scholarly journals Fatigue Behavior of the Rare Earth Rich EV31A Mg Alloy: Influence of Plasma Electrolytic Oxidation

2017 ◽  
Author(s):  
Lorella Ceschini ◽  
Alessandro Morri ◽  
Valerio Angelini ◽  
Simone Messieri
Keyword(s):  
Surface Roughness ◽  
Rare Earth ◽  
Fatigue Strength ◽  
Plasma Electrolytic Oxidation ◽  
Crack Nucleation ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Mg Alloy ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic

Rare earth rich magnesium alloys are used in aerospace and automotive fields because of their high specific strength and good castability. However, due to their low corrosion resistance, protective surface treatments, such as conversion coating or electroless plating are necessary, when they have to be used in humid or corrosive environments. The present study was aimed to evaluate the effect of Plasma Electrolytic Oxidation (PEO) and different surface roughness  (Ra≈0.8 μm and Ra≈0.3 μm) on the rotating bending fatigue of an innovative Mg alloy, with a high content of Nd (up to 3.1 wt%) and Gd (up to 1.7 wt %). Fatigue tests revealed a 15% decrease in the fatigue strength of the PEO treated alloy (fatigue strength = 88 MPa) with respect to the bare alloy (fatigue strength = 103 MPa). The reduction of fatigue strength was mainly due to the residual tensile stresses induced by the PEO treatment. The effect of surface roughness on the bare alloy was, instead, negligible. The mechanisms of crack initiation were similar in the untreated and PEO treated alloy, with crack nucleation sites located in correspondence of large facets of the cleavage planes.

scholarly journals Fatigue Behavior of the Rare Earth Rich EV31A Mg Alloy: Influence of Plasma Electrolytic Oxidation

2017 ◽  
Author(s):  
Lorella Ceschini ◽  
Alessandro Morri ◽  
Valerio Angelini ◽  
Simone Messieri
Keyword(s):  
Surface Roughness ◽  
Rare Earth ◽  
Plasma Electrolytic Oxidation ◽  
Crack Nucleation ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Mg Alloy ◽  
Specific Strength ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic

Rare earth rich magnesium alloys are used in aerospace and automotive fields because of their high specific strength and good castability. However, due to their low corrosion resistance, protective surface treatments, such as conversion coating or electroless plating are necessary, when they have to be used in humid or corrosive environments. The present study was aimed to evaluate the effect of Plasma Electrolytic Oxidation (PEO) and different surface roughness on the rotating bending fatigue of an innovative Mg alloy, with a high content of Nd (up to 3.1 wt%) and Gd (up to 1.7 wt %). Fatigue tests revealed a 15% decrease in the fatigue strength of the PEO treated alloy with respect to the bare alloy, probably due to the residual tensile stresses induced by the treatment. The effect of surface roughness on the bare alloy was, instead, negligible. The mechanisms of crack initiation were similar in the untreated and PEO treated alloy, with crack nucleation sites located in correspondence of large facets of the cleavage planes.

scholarly journals Fatigue Behavior of the Rare Earth Rich EV31A Mg Alloy: Influence of Plasma Electrolytic Oxidation

Metals ◽  
2017 ◽  
Vol 7 (6) ◽  
pp. 212 ◽  
Author(s):  
Lorella Ceschini ◽  
Alessandro Morri ◽  
Valerio Angelini ◽  
Simone Messieri
Keyword(s):  
Rare Earth ◽  
Plasma Electrolytic Oxidation ◽  
Fatigue Behavior ◽  
Mg Alloy ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
The Rare Earth

scholarly journals Bioactivity Performance of Pure Mg after Plasma Electrolytic Oxidation in Silicate-Based Solutions

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 2094
Author(s):  
Yevheniia Husak ◽  
Joanna Michalska ◽  
Oleksandr Oleshko ◽  
Viktoriia Korniienko ◽  
Karlis Grundsteins ◽  
...  
Keyword(s):  
Cell Culture ◽  
Oxide Layer ◽  
Plasma Electrolytic Oxidation ◽  
Oxide Coating ◽  
Mg Alloy ◽  
Aureus Strain ◽  
Active Surface Area ◽  
Corrosion Properties ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic

The biodegradable metals, including magnesium (Mg), are a convenient alternative to permanent metals but fast uncontrolled corrosion limited wide clinical application. Formation of a barrier coating on Mg alloys could be a successful strategy for the production of a stable external layer that prevents fast corrosion. Our research was aimed to develop an Mg stable oxide coating using plasma electrolytic oxidation (PEO) in silicate-based solutions. 99.9% pure Mg alloy was anodized in electrolytes contained mixtures of sodium silicate and sodium fluoride, calcium hydroxide and sodium hydroxide. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), contact angle (CA), Photoluminescence analysis and immersion tests were performed to assess structural and long-term corrosion properties of the new coating. Biocompatibility and antibacterial potential of the new coating were evaluated using U2OS cell culture and the gram-positive Staphylococcus aureus (S. aureus, strain B 918). PEO provided the formation of a porous oxide layer with relatively high roughness. It was shown that Ca(OH)2 was a crucial compound for oxidation and surface modification of Mg implants, treated with the PEO method. The addition of Ca2+ ions resulted in more intense oxidation of the Mg surface and growth of the oxide layer with a higher active surface area. Cell culture experiments demonstrated appropriate cell adhesion to all investigated coatings with a significantly better proliferation rate for the samples treated in Ca(OH)2-containing electrolyte. In contrast, NaOH-based electrolyte provided more relevant antibacterial effects but did not support cell proliferation. In conclusion, it should be noted that PEO of Mg alloy in silicate baths containing Ca(OH)2 provided the formation of stable biocompatible oxide coatings that could be used in the development of commercial degradable implants.

Sign in / Sign up

Export Citation Format

Share Document