Naotake Niwa

In situ synthesis of titanium-aluminides in coating with supersonic free-jet PVD using Ti and Al nanoparticles

This paper presents supersonic free-jet PVD (SFJ-PVD) as a new coating technology for structural materials. In SFJ-PVD, coating film is formed by high velocity impact of solid nanoparticles to base materials. This method is composed of evaporation and deposition processes. In the evaporation process, the source material evaporates to form nanoparticles in an inert gas atmosphere. In the deposition process, nanoparticles are deposited on base materials to form coating film with supersonic gas flow. The gas flow is generated by pressure difference between the evaporation chamber and the deposition chamber. The flow of the gas is accelerated through a specially designed supersonic nozzle at the supersonic flow of 3.6 Mach number. With SFJ-PVD, mixed Ti and Al nanoparticles produce high-density coatings of titanium-aluminides without voids and cracks. They synthesize titanium-aluminides on the substrate at 800 K.

Mechanical properties of a Ti15V3Cr3Sn3Al alloy affected by the impurity hydrogen

Abstract The effect of hydrogen on the tensile properties of a β titanium alloy (Ti 15V 3Cr 3Sn 3Al) has been studied. Cold-rolled specimens and specimens charged with hydrogen (annealed at 500°C for 1 h at atmospheric pressure of hydrogen gas) were solution-treated at 800°C for 1 h, water-quenched and subsequently aged at 510°C. Significant retardation in the age-hardening characteristics of the alloy occurred by the hydrogen charging. The effect of hydrogen charging on the ductility was not found except in the as-solution-treated condition, where slight decrease (from 65% to 60%) in the reduction in area by the charging was detected. However, when tensile tests were carried out using a unique testing machine equipped with an ultra high vacuum chamber and a quadrupole mass spectrometer, a large amount of hydrogen gas was evolved from the specimen at the moment of fracture. Furthermore, the ductility of the uncharged specimen was improved with a reduction in the hydrogen content. Thus it can be concluded that the impurity hydrogen even at the uncharged level has a strong correlation with the fracture and causes a deleterious effect on the ductility.

Fabrication of nanostructure composites in functionally graded coatings with supersonic free-jet PVD

Graded Al/AlTi and Al/Al-Si coatings are prepared by depositing nanoparticles with supersonic free-jet PVD (SFJ-PVD). The SFJ-PVD has been developed as a new coating method in which a coating film is formed by depositing nanoparticles with very high velocity onto a substrate. The high velocity of nanoparticles is produced by the supersonic gas flow of inert gas. A smooth, compact and defect-free microstructure is formed both at the interface between substrates and coating films and inside the coating films. The microstructures of Al/AlTi and Al/Al-Si coating films have very fine grain size. Mixing Ti and Al nanoparticles by depositing them onto a substrate produces in-situ syntheses of g-TiAl and a2-Ti3Al intermetallic compounds on the substrate. It is confirmed with nano-indentation hardness tester that graded coatings have graded hardness corresponding to the gradation of composition.

In-vitro study on apatite/titanium composite coatings with supersonic free-jet PVD

Abstract Hydroxyapatite (HAp) has many applications in the medical field. The objective of this study is to produce HAp/Ti composite coating with Supersonic Free-Jet PVD (SFJ-PVD). The SFJ-PVD is a technique to deposit nanoparticles with supersonic gas flow and to form a thick coating film. In a gas evaporation chamber, a source material is evaporated to form nanoparticles in an inert gas atmosphere. The nanoparticles are then carried to a substrate in a deposition chamber with an inert gas flow through a transfer pipe. The gas flow is generated by the pressure difference between the chambers and accelerated to the supersonic flow of 4.2 Mach through a specially designed supersonic nozzle. With SFJ-PVD, we obtain a uniform high-density HAp/Ti composite coating. XRD analysis reveals that the composite coating is composed of Ti and HAp. An in vitro study was carried out to investigate the bioactivity of the HAp/Ti composite coating under simulated body fluid.

Coating with supersonic free-jet PVD

Recently, requirements for structural materials become increasingly severe. A coating is one of the most promising methods to achieve the requirements. However, conventional coating processes generally have technical problems. We apply Supersonic Free-Jet PVD (SFJ-PVD) to coating. The SFJ-PVD is a technique to deposit nanoparticles with supersonic gas flow and to form a thick coating film without a crack or a void. This method is composed of “gas evaporation” and “vacuum deposition”. In a gas evaporation chamber, a source material is evaporated to form nanoparticles in an inert gas atmosphere. The nanoparticles are then carried to a substrate in a deposition chamber with an inert gas flow through a transfer pipe. The gas flow is generated by the pressure difference between the chambers and accelerated through a supersonic nozzle. With SFJPVD, We obtain uniform several hundreds micron meter-thick, high-density coatings.

Fabrication of Apatite/Titanium Functionally Graded Coating Using Supersonic Free-Jet PVD

Hydroxyapatite (HAp) is very attractive in medical field. The objective of this study is to produce HAp/Ti composite coating with Supersonic Free-Jet PVD (SFJ-PVD). The SFJ-PVD is a technique to deposit nanoparticles with supersonic gas flow and to form a thick coating film. In a gas evaporation chamber, a source material is evaporated to form nanoparticles in an inert gas atmosphere. The nanoparticles are then carried to a substrate in a deposition chamber with an inert gas flow through a transfer pipe. The gas flow is generated by the pressure difference between the chambers and accelerated to the supersonic flow of 4.2 Mach through a specially designed supersonic nozzle. With SFJ-PVD, we obtain a uniform high-density HAp/Ti composite coating. XRD analysis reveals that the composite coating is composed of Ti and HAp. An in-vitro study was carried out to investigate the bioactivity of the HAp/Ti composite coating under simulated body fluid.