Developing a Medicinal implants or devices is a challenging task for the researchers, right from the selection of materials, design, bio-compatibility and implantation to the host tissue. At every stage it requires proper care in processing of medical implants. In recent years the demand for medical implants had grown rapidly due to the awareness in the society. Major share of implants is used by younger people as they are active in sports, motor vehicle accidents leads to facture. Even older people also preferring to implants for ease of living. The commonly used implants are, prosthetic joints, knee replacement, dental, maxillofacial reconstructions etc.There is huge demand for the medical implants in coming years, presently a few bio-materials available for implant devices such as Ti-alloys, Stainless steel and Co-Cr-Mo alloys. There a scope to the researchers to develop a new alloy that are bio-compatible in nature and bring down the cost of the implant procedure to the needed patients. In this context additive manufacturing (AM) is an advanced manufacturing technology emerging as prominent technique in medical fields. Laser Engineered Net ShapingTM (LENS) is one such metal additive technique which provides fabrication of parts with the help of laser power, melts the powder alloy completely and builds parts layer by layer directly from the CAD model.In the present study, samples are fabricated from LENS process and carried the In-Vitro and In -Vivo bio-compatible tests as cytotoxicity and sub chronic toxicity to verify the toxicants release and their sustainability as the medical implants by the LENS deposited Co-Cr-W alloy samples. From the studies it is observed that the alloy samples show acceptable result. MTT assay demonstrate that cell viability is better in Osteoblast cells compared to the Fibroblast cells. Osteoblast cells show slightly more viable to the cell treatment on the samples during the experimental period. Sub chronic toxicity conclude that LENS deposited Co-Cr-W alloy is not toxic in all the rats studied herein and did not produce any toxic signs or evident symptoms. LENS deposited Co-Cr-W alloy did not cause any lethality or produce any relative body organs weight and haematological studies didn’t show adverse effects.
Fused Deposition Modeling (FDM) is one of the best Rapid Prototyping Processes proved to be. Many researchers have produced a lot of work using the FDM process and many papers were published. Many researchers have concentrated on optimizing the parameters to obtain higher surface finish. Burnishing is one of the processes used to get higher surface finish on light metals. The present paper deals with the application of burnishing process on the samples fabricated with FDM. The burnishing process is applied on the samples at different speeds and the surface finish results are recorded in the present experimentation.
Metallic materials are generally characterized by the evaluation of hardness and wear resistance of the material at the specified condition. The characterization is necessary for understanding the behavior of the metals, especially alloys, at different conditions. To study the effect of heat treatment on weld deposited Co-Cr-Mo alloy, arc welding process has been used to prepare the samples.Using L9 Orthogonal array of Taguchi method, the samples, in three groups,are heat treated by solution at 1200 o C for 30, 45 and 60minutes followed by water quenching. Two sets of the samples from each groupare aged at 815 o C and 830 o C for 2, 4 and 6 hours. All the samples are then tested for their hardness andwear resistances. Microstructure analysis has been carried out from SEM images of the samples. The experiment results reveal that the differences in heat treatment did not influence the grain size of the samples, but the precipitation of carbides varies from sample to sample. The CoCr-Mo alloy samples solutionized at 1200 o C for 60minutes have exhibited high hardness (371.6±2Hv) and wear resistances. For high hardness and wear resistance, high solution time is required. ANOVA has been carried out to identify the best parameters of heat treatment. Key words: Co-Cr-Mo; welddeposition;solution heat treatment; ageing;microstructure; hardness; wear resistance ____________________________________________________________________________________________________ INTRODUCTIONCharacterization of a material is done generally by conducting a series of tests on the material like hardness, wear resistance and microstructure analysis. The behavior of Co-Cr-Mo alloy was also analyzed at different conditions of the material samples.The results of the experiments conducted on Nickel and Carbon free Co-Cr-Mo alloy by applying heat treatment followed by hot forging process reveal that the yield strength of the material decreases with increase in heat treatment temperature and time [1].The optimal results of mechanical properties were obtained at an ageing temperature of 815 o C for 4 hours and solution at 1120 o C for 1 hour on as-cast Co-Cr-Mo samples. The mechanical tests showed that an excessive time of dissolution reduces Ultimate Tensile Strength [2]. Dense components of Co-Cr-Mo were fabricated using laser deposition method, by optimizing the process parameters.The carbide volume fraction and the hardness were comparable with wrought material, but the abrasive wear resistance of laser deposited samples was less [3].Thephase and shape of the carbide precipitates depend on the carbon content and the type of heat treatment. Shingo Meneta et al have tested ASTM 75 confirming CoCr-Mo alloy samples with four different carbon contents for their microstructures after applying solution heat treatment in the temperature range of 1200 o C to 1275 o C for the time periods of 0 to 12hours. A new π phase has been identified in the alloys with carbon content 0.15, 0.25 and 0.35 mass percentage, after heat treatment at high temperature (...
Present investigation is devoted to study the effects of aqueous solution of 3.5% NaCl on high-cycle stress life and fatigue crack growth behavior of 7475-T7351 alloy. At low alternating stress the environment test exhibited corrosion pit dominated crack initiation and at high stress level crack initiation occurred through anodic dissolution. Corrosive environment resulted reduction in fatigue life, crack growth rate enhancement and drop in stage-I to stage-II transition. The behavior is explained with the help of fractographic observations.
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