Diego Emilio Lozano De La Garza | Universidad de Monterrey (original) (raw)

Papers by Diego Emilio Lozano De La Garza

Cobalt-based alloys are widely used in the manufacture of joint prostheses. In this study, the ef... more Cobalt-based alloys are widely used in the manufacture of joint prostheses. In this study, the effect of boron additions and heat treatment on the ASTM F75 was evaluated by rotating bending fatigue. The boron ranged from 0.06-1 wt %. The alloys were tested in as-cast and heattreated conditions. In the as-cast condition, the infinite life was observed at 380 MPa, improving to 433-615 MPa according to the amount of boron added. In the heat treatment condition, the fatigue resistance was improved only in the base alloy. The addition of 0.06 wt % boron and heat treatment led to the same resistance as in the as-cast condition. Adding large amounts of boron combined with heat treatment diminished the fatigue limit. The fracture analysis revealed primarily brittle behaviour with some ductile features even on the same sample; only the heat-treated alloy with 0.06 wt % boron was clearly ductile. This alloy also exhibited notably better toughness to crack propagation.

Cobalt-based alloys are extensively used in orthopedic applications for joint replacements due to... more Cobalt-based alloys are extensively used in orthopedic applications for joint replacements due to their wear and corrosion resistance. Corrosion, however, is often associated with fatigue failure in these orthopedic devices. In this study, the effect of boron addition on the corrosion behavior of CoCrMo alloys was studied using linear polarization resistance, potentiodynamic polarization curves, electrochemical impedance spectroscopy, and cyclic voltammetry. The samples were analyzed under as-cast and heat treatment conditions after 21 days of immersion in phosphate-buffered saline (PBS) solution at 37 • C. The boron addition increased the particle content, while the heat treatment promoted enlargement and even distribution of the precipitates throughout the structure. The corrosion resistance was improved by both boron and heat treatments. The best performance was observed for a heat-treated alloy having a very small amount of boron, which had an increased resistance to corrosive attack. Such behavior was attributed to the homogenized microstructure achieved by boron and heat treatment that helped to form a stable passive layer of chromium oxide which endured the 21 days of immersion.

The AISI 4130 steel grade is commonly used in piping systems, where optimum chemical composition ... more The AISI 4130 steel grade is commonly used in piping systems, where optimum chemical composition and heat treatment can exhibit high yield strength, good ductility, and moderate weldability depending on composition. However, this steel grade is characterized by its low hardenability, which limits a good transformation during quenching in heavy sections. In order to improve hardenability, Ni was added and C was reduced for the same level of CE (0.7).

A method for estimating the crack growth rate in steel during rotating-bending fatigue testing is... more A method for estimating the crack growth rate in steel during rotating-bending fatigue testing is presented. Constant deflection tests were conducted in which the initial load remained constant prior to crack nucleation, when it decreased as the crack grew. In the proposed approach, steel samples were sharp-notched to produce a characteristic circular fracture upon loading and the final fracture area was correlated with a ratio of the load prior to fracture and the initial load. In this method, the deflection imposed is a function of a material's elastic modulus rather than its yield strength and the correlation obtained to estimate the average crack length as a function of the instantaneous load is independent of the applied stress or steel grade.

Cobalt-based alloys are widely used in the manufacture of joint prostheses. In this study, the ef... more Cobalt-based alloys are widely used in the manufacture of joint prostheses. In this study, the effect of boron additions and heat treatment on the ASTM F75 was evaluated by rotating bending fatigue. The boron ranged from 0.06-1 wt %. The alloys were tested in as-cast and heattreated conditions. In the as-cast condition, the infinite life was observed at 380 MPa, improving to 433-615 MPa according to the amount of boron added. In the heat treatment condition, the fatigue resistance was improved only in the base alloy. The addition of 0.06 wt % boron and heat treatment led to the same resistance as in the as-cast condition. Adding large amounts of boron combined with heat treatment diminished the fatigue limit. The fracture analysis revealed primarily brittle behaviour with some ductile features even on the same sample; only the heat-treated alloy with 0.06 wt % boron was clearly ductile. This alloy also exhibited notably better toughness to crack propagation.

Cobalt-based alloys are extensively used in orthopedic applications for joint replacements due to... more Cobalt-based alloys are extensively used in orthopedic applications for joint replacements due to their wear and corrosion resistance. Corrosion, however, is often associated with fatigue failure in these orthopedic devices. In this study, the effect of boron addition on the corrosion behavior of CoCrMo alloys was studied using linear polarization resistance, potentiodynamic polarization curves, electrochemical impedance spectroscopy, and cyclic voltammetry. The samples were analyzed under as-cast and heat treatment conditions after 21 days of immersion in phosphate-buffered saline (PBS) solution at 37 • C. The boron addition increased the particle content, while the heat treatment promoted enlargement and even distribution of the precipitates throughout the structure. The corrosion resistance was improved by both boron and heat treatments. The best performance was observed for a heat-treated alloy having a very small amount of boron, which had an increased resistance to corrosive attack. Such behavior was attributed to the homogenized microstructure achieved by boron and heat treatment that helped to form a stable passive layer of chromium oxide which endured the 21 days of immersion.

The AISI 4130 steel grade is commonly used in piping systems, where optimum chemical composition ... more The AISI 4130 steel grade is commonly used in piping systems, where optimum chemical composition and heat treatment can exhibit high yield strength, good ductility, and moderate weldability depending on composition. However, this steel grade is characterized by its low hardenability, which limits a good transformation during quenching in heavy sections. In order to improve hardenability, Ni was added and C was reduced for the same level of CE (0.7).

A method for estimating the crack growth rate in steel during rotating-bending fatigue testing is... more A method for estimating the crack growth rate in steel during rotating-bending fatigue testing is presented. Constant deflection tests were conducted in which the initial load remained constant prior to crack nucleation, when it decreased as the crack grew. In the proposed approach, steel samples were sharp-notched to produce a characteristic circular fracture upon loading and the final fracture area was correlated with a ratio of the load prior to fracture and the initial load. In this method, the deflection imposed is a function of a material's elastic modulus rather than its yield strength and the correlation obtained to estimate the average crack length as a function of the instantaneous load is independent of the applied stress or steel grade.