Mechanical and Metallurgical Properties of Various Nickel-Titanium Rotary Instruments

The aim of this study was to investigate the effect of thermomechanical treatment on mechanical and metallurgical properties of nickel-titanium (NiTi) rotary instruments. Eight kinds of NiTi rotary instruments with sizes of ISO #25 were selected: ProFile, K3, and One Shape for the conventional alloy; ProTaper NEXT, Reciproc, and WaveOne for the M-wire alloy; HyFlex CM for the controlled memory- (CM-) wire; and TF for the R-phase alloy. Torsional fracture and cyclic fatigue fracture tests were performed. Products underwent a differential scanning calorimetry (DSC) analysis. The CM-wire and R-phase groups had the lowest elastic modulus, followed by the M-wire group. The maximum torque of the M-wire instrument was comparable to that of a conventional instrument, while those of the CM-wire and R-phase instruments were lower. The angular displacement at failure (ADF) for the CM-wire and R-phase instruments was higher than that of conventional instruments, and ADF of the M-wire instruments was lower. The cyclic fatigue resistance of the thermomechanically treated NiTi instruments was higher. DSC plots revealed that NiTi instruments made with the conventional alloy were primarily composed of austenite at room temperature; stable martensite and R-phase were found in thermomechanically treated instruments.

Recrystallisation of Magnesium Alloys Containing Rare-Earth Elements

The static recrystallisation behaviour of two magnesium alloys after hot rolling have been examined. The alloys chosen for study were the conventional alloy AZ31, and an alloy containing the rare earth element Gadolinium. The recrystallisation kinetics were lower for the rare-earth alloy at low annealing temperatures, but at high annealing temperatures the kinetics were higher for the rare-earth alloy. It is suggested that this change in the comparative recrystallisation kinetics is a result of the improved mobility of the rare-earth solute at higher temperatures. This affects the recrystallisation kinetics through solute partitioning to the grain boundaries. The effect of this segregation on the recrystallisation texture is also discussed.

Manufacture, Wet and Dry Corrosion, and Plasma Nitridation of Novel Nanocrystalline Ni-Cr Nanoparticle Nanocomposites: A Brief Review

The paper is a short review of the fabrication, wet and dry corrosion, as well as plasma nitridation of novel Ni-Cr nanocomposites. The nanocomposites, fabricated by co-electrodeposition of Ni and nanometer-sized Cr particles, have the nanocrystalline Ni matrix dispersing the second phase of nanoparticles. They, compared to conventionally coarse-grained Ni-Cr alloys, exhibit dramatically increased resistance to liquid corrosion in a 3.5% NaCl solution, and to hot corrosion under molten salt of Na2SO4-Na2SO4-NaCl at 700oC. The reason for these is correlated with the unique structure of the nanocomposite, which guarantees the fast diffusion of chromium from the composite interior to the corrosion front for the formation of a continuous, protective layer of chromium oxide-rich films severing the composites from environmental corrosive species. During plasma nitridation at 560oC the Ni-Cr nanocomposite forms a thick nitriding layer which cannot be achieved on the conventional alloy counterpart with a comparable composition, due to enhanced nitridation kinetics.

SUPERKORE

U. S. S. SUPERKORE comprises a series of six low alloy, deep hardening carburizing steels that have shown hardenability equal to or slightly greater than the conventional alloy steels which they are designed to replace, as shown under General Characteristics. This datasheet provides information on composition, hardness, and tensile properties as well as fracture toughness. It also includes information on heat treating, machining, and joining. Filing Code: SA-10. Producer or source: United States Steel Corporation.