Kay C.M.,ASB Industries Inc.
Advanced Materials and Processes | Year: 2013
Product quality, maintenance costs, and production requirements drive engineering improvements where surfacing technologies play an important role in steel production. Areas of concern during steel manufacturing include heat, corrosion, and wear. To enhance equipment life, a number of thermal spray coatings are being used. Friction, grip, and long-wearing surfaces allow proper strip tension from the initial weld joining to final trimming and wrapping. Rolls with HVOF-applied carbide coatings have harder surfaces than strip materials. Optimized surface profiles and high friction coefficients support gripping of strips to rolls without harming the strip s surface finish properties. The most commonly used zinc baths consist of galvanized zinc with minor concentrations of aluminum. Coatings use tungsten carbide/cobalt powders applied via HVOF or detonation gun technology. Success of these coatings depends on the spray parameters, powder manufacturing method, and sealant system. The key to increased life is to reduce the amount of free cobalt in the coating. Source
Bala N.,Baba Banda Singh Bahadur Engineering College |
Singh H.,Indian Institute of Technology Ropar |
Prakash S.,Indian Institute of Technology Roorkee |
Karthikeyan J.,ASB Industries Inc.
Journal of Thermal Spray Technology | Year: 2012
High temperature corrosion accompanied by erosion is a severe problem, which may result in premature failure of the boiler tubes. One countermeasure to overcome this problem is the use of thermal spray protective coatings. In the current investigation high velocity oxy-fuel (HVOF) and cold spray processes have been used to deposit commercial Ni-20Cr powder on T22 boiler steel. To evaluate the performance of the coatings in actual conditions the bare as well as the coated steels were subjected to cyclic exposures, in the superheater zone of a coal fired boiler for 15 cycles. The weight change and thickness loss data were used to establish kinetics of the erosion-corrosion. X-ray diffraction, surface and cross-sectional field emission scanning electron microscope/energy dispersive spectroscopy (FE-SEM/EDS) and x-ray mapping techniques were used to analyse the as-sprayed and corroded specimens. The HVOF sprayed coating performed better than its cold sprayed counterpart in actual boiler environment. © 2011 ASM International. Source
Singh H.,Guru Nanak Dev University |
Karthikeyan J.,ASB Industries Inc.
Journal of the Brazilian Society of Mechanical Sciences and Engineering | Year: 2013
Cold spray is one of the various names for describing an all-solid-state coating process that uses a high-speed gas jet to accelerate powder particles toward a substrate where they plastically deform and consolidate upon impact. Traditional thermal spray coating technologies require the melting or partial melting of feedstock material, and then quenching the molten droplets to produce coating. Cold spray technology belongs to the wide family of thermal spray technology and is a future of deposition of coating especially on temperature sensitive materials. In this paper the historical background of the cold spray process, fundamentals of this process and influence of the process parameters on coating properties are summarized. The main motivation for this review is to summarize the rapidly expanding common knowledge on cold spray for the researchers and engineers already or soon to be involved for their future endeavors with this new technology. © The Brazilian Society of Mechanical Sciences and Engineering 2013. Source
Lahiri D.,Florida International University |
Gill P.K.,Florida International University |
Scudino S.,Leibniz Institute for Solid State and Materials Research |
Zhang C.,Florida International University |
And 5 more authors.
Surface and Coatings Technology | Year: 2013
Al-based glassy coatings were synthesized using cold spraying technique to protect 6061 aluminum surface from wear and corrosion. Gas atomized Al90.05Y4.4Ni4.3Co0.9Sc0.35 (at.%) powder was used as the starting powder. Dense (98%) coatings with a uniform thickness of ~250μm were deposited. The coatings retained the glassy structure of the powder with few nanocrystals embedded in the amorphous matrix. Ball-on-disk wear of the coatings showed 600% improvement in the wear resistance as compared to 6061Al substrate. Potentiodynamic studies of the coatings in varying NaCl concentrations displayed 5 times better corrosion resistance than 6061 Al substrate, which was attributed to the active passivation and the chemical homogeneity of the coatings.© 2013 Elsevier B.V. Source
Einarsson J.I.,ASB Industries Inc.
Obstetrics and Gynecology | Year: 2011
Objective: In a 3-year period, the main mode of access for hysterectomy at Brigham and Women's Hospital changed from abdominal to laparoscopic. We estimated potential effects of this shift on perioperative outcomes and costs. Methods:We compared the perioperative outcomes and the cost of care for all hysterectomies performed in 2006 and 2009 at an urban academic tertiary care center using the χ test or Fisher's exact test for categorical variables and two-sided Student's t test for continuous variables. A multivariate regression analysis was also performed for the major perioperative outcomes across the study groups. Cost data were gathered from the hospital's billing system; the remainder of data was extracted from patients' medical records. Rssults: This retrospective study included 2,133 patients. The total number of hysterectomies performed remained stable (1,054 procedures in 2006 compared with 1,079 in 2009) but the relative proportions of abdominal and laparoscopic cases changed markedly during the 3-year period (64.7% to 35.8% for abdominal, P<.001; and 17.7% to 46% for laparoscopic cases, P<.001). The overall rate of intraoperative complications and minor postoperative complications decreased significantly (7.2% to 4%, P<.002; and 18% to 5.7%, P<.001, respectively). Operative costs increased significantly for all procedures aside from robotic hysterectomy, although no significant change was noted in total mean costs. CONCLUSION:: A change from majority abdominal hysterectomy to minimally invasive hysterectomy was accompanied by a significant decrease in procedure-related complications without an increase in total mean costs. © 2011 The American College of Obstetricians and Gynecologists. Source