Mario Ueda

New method of plasma immersion ion implantation and also deposition of industrial components using tubular fixture and plasma generated inside the tube by high voltage pulses

A new method of Plasma Immersion Ion Implantation (PIII) and deposition (PIII and D) for treating industrial components in the batch mode has been developed. A metal tubular fixture is used to allocate the components inside, around, and along the tube, exposing only the parts of each component that are to be ion implanted to the plasma. Hollow cathode-like plasma is generated only inside the tube filled with the desired gas, by applying high negative voltage pulses to the hollow cylindrical fixture which is insulated from the vacuum chamber walls. This is a very convenient method of batch processing of industrial parts by ion implantation, in which a large number of small to medium sized components can be treated by PIII and PIII and D, very quickly, efficiently, and also at low cost.

Effects of Plasma Immersion Ion Implantation (PIII) of Nitrogen on Hardness, Composition and Corrosion Resistance of Ti-6Al-4V Alloy

Ti-6Al-4V samples have been treated by PIII processing at different temperatures (400-800 o C), treatment time (30-150 min) and plasma potential (100 and 420 V). Hardness measurements results showed an enhancement of the hardness for all implanted samples. XRD results detected the Ti2N phase and the best corrosion resistance was found for the samples processed at higher temperature and lower PIII time.

Phase Transformations in Mechanically Alloyed and Sintered Ti-XMg-22Si-11B (X = 2 and 7 at.-%at) Powders

This work reports on effect of magnesium addition on the Ti6Si2B stability in Ti-xMg-22Si-11B (x = 2 and 6 at.-%) alloys prepared by high-energy ball milling and subsequent sintering. Ball milling was conducted under Ar atmosphere in stainless steel vials and balls, 300 rpm, and a ball-to-powder weight ratio of 10:1. Following, the powders milled for 10 h were axially compacted in order to obtain cylinder samples with 6 mm diameter. To obtain the equilibrium structures the green samples were sintered at 1100°C for 4 h under Ar atmosphere. X-ray diffraction, scanning electron microscopy and energy dispersive spectrometry were used to characterize the as-milled powders and sintered samples. Extended Ti solid solution were found in the Ti-2Mg-22Si-11B and Ti-7-Mg-Si-B powders milled for 20 min and 60 min, respectively, whereas an amorphous halo was produced on Ti-2Mg-22Si-11B powders milled for 420 min. The increase of Mg amount in the starting powder mixture has inhibited the Ti6Si2B formation in the mechanically alloyed and sintered Ti-7Mg-22Si-11B alloy.

High-Energy Ball Milling and Subsequent Heat Treatment of Ti-Cu-Si-B Powders

Metal matrix multicomponent alloys and others based on the Ti+Ti6Si2B phases are potentially attractive for structural applications. However, there is limited information in literature on the effect of alloying in stability of the Ti6Si2B compound, which presents its single-phase region close to Ti-22Si-11B alloy composition (at.-%). In this sense, this work discusses on the effect of copper addition on the stability of the Ti6Si2B compound. Elemental powder mixtures were used to prepare the Ti-xCu-22Si-11B (x=2 and 6 at.-%) alloys by high-energy ball milling and subsequent heat treatment (1100oC for 240 minutes). The as-milled Ti-Cu-Si-B powders and heat-treated samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). Similar behavior was noted during ball milling of Ti-Cu-Si-B powders, i.e., the Ti5Si3 phase was formed after milling for 180 minutes. The mechanically alloyed and heat treated Ti-2Cu-22Si-11B alloy presented a matrix of Ti6Si2B dissolving close to 2 at.-% Cu. Precipitates of Ti5Si3 and other unknown Cu-and Fe-rich phase were also identified in microstructures of these quaternary alloys, whose amounts were increased in the mechanical alloyed and heat treated Ti-6Cu-22Si-11B alloy.

Superficial Parameters Determination of the Ti-6Al-4V Alloy Submitted to PIII Treatment in Different Times of Implantation

The advancement of technology leads to the development of new materials improving their tribology properties. It can be noticed in different areas like aerospace industry, chemical and oil that need resistant material in high temperatures and aggressive environments. In this case, it is important to think in its tribological properties, like wear, oxidation, toughness, and hardness. An effective mean, economic and with easy application is the plasma immersion ion implantation (PIII) technique. In the case of difficult shapes, the material can be equally treated. In this work, the Ti-Al-4V alloy was submitted to PIII during 2 and 3 h. The comparative analysis to determine which of which time was more efficient related to the tribological improvement measured by Auger, X-ray diffraction and wear. It will be observed images by MEV of the alloy submitted to PIII treatment.

Comparation between Laser Surface Nitriding and Nitrogen Plasma Immersion Ion Implantation (N-PIII) on Creep Behavior of Ti-6Al-4V Alloy

Titanium alloys are widely used in machine building, aircraft manufacturing, medicine, motors, chemistry, and biomedicine due to their high strength-to-weight ratio, elasticity, corrosion resistance, and biocompatibility. In particular, Ti-6Al-4V containing (α + β) structure plays a very important role in aerospace industry in the manufacturing of components such as disks and blades for aircrafts turbines and structural forgings. However, one of the major factors limiting the life of titanium alloys in service is their degradation due to gaseous environments, in particular, to environments containing oxygen at elevated temperatures during long-term use. The sensitivity of titanium alloys to high-temperature exposure is a well-known phenomenon. When titanium alloys are heated to temperatures above approximately 800oC, oxygen, hydrogen and nitrogen can penetrate into them. The penetration of these elements increases hardness and brittleness while decreasing the toughness of the alloy. Laser surface nitriding is a technique used to modify the near-surface microstructure and/or composition by melting the surface using a high-power laser beam with reactive gas as a shrouding environment, forming a nitride layer on the surface of Ti–6Al–4V to improve the alloy’s tribological and mechanical properties. The results of laser gas nitriding of Ti–6Al–4V showed a significant increase of microhardness and enhanced erosion resistance significantly compared with untreated Ti–6Al–4V, since the nitride layer acts as a diffusion barrier for inward oxygen diffusion into the alloy, reducing the contribution of oxygen dissolution in the substrate to the total mass gain. Other important technique that was developed for the beneficial modification of surface sensitive properties is Nitrogen Plasma Immersion Ion Implantation N-PIII. A sample is immersed in plasma and subjected to negative high-voltage pulses. In the electrical field, the ions are accelerated to high energies and incorporated into the sample. Enhancing of the hardness and wear process of the materials due to the N-enriched layer caused by diffusion of N in the sample at PIII process can be expected. Both techniques provide an improvement in the creep resistance. The objective of this work was evaluating the creep resistance of the Ti-6Al-4V alloy with superficial treatments of laser nitriding and Nitrogen Plasma Immersion Ion Implantation N-PIII in creep test of Ti-6Al-4V alloy. It was used Ti-6Al-4V alloy as cylindrical bars under forged and annealing of 190 oC by 6 hours condition and cooled by air. The Ti-6Al-4V alloy after the superficial treatment of laser nitriding and N-PIII was submitted to creep tests at 600 oC in the stress of 250 MPa and 319 MPa, under constant load mode. The creep parameters are determined and a comparative analysis is established with the results gotten from the alloy with both treatments. The laser nitrided has showed an improved creep behavior compared with the same alloy with N-PIII coating, with a reduction in the creep rate and increasing the creep lifetime.