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Characterization of thermally oxidized titanium based coating

Cetiner D., Paksoy A. H., Tazegul O., Atar E., Cimenoglu H.

Journal of Achievements in Materials and Manufacturing Engineering

2016

Vol. 75, nr 2

49--54

Purpose: Aim of the study is to improve the bioactivity of CoCr alloy upon covering the surface with titanium based coating. Design/methodology/approach: CoCr alloy was coated by cold spraying of powder mixture having a composition of 92 wt.%Ti + 8 wt.%Al. Coated samples were thermally oxidized at 600°C for 60 hours. Characterization of the coating was made by X-Ray diffraction analyses, microstructural surveys, cross-section and surface SEM elemental mapping analyses, roughness and hardness measurements. Findings: Results showed that sequential application of cold spray and thermal oxidation processes provided the multi-layered coating consisting of an inner titanium based layer and an outer oxide layer consisted of TiO2 and Al2O3. Thermal oxidation also caused the remarkable increasing in the surface hardness as compared to the as-cold sprayed state. Practical implications: Modifying the surface of CoCr metallic implants for long term success. Originality/value: Producing a multilayer coating on the surface of the CoCr alloy for biomedical application by sequential application of cold spray and thermal oxidation processes is the orginality of the study.

The effect of nickel on sliding wear behaviour of cobalt-based hardfacing alloy at elevated temperature

Motallebzadeh A., Atar E., Cimenoglu H.

Archives of Materials Science and Engineering

2014

Vol. 69, nr 2

81--87

Purpose: To investigate the effect of addition of nickel on the microstructure, hardness and tribological properties of cobalt-based hardfacing alloy (Stellite 12) deposited by plasma transferred arc (PTA) welding technique. Design/methodology/approach: Microstructural characterization was carried out on deposited layers by utilising X-ray diffractometer and energy dispersive X-ray (EDX) equipped scanning electron microscope (SEM). Mechanical properties of the coatings were determined by hardness measurements and sliding wear tests. Hardness of the deposited layers was evaluated in HV scale. Wear tests were conducted under normal load of 3 N at room temperature (RT), 300 and 500ºC. Findings: Microstructural studies revealed that addition of nickel into Stellite 12 alloy dominated FCC crystal structure in the cobalt rich solid solution matrix rather than HCP crystal structure. Furthermore, nickel addition reduced the hardness and wear resistance of the deposited layer at room temperature. Nickel containing Stellite12 deposited layers demonstrated better wear resistance as compared to a Stellite12 deposited layer at high temperatures (300 and 500°C) owing to the formation of stable oxide layer on the worn surface. Practical implications: Determining the sliding wear performance of Stellite 12 alloy deposited layer which nickel is added to enhance the corrosion resistance in harsh environments. Originality/value: The investigation of high temperature wear performance of Stellite 12 alloy deposited layer upon addition of nickel.