TY - JOUR
T1 - Apparent fracture toughness of the CoB-CO2B interface
AU - Campos-Silva, I.
AU - Hernández-Ramírez, E. J.
AU - Mondragón-Nava, H. I.
AU - Contreras-Hernández, A.
AU - Fernández-Valdés, D.
AU - Meneses-Amador, A.
AU - Delgado-Brito, A. M.
N1 - Publisher Copyright:
© 2020 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959
PY - 2020/5/14
Y1 - 2020/5/14
N2 - In this study, new results for the interfacial fracture toughness of the CoB-Co2B layer formed at the surface of the ASTM F1537, Standard Specification for Wrought Cobalt-28Chromium6Molybdenum Alloys for Surgical Implants (UNS R31537, UNS R31538, and UNS R31539), alloy were estimated. Initially, the cobalt boride layers were developed by means of the powder-pack boriding process at 1,173 K with 6 h of exposure, and 1,223 K with 8 h of exposure. The depth-sensing Vickers microindentation tests were performed using applied loads ranging between 1 and 2.3 N to generate a crack along the CoB-Co2B interface. The apparent fracture toughness ðKcaÞ of the CoB-Co2B interface was estimated using a half-penny cracking model and considering the interfacial values of the Young's modulus, hardness, and the critical point (Pc, ac), in which Pc was considered as a criterion of the adhesion between CoB and Co2B. To verify the influence of the cobalt boride layer thickness and the magnitude of the residual stresses developed on CoB-Co2B interface, the cracking model was extended to estimate the Kca for the boriding condition at 1,273 K with 6 h of exposure. In addition, the magnitude of the shear stresses on the CoB-Co2B interface was analyzed by the finite element method as a function of the indentation loads of 1 and 2.3 N using the boriding conditions of 1,173 K with 6 h of exposure and 1,223 K with 8 h of exposure. The results showed that the interfacial fracture toughness of the CoB-Co2B increased as a function of the CoB layer thickness, whereas the magnitude of the compressive residual stresses decreased for the thicker cobalt boride layer formed at 1,273 K with 6 h of exposure. Finally, the distribution of the maximum shear stresses located on the CoB-Co2B interface oscillated from 3.9 to 4.4 GPa according to the indentation loads.
AB - In this study, new results for the interfacial fracture toughness of the CoB-Co2B layer formed at the surface of the ASTM F1537, Standard Specification for Wrought Cobalt-28Chromium6Molybdenum Alloys for Surgical Implants (UNS R31537, UNS R31538, and UNS R31539), alloy were estimated. Initially, the cobalt boride layers were developed by means of the powder-pack boriding process at 1,173 K with 6 h of exposure, and 1,223 K with 8 h of exposure. The depth-sensing Vickers microindentation tests were performed using applied loads ranging between 1 and 2.3 N to generate a crack along the CoB-Co2B interface. The apparent fracture toughness ðKcaÞ of the CoB-Co2B interface was estimated using a half-penny cracking model and considering the interfacial values of the Young's modulus, hardness, and the critical point (Pc, ac), in which Pc was considered as a criterion of the adhesion between CoB and Co2B. To verify the influence of the cobalt boride layer thickness and the magnitude of the residual stresses developed on CoB-Co2B interface, the cracking model was extended to estimate the Kca for the boriding condition at 1,273 K with 6 h of exposure. In addition, the magnitude of the shear stresses on the CoB-Co2B interface was analyzed by the finite element method as a function of the indentation loads of 1 and 2.3 N using the boriding conditions of 1,173 K with 6 h of exposure and 1,223 K with 8 h of exposure. The results showed that the interfacial fracture toughness of the CoB-Co2B increased as a function of the CoB layer thickness, whereas the magnitude of the compressive residual stresses decreased for the thicker cobalt boride layer formed at 1,273 K with 6 h of exposure. Finally, the distribution of the maximum shear stresses located on the CoB-Co2B interface oscillated from 3.9 to 4.4 GPa according to the indentation loads.
KW - Cobalt boride layer
KW - Cracking model
KW - Finite element method
KW - Interfacial fracture toughness
KW - Powder-pack boriding
KW - Shear stresses
UR - http://www.scopus.com/inward/record.url?scp=85084790407&partnerID=8YFLogxK
U2 - 10.1520/MPC20190074
DO - 10.1520/MPC20190074
M3 - Artículo
AN - SCOPUS:85084790407
SN - 2165-3992
VL - 9
JO - Materials Performance and Characterization
JF - Materials Performance and Characterization
IS - 3
M1 - MPC20190074
ER -