nitriding at 400 °C increased the crevice corrosion resistance of Inconel, while at 450 °C, it severely damaged it. Nitriding at 400 °C brought concomitant gains in hardness and scratch and crevice corrosion resistance when compared to the as-received IN 718.

Simulated nanoindentation into single-phase fcc Fe_{x}Ni_{1-x} alloys predicts maximum hardness for equiatomic stoichiometry

We investigate by molecular dynamics simulation the mechanical behavior of concentrated alloys under nanoindentation for the special example of single-phase fcc Fe_{x}Ni_{1-x} alloys. The indentation hardness is maximum for the equiatomic alloy, x=0.5. This finding is in agreement with experimental results on the strength of these alloys under uniaxial strain. We explain this finding with the increase of the unstable stacking fault energy in the alloys towards x=0.5. With increasing Fe content, loop emission from the plastic zone under the indenter becomes less pronounced and the plastic zone features a larger fraction of screw dislocation segments; simultaneously, the length of the dislocation network and the number of atoms in the stacking faults generated in the plastic zone increase. However, the volume of twinned regions in the plastic zone is highest for the elemental solids and decreases for the alloys. This feature is explained by the fact that twinning proceeds by the glide of dislocations on adjacent parallel lattice planes; this concerted motion is less efficient in the alloys. Finally, we find that surface imprints show increasing pile-up heights with increasing Fe content. The present results will be of interest for hardness engineering or generating hardness profiles in concentrated alloys.

Micromechanical characterization of a reduced-activation ferritic/martensitic steel by instrumented indentation and scratch methods

Micromechanical properties of a reduced-activation ferritic/martensitic steel CLF-1 were characterized by nanoindentation tests with Berkovich indenter, microhardness tests with Vickers and Knoop indenters, and microscratch tests with Berkovich and spherical indenters to investigate the effects of different indenters. Elastic modulus and indentation hardness obtained by various methodologies such as energy-based and displacement-based approaches are consistent with those obtained by Oliver & Pharr method. The reasonable fracture toughness of CLF-1 steel can also be obtained by energy-based nanoindentation method based on the deterioration of indentation hardness with the critical void volume fraction of 0.49.

Effect of Cu and Cr addition on the structure, anticorrosion and nanomechanical properties of new Al-Ni-Fe-(Cr,Cu) alloys

This work used a thermodynamic approach to design and investigate new complex compositional Al-Ni-Fe-(Cr,Cu) alloys based on aluminum. This work tends to understand the change in microstructure during the rapid solidification process and to evaluate the anticorrosion and nanomechanical properties of the developed alloys. Optimizing thermodynamic parameters such as configurational entropy and Gibbs free energy was used to predict the chemical composition of the studied alloys. The samples were cooled in two ways. The ingots were slowly cooled, while the plates were cast using fast cooling by the high-pressure die-casting method. The presence of a quasicrystalline decagonal phase D-Al71Ni24Fe5 was identified together with crystalline Al3Ni, Al3Ni2, and Al9Ni1.3Fe0.7 phases for the rapidly solidified Al72Ni24Fe4 alloy. The best electrochemical parameters were observed for the Al72Ni24Fe2.5Cr1.5 alloy. The local galvanic microcells were formed in the studied alloys due to large potential differences (>50 mV) between the Al-Ni and Al-Ni-Fe phases. The highest average indentation hardness values were observed for Al72Ni24Fe4 (9.98 ± 1.75 GPa) after normal and rapid solidification. The higher ductility of the Al72Ni24Cr1.5Fe2.5 alloy compared to Al72Ni24Fe4 and Al72Ni24Cu1.5Fe2.5 could be confirmed by the lowest average hardness and Young's modulus values.

Crack reduction in Inconel 939 with Si addition processed by laser powder bed fusion additive manufacturing

Inconel 939 (IN939) suffers from cracking in the laser powder bed fusion based additive manufacturing (LPBF-AM) process. Previous studies attempted to minimize the crack density by reducing the Si content. In contrast, this paper demonstrates that Si addition can substantially lower the crack density in LPBF-AM IN939 alloy parts. Si addition into IN939 shows a moderate impact on the crystallographic orientation and grain size of LPBF-AM parts, and promotes the formation of precipitates. Mechanical tests show that Si addition increases tensile strength and indentation hardness but decreases ductility. This work suggests that the dominant cracking mode in LPBF-AM IN939 alloy parts is solidification cracking, the suppression of which by Si addition can be qualitatively rationalized using Clyne’s model and Kou’s model. The present findings provide a different perspective on designing defect-free LPBF-AM Ni-based superalloy parts with balanced mechanical properties, one which can be extended to other alloy systems.

Elastic-plastic properties of Li2B4O7 determined by nanoindentation

Relevance. Crystalline and amorphous lithium tetraborate (Li2B4O7) has a wide range of practical applications due to its physical properties. The knowledge of the mechanical characteristics of the surface layers of these materials, which are studied by nanoindentation, is necessary for optimising the technological processes for obtaining “optically perfect” samples. Aim. A comparative study of the mechanical properties and deformation mechanisms of glassy and crystalline Li2B4O7 samples in a wide range of applied loads. Methodology. The elastic-plastic properties of crystalline and glassy lithium tetraborate were investigated using the multiple-loading cyclic nanoindentation method. The samples were measured at maximum loading forces of 50, 100, 150, 200, 250, 300, 350, 400, 450, and 500 mN. Four measurements (in the form of a 2x2 matrix) were made at a distance of 50 µm from each other on each sample and at each load. Young’s modulus, hardness, and Poisson’s ratio of Li2B4O7 glass were also calculated using the Makishima-Mackenzie theory. Results. The load-displacement curves and graphs of the dependence of the average contact pressure on the displacement of the diamond Berkovich indenter were obtained, which have a “smooth” shape and no anomalies associated with “pop-in” or “pop-out” effects. The indentation modulus (Young’s modulus E) and hardness H of the studied samples were obtained from the experimental P-h load-displacement diagrams. The measured values mainly depend on the applied load or the contact depth of the indenter penetration into the crystalline and vitreous lithium tetraborate. Conclusions. Both the hardness and Young’s modulus of Li2B4O7 glass are lower than those of the single crystal, indicating a lower resistance of amorphous lithium tetraborate to elastic and plastic deformations. The obtained experimental values of hardness and Young’s modulus of Li2B4O7 glass correlate well with the results of the calculation within the framework of the Makishima-Mackenzie theory. Multiple-loading cyclic nanoindentation leads to deformation densification of glassy Li2B4O7 due to changes in the angles and lengths of chemical bonds, which leads to a decrease in the free volume in the medium-order structure of glass, as well as a change in the coordination of Boron atoms relative to Oxygen, i.e., the transformation of three-coordinated Boron into four-coordinated Boron

Synergistic contribution of bio-based additives in wood paint: The combined effect of pigment deriving from spirulina and multifunctional filler based on carnauba wax

This work aims to reveal the synergistic behavior of two bio-based additives on the durability and protective behavior of a bio-based wood paint. The powder extract form spirulina was introduced as a natural pigment, while carnauba wax was used as a multifunctional filler. The impact of the two additives on the morphology of the coatings was investigated by scanning electron microscopy observations, while their role on the durability of the paint was assessed by exposing the samples to UV-B radiation and continuous thermal shocks. Infrared spectroscopy analysis, colorimetric inspections, adhesion test and scanning electron microscope observations were employed to investigate the impact of the synergic behavior of the bio-based additives. Furthermore, the role of the spirulina and wax powders on the barrier performance of the coatings was evaluated by liquid resistance test ad water uptake test. Finally, Buchholz hardness indentation test and the scrub test were employed to estimate the effect of the additives on the mechanical properties of hardness and abrasion resistance of the coatings. Ultimately, this work demonstrates the interesting synergy of spirulina and wax, able to provide an intense coloring and certain aesthetic features to the paint, to improve the water-repellent properties of the surface and to increase the abrasion resistance of the composite layer.