2014 KEM Stainless steels biomedical.doc

Revista Brasileira De Engenharia Biomedica, 2014

The mechanical properties and corrosion resistance of a material are dependent on its microstructure and can be modifi ed by phase transformation. When a phase transformation occurs in a material it usually forms at least one new phase, with physical-chemical characteristics that differ from the original phase. Moreover, most phase transformations do not occur instantly. This paper presents an evaluation of the phase transformation of martensitic stainless steels ASTM 420A and ASTM 440C when submitted to different thermal processes. Methods: Dilatometry tests were performed with several continuous heating and cooling rates in order to obtain the profi les of the continuous heating transformation (CHT) and continuous cooling transformation (CCT) diagrams for these two types of steel. Also, the temperature ranges for the formation of the different phases (ferrite and carbides; ferrite; austenite and carbides; non-homogeneous and homogeneous austenite phases) were identifi ed. Rockwell hardness (HRC) tests were performed on all thermally treated steels. Anodic and cathodic potential dynamic polarization measurements were carried out through immersion in enzymatic detergent as an electrolyte for different samples submitted to the thermal processes in order to select the best routes for the heat treatment and to recommend steels for the manufacture of surgical tools. Results: The martensitic transformation temperature tends to increase with increasing temperature for the initiation of cooling. The 440C steel had a higher hardness value than the 420A steel at the austenitizing temperature of 1100 °C. Above the austenitizing temperature of 1100 °C, the material does not form martensite at the cooling rate used, which explains the sharp decline in the hardness values. Conclusion: The study reported herein achieved its proposed objectives, successfully investigating the issues and indicating solutions to the industrial problems addressed, which are frequently encountered in the manufacture of surgical instruments.

Introduction: The mechanical properties and corrosion resistance of a material are dependent on its microstructure and can be modifi ed by phase transformation. When a phase transformation occurs in a material it usually forms at least one new phase, with physical-chemical characteristics that differ from the original phase. Moreover, most phase transformations do not occur instantly. This paper presents an evaluation of the phase transformation of martensitic stainless steels ASTM 420A and ASTM 440C when submitted to different thermal processes. Methods: Dilatometry tests were performed with several continuous heating and cooling rates in order to obtain the profi les of the continuous heating transformation (CHT) and continuous cooling transformation (CCT) diagrams for these two types of steel. Also, the temperature ranges for the formation of the different phases (ferrite and carbides; ferrite; austenite and carbides; non-homogeneous and homogeneous austenite phases) were identifi ed. Rockwell hardness (HRC) tests were performed on all thermally treated steels. Anodic and cathodic potential dynamic polarization measurements were carried out through immersion in enzymatic detergent as an electrolyte for different samples submitted to the thermal processes in order to select the best routes for the heat treatment and to recommend steels for the manufacture of surgical tools. Results: The martensitic transformation temperature tends to increase with increasing temperature for the initiation of cooling. The 440C steel had a higher hardness value than the 420A steel at the austenitizing temperature of 1100 °C. Above the austenitizing temperature of 1100 °C, the material does not form martensite at the cooling rate used, which explains the sharp decline in the hardness values. Conclusion: The study reported herein achieved its proposed objectives, successfully investigating the issues and indicating solutions to the industrial problems addressed, which are frequently encountered in the manufacture of surgical instruments.

Transstellar journal, 2018

Stainless steel is well known for its good corrosion resistance, which are cheaply available in the market. Martensitic stainless steels find rare applications because of their high hardness and wear resistance in tempered condition. In order to decrease their hardness and promote the ductility AISI431 Grade martensitic stainless steel samples were subjected to vacuum annealing and vacuum hardening/tempering.3 samples were chosen and were subjected to vacuum annealing and named as VA1, VA2, and VA3. 3 samples were subjected to vacuum tempering and named as VT1, VT2, and VT3. All the samples underwent with a pin on the disc testing to analyse the wear behaviour. All the samples are subjected to various metallographic test to get the results like optical microscope results, hardness tests, scanning electron microscope results and (EDAX) Energy Dispersive Spectroscopy. An untreated sample is used for the comparison with the treated samples. The microstructure comprises of tempered martensite with haphazardly dispersed carbides in the framework.

Microscopy and Microanalysis

IOP Publishing, 2021

This work examines the influence of heat treatment processes, using oil and water at various temperatures as quenching media, on the mechanical, corrosion, and microstructural properties of 316L austenitic stainless steel as used as a biomaterial for temporary and permanent bone repairs or grafts and as a plate bone fixation during periods of treatment. The results show that the highest microhardness rate is obtained using normal water as a cooling media; this sample reached 157.7 Hv., a 9.97% higher value than that obtained using oil media and an 18.66% higher value than that obtained using one-hour heating. The microstructure images for the quenched samples in oil displayed more evenly and uniformly distributed carbon particles, suggesting the formation of a more pearlite structure as compared with the water-quenched samples, however. The highest polarization resistance value was obtained when using water cooling media with two hours heating time; this reached 2.849 V/μA. Dec., while the minimum value, reached 0.185 V/μA. Dec., was obtained using the hot water cooling medium. The minimum corrosion rate value was obtained using the oil cooling media; this was 0.34 x10-5 milli-in./year, while the maximum value reached 0.86x10-5 milli-in./year for the water cooling medium with a three-hour heating duration. The resulting equivalent von-Mises stress reached its maximum value at 285.24 MPa at 150 Kg patient weight and 5 mm plate thickness. The total deformation reached a minimum value of 0.0723 mm, while the stress safety factor reached a maximum value of 2.7 for a patient weight of 60 Kg when using 10 mm plate thickness. The equivalent elastic strain and the strain energy reached minimum values of 4.7 x 10-4 mm and 0.021 mJ for a patient weight of 60 Kg when using 5 mm plate thickness, respectively.

Materials Science and Engineering: A, 2006

In this study, the mechanical properties of welded austenitic stainless steel plates type AISI 316L are carried out using stress strain microprobe in welded region, and heat affected zone. Automated metal inert gas welding process has been used. Different heat inputs are selected in order to describe the effect of metallurgical aspects on mechanical properties like ultimate tensile strength, yield strength, and hardness. The results showed that the heat input 305 J/mm provides maximum strength, and hardness value. This can be attributed to formation of delta ferrite phase and its shape, which subsequently changes the mechanical properties.

In this study, the mechanical properties of welded austenitic stainless steel plates type AISI 316L are carried out using stress strain microprobe in welded region, and heat affected zone. Automated metal inert gas welding process has been used. Different heat inputs are selected in order to describe the effect of metallurgical aspects on mechanical properties like ultimate tensile strength, yield strength, and hardness. The results showed that the heat input 305 J/mm provides maximum strength, and hardness value. This can be attributed to formation of delta ferrite phase and its shape, which subsequently changes the mechanical properties.

Applied Sciences, 2020

Wire arc additive manufacturing (WAAM) has been considered as a promising technology for the production of large metallic structures with high deposition rates and low cost. Stainless steels are widely applied due to good mechanical properties and excellent corrosion resistance. This paper reviews the current status of stainless steel WAAM, covering the microstructure, mechanical properties, and defects related to different stainless steels and process parameters. Residual stress and distortion of the WAAM manufactured components are discussed. Specific WAAM techniques, material compositions, process parameters, shielding gas composition, post heat treatments, microstructure, and defects can significantly influence the mechanical properties of WAAM stainless steels. To achieve high quality WAAM stainless steel parts, there is still a strong need to further study the underlying physical metallurgy mechanisms of the WAAM process and post heat treatments to optimize the WAAM and heat t...

International Journal of Engineering Research and Technology (IJERT), 2014

https://www.ijert.org/the-effects-of-the-degree-of-deformation-in-the-work-hardening-process-on-microstructure-hardness-and-phase-transformation-of-the-material-structure-of-nickel-free-austenitic-stainless-steel https://www.ijert.org/research/the-effects-of-the-degree-of-deformation-in-the-work-hardening-process-on-microstructure-hardness-and-phase-transformation-of-the-material-structure-of-nickel-free-austenitic-stainless-steel-IJERTV3IS070086.pdf Stainless steel is one of the materials used for biomedical implants in medical field since it is resistant to corrosion under various environmental conditions, high plasticity, and has an excellent fatigue endurance and toughness. One such stainless steel used for biomedical implant is nickel-free austenitic stainless steel. In recent years, this material has been developed in medical field due to its low toxicity level in human bodies. Several methods have been used to improve the quality of nickel-free austenitic stainless steel and one of them is by using the work hardening method. Resulting data from the material test shows that the degree of deformation variation applied in work hardening process in the amount of 15 %, 30 %, 45 %, and 54 %, is able to change the grain structure and increase the material hardness significantly. The work hardening process is able to change the mechanical properties and the shape of the grain structure without changing the phase of the nickel-free austenitic stainless steel's crystal structure. Based on the X-Ray Diffraction (XRD) test, it can be concluded that the phase of the test specimen's crystal structure remains unchanged from its initial crystal structure, i.e. an austenitic phase with fcc (face centered cubic) crystal structure.

Procedia Engineering, 2014

Micro Plasma Arc Welding (MPAW) is one of the important arc welding process commonly using in sheet metal industry for manufacturing metal bellows, metal diaphragms etc. The paper focuses on weld quality characteristics like weld bead geometry, grain size, hardness and ultimate tensile strength of MPAW welded joints of various austenitic stainless steels namely AISI 316L, AISI 316Ti, and AISI 321. From the analysis carried out it is noticed that for the same thickness of work piece material and same welding conditions, AISI 304L has achieved sound weld bead geometry, highest tensile strength and hardness. However it is noticed that AISI 316L has attained lowest tensile strength, AISI 321 has lowest hardness and grain size.