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In cold spray, the interactions between feedstock particles and propellant gas control deposition outcome. The particle impact temperature, along with impact velocity, governs the deposition due to its effect on the impact deformation processes. As bonding mechanisms rely primarily on the particle/substrate plastic flow upon impact, particle impact temperature holds a predominant role in process optimization. The current work studies the effect of pure aluminum particle impact temperature on deposition phenomena when propelled onto a hard steel substrate. Particle impact temperature was varied while achieving the same particle impact velocity, using low and high-pressure cold spray systems. Three different particle diameters are studied, with varying resulting inherent impact temperatures, to provide size dependent insight on deposition/adhesion. Experimental results demonstrate that at low particle impact temperature, i.e. 50 °C, coating adhesion is controlled by in-situ peening. Adhesion shifts to particle in-flight characteristics dependent bonding, i.e. η = V/Vc, as particle temperature increases. At low particle impact temperatures, the coating bond strength increases with increasing in-situ impingement intensity and frequency, i.e. decreasing deposition efficiency with increasing particle size. At higher particle impact temperatures, in-situ peening rate decreases and the adhesion strength increases with decreasing particle size. In addition to affecting the impact process (DE, Vc and adhesion), the particle impact temperature also influences the coating mechanical properties through the creation of temperature-dependent crack propagation mechanisms, i.e. deflection, bridging and acceleration, and of particle-particle structural arrangement related to deformation processes, i.e. fish scale effect and pseudo-plasticity behavior.

The recent development of the cold spray method has made it possible to deposit dense coating with good adhesion and with almost no change in the microstructure, which is promising in repairing damaged Al-based aircraft skin. In this work, the in-situ shot-peening-assisted low-pressure cold spray method was used to deposit Al-based dense coatings with good mechanical and corrosion protection properties on AA 2024-T3 alloy. The detailed microstructure, coating adhesion, and corrosion protection performance were systematically investigated. A dense microstructure with low porosity ( 45 MPa) is achieved for the coatings. By comparison, Al 5083 coating exhibited the optimum mechanical properties. The Al and Al 5083 coatings reveal similar pitting resistance and repassivation ability. During long-term immersion test (>480 h) the corrosion resistance of Al 5083 coating surpassed that of CP Al coating. In conclusion, Al 5083 coating has a good combination of mechanical and anti-corrosion properties.

Ni based coatings are being used to protect metallic engineering components in extreme conditions. Cold gas dynamic spray, or simply cold spray, is receiving increased attention during the last years because of the lower spraying temperature required to deposit metallic coatings. Further improvements in the coatings' performance could be attained by laser glazing to enhance coating adhesion and oxidation resistance. For these reasons, the aim of this work is to analyze the viability of cold spray to process Inconel 625 coatings and to evaluate the effect of laser remelting on their mechanical properties.

Ti–15V–3Al–3Cr–3Sn (Ti–15–3) is one of the important practical titanium alloys with high cold deformability and high mechanical strength, but its wear resistance is poor. This paper reports the formation of wear-resistant and adhesive ceramic coatings on Ti–15–3 by two-step plasma electrolytic oxidation (PEO). The PEO of Ti–15–3 has been carried out first in alkaline aluminate electrolyte to form a wear-resistant oxide layer and then in acid electrolyte containing both phosphoric acid and sulfuric acid to improve adhesion of the coating. The coating formed in the alkaline aluminate electrolyte is more than 10 μm thick, and highly crystalline. The main phase is Al2TiO5. This coating shows high wear resistance, but is not adherent to substrate due to the development of a number of voids and pores in the oxide layer close to the substrate. A new oxide layer with amorphous structure is formed next to the substrate in the subsequent PEO in the acid electrolyte, during which the voids are filled with a new oxide formed in the acid electrolyte, reducing the porosity. As a consequence, the adhesion of the coating is markedly improved without deteriorating the high wear resistance.

Up to now the action of heating and cleaning of wire have been carried out successively in large complex machines, whereby the heating is performed by a gas flame or electrical current and the cleaning is done chemically or ultrasonically. One advantage of the “3-in-1” Plasma Wire System is that heating and cleaning of the wire can be accomplished simultaneously by the plasma. Furthermore, with plasma treatment the surface of the wire can be activated. In addition, the “3-in-1” Plasma Wire System is very compact and requires up to 70% less space than other systems. The application is more economical because there is no need to heat any chemical bath with an electrical current.

This paper reports on the mechanisms taking place in the variation of surface structure of cermet substrates and their influences on coating adhesion as well as wear behaviour of newly developed PACVD–TiN-coated cermets. The topics considered are the relationships between the surface properties of the substrate and performance of the coated tools. Therefore, investigations were carried out to determine coating adhesion, residual stress measurements and machinablity tests. Face milling experiments were carried out in terms of performance and wear behaviour of these tools.

Cermets are the link between the hard but brittle ceramic cutting tools and the tough but less wear resistant cemented carbides. As Cermets are less tough than WC-based cemented carbides, limitations are given concerning the feed rate. In order to avoid these limit PACVD-coated Cermets with different layer systems have been developed. Apart from TiN and Ti(C,N)-singlelayers, multilayers consisting of TiN, Ti(C,N) and TiC layers were deposited in different layer thicknesses and sequences. This report describes the structure and the coating adhesion by scratch tests of the layer systems. Milling tests with PACVD-coated Cermet cutting tools were carried out in terms of performance and wear behaviour of these tools.

The adhesion of amorphous hydrogenated carbon (a-C:H) films deposited in a radio frequency (r.f.) plasma discharge on stainless steel, alumina and cemented carbide with different intermediate layers (Ni, Ti and TiC) and sputter cleaning procedures was studied. The composition of the carbon films and the intermediate layers as well as the interface between the coating and the substrate was determined by secondary ion mass spectroscopy (SIMS). The adhesion experiments were carried out using a scratch tester. Tested specimens were also studied by scanning electron microscopy (SEM) to reveal the morphology of the coatings and the scratches.Without any intermediate layer, the a-C:H coatings generally had insufficient adhesion to the substrate materials studied. For stainless steel and cemented carbide substrates, the TiC intermediate layer and, for alumina substrates, the titanium intermediate layer gave the best adhesion values evaluated by the scratch test. Also, the sputter cleaning of the substrates prior to deposition was necessary for sufficient adhesion of the coating. The intermediate layers also change the failure mode of the coating in the scratch test in some cases.

WTCM,SCI & TECH CTR METALWORKING IND,B-3590 DIEPENBEEK,BELGIUM. FAC UNIV NOTRE DAME PAIX,ANAL RECT NUCL LAB,B-5000 NAMUR,BELGIUM.QUAEYHAEGENS, C, INST MAT RES,DIV MAT PHYS,SCI PK,UNIV CAMPUS,B-3590 DIEPENBEEK,BELGIUM.