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Abstract: In this study, the nickel alloying and austempering effects on corrosion behavior of ductile irons were investigated. The microstructure of austempered ductile iron (ADI) was analyzed by XRD, and the polarization corrosion tests were conducted using 3.5wt.% NaCl solution. The results showed Ni-alloyed as-cast has less nodule counts than the unalloyed one; therefore, the former is more corrosion resistant than the latter. For the ADI, the nickel addition increases the retained austenite content, resulting in having better corrosion inhibition than the unalloyed ADI. Comparatively, the order of corrosion resistance in 3.5wt.% NaCl solution is as follows: 4%Ni–ADI>ADI>4%Ni–DI>DI. [Copyright &y& Elsevier]

Abstract: This study utilized electroless nickel (EN) and cathodic arc evaporation (CAE) technologies, with the known advantage of low processing temperature (EN=90 °C and CAE=230 °C), to treat the austempered ductile iron (ADI) substrate. The eligibility of applying the EN and CAE–CrTiAlN duplex coatings on ADI, along with the coating properties, such as structure, roughness, and adhesion, were evaluated and analyzed. Moreover, polarization and immersion tests were performed to further understand the effects of the coatings on the corrosion resistance of ADI. The results showed that the unique microstructure of ADI did not deteriorate after EN and CAE treatments. With regard to corrosion resistance, the duplex coated specimens performed better than did the uncoated and monolithic EN or CrTiAlN coated ones in 3.5 wt.% NaCl and 10 vol.% H2SO4 aqueous solutions. [Copyright &y& Elsevier]

Abstract: In this study, Cr2O3/CrN double-layered coatings synthesized by the cathodic arc plasma deposition were evaluated for potential application in injection molding dies. The double-layered coatings were designed with CrN of constant thickness as an interlayer and Cr2O3 of various thickness as a surface layer. Cr2O3 coatings of different thickness were deposited at varied times under the mixture of N2 and O2 at a constant flow rate. Well-adherent Cr2O3/CrN double-layered coatings were identified using scratch test and Rockwell C indention test. Characteristics of Cr2O3/CrN double-layered coatings were investigated by using XRD, XPS, SEM, tribological tests, and water contact angle measurement. The XRD analysis showed an increasing peak intensity of the Cr2O3 phase as the thickness of the top layer increased. The double-layered coatings exhibited an enhanced hardness of 32GPa comparable to that of CrN (20GPa). The tribological property of Cr2O3/CrN double-layered coatings also compared favorably with that of CrN film. The water contact angle measurement revealed that Cr2O3/CrN double-layered coatings were 40% higher than CrN film. [Copyright &y& Elsevier]

Abstract: Because of its low cost, high tensile strength, fatigue resistance, and wear resistance, austempered ductile iron (ADI) has been utilized in a wide variety of mechanical applications. However, in opposition to the versatility of the above-mentioned mechanical properties, the shortcomings of ADI are its surface hardness (Hv: 396) and corrosion resistance. And, because its relatively low austempering temperature falls in the range of Ms–450°C (Ms: the martensite start temperature), ADI cannot be case hardened using traditional high temperature heat treatment. This study explored the effects of TiN and TiAlN coatings on ADI, with respect to surface hardness and corrosion resistance. The process employed for coating TiN/TiAlN onto ADI involved variable target current low temperature cathodic arc deposition (CAD). The coating characteristics and corrosion resistance of TiN/TiAlN-coated ADI were analyzed for further understanding of the feasibility of the low temperature CAD coating process. The analysis showed that TiN and TiAlN films could successfully be coated onto ADI through CAD technology without altering the unique microstructure of ADI. Utilizing a variety of target currents in the coating process yielded an acceptable level of adhesion while raising the surface hardness of ADI by a factor of 2–4 (Hv: 396 versus 1356–1910). It was observed that as target current increased, the surface roughness of the specimens also increased. TiN/TiAlN-coated ADI specimens exhibited higher corrosion resistance than uncoated ones when both were immersed in separate solutions of both 3.5wt% NaCl and 10vol.% HCl. Conclusively, the application of TiN and TiAlN films to ADI through the coating process of low temperature CAD is a viable surface modification for ADI applications that require increased surface hardness and corrosion resistance. [Copyright &y& Elsevier]

Abstract: Austempered ductile iron (ADI) is an austemper-treated ductile iron with acicular ferrite and high-carbon austenite as the matrix of microstructure. In general, the austempering is isothermally treated about in the temperature range from M s to 450°C, thus the traditional case hardening of high temperature cannot be available to treat ADI. In recent years, physical vapor deposition (PVD) technique using lower processing temperature has been widely adopted to coat various films, such as diamond-like carbon (DLC), CrN, TiN and so on, on the engineering material for surface modification. In particular, DLC film possesses excellent mechanical properties such as high hardness and low friction coefficient. Electroless nickel (EN), another lower temperature coating process, has also a wide field of application such as the industrial components and machine parts. Thus, the purpose of this study is to investigate the effect of EN and PVD–DLC surface coatings on mechanical behaviors of ADI, especially the tensile and fatigue properties. Analyses of the resulting films were also performed for correlating the mechanical properties attained to the coating characteristics. [Copyright &y& Elsevier]

Cr(N,O)/CrN double-layered coatings synthesized by cathodic arc evaporation (CAE) process have been evaluated for a potential application in injection molding dies. The double-layered coatings were designed with CrN as an interlayer and Cr(N,O) as a surface layer. The Cr(N,O) coatings were deposited under the mixture of constant flow of N2 and various flows of O2. Well-adhered Cr(N,O)/CrN double-layered coatings were identified using a scratch test. The characteristics of the Cr(N,O)/CrN double-layered coatings were investigated by using XRD, SEM, tribological tests and water contact angle measurement. The XRD analysis shows Cr2O3 phase in the surface layer as the oxygen is introduced up to 46 sccm. The double-layered coatings exhibit an enhanced microhardness of 23 GPa comparable to CrN of 18.5 GPa. The tribological performance of the Cr(N,O)/CrN double-layered coatings also compares favorably with that of the CrN film. The water contact angle measurements revealed Cr(N,O)/CrN double-layered coating exhibited higher contact than CrN film. [Copyright &y& Elsevier]

This study torrefied Ananas comosus peel (ACp) and Annona squamosa peel (ASp) samples at different temperatures (210–300 °C) for different durations (30 and 60 min) to produce biochar as a renewable energy source. Analysis results indicated that the torrefaction temperature, not the reaction duration, had a dominant influence on the characteristics of the produced biochar. The ACp biochar had a maximum higher heating value (HHV) of 27.7 MJ/kg and maximum energy density of 1.58, which were higher than those of the ASp biochar. As the torrefaction temperature and time increased, the fixed carbon and ash contents and the fuel ratio (FR) increased gradually for both types of biochar, but the volatile matter content and energy return on investment (EROI) decreased. The hydrogen/carbon and oxygen/carbon atomic ratios of both types of biochar are comparable to those reported for lignite. Thermogravimetric and derivative thermogravimetric analyses confirmed that the thermal stability of both types of fruit waste increased considerably with the torrefaction temperature. Furthermore, the ACp biochar had a maximum EROI of 22.9 and FR of 0.36. When 10%–20% biochar was cofired with 80%–90% bituminous coal in a power plant, the FR (1.80–1.84 and 1.60–1.67)—representing combustion efficiency—approximated that of bituminous coal (1.5–2.5), but greenhouse gas (GHG) emissions decreased significantly (83.7%–94.3%). Taken together, the cofiring of ACp biochar or Asp with coal is potentially viable and economically beneficial for increasing the HHV, energy density, fixed carbon content, FR, and EROI of these materials while reducing GHG emissions, rendering these materials suitable for partially replacing bituminous coal in power plants. Image 1 • Torrefaction of Ananas comosus and Annona squamosa peel to environmentally friendly biochar. • The higher heating value of both biochar increased to 19.1–27.7 MJ/kg after torrefaction. • The high energy return on investment of 10.9–22.9 confirmed the feasibility of the produced biochar for renewable energy. • The application of biochar for partial coal substitution can reduce 83.7–94.3% CO 2 emissions. [ABSTRACT FROM AUTHOR]

Abstract: TiN and CrN single layer thin films along with TiN/CrN multilayer thin film, which has an average layer thickness of 4nm were deposited on WC substrates by a commercially used unbalanced DC magnetron sputtering. The microstructure and mechanical properties of the as-deposited films were investigated. The TiN/CrN multilayer thin film has a single phase structure with the preferential orientation of (200), a finer surface morphology and a finer columnar crystal structure. Additionally, the TiN/CrN multilayer thin film also shows better adhesion on substrate and hardness than the single layer thin films. The hardness of the annealed multilayer thin film is slightly increased after annealed at temperatures of 600–800°C. This is attributed to the increased intensity of (111) reflection during annealing. [ABSTRACT FROM AUTHOR]

Physical vapor deposition (PVD) coatings such as TiN and chromium nitride (CrN) have been successfully applied in metal forming industries for their excellent wear resistance. There has been interest in applying such coatings to the molding dies in order to reduce the coefficient of friction and extend die life. When applied to cast liquid Al and Al alloy into molded parts, die casting and injection molding technologies faced harsh conditions such as erosion, corrosion, creep and thermal fatigue. In this study, Cr2O3/CrN duplex coatings synthesized by PVD processes were evaluated for potential applications in molding dies. Cr2O3/CrN thin films of 3-μm thickness were deposited using cathodic-arc evaporation. By using X-ray diffraction, scanning electron microscopy, wear tests, TGA/DTA analysis and molten Al-alloy dipping tests, the performance of Cr2O3/CrN duplex coatings was investigated. The results demonstrated low frictional coefficient of Cr2O3/CrN thin films and oxidation resistance of 900 °C in ambient atmosphere. Due to low coefficient of friction, oxidation resistance and corrosion resistance in Al-alloy melt, Cr2O3/CrN duplex coating was promising for molding die applications. [Copyright &y& Elsevier]