In the last 15 years, the cold spray process has demonstrated a great efficiency for the deposition of metallic powders. In this case, the consolidation of coatings is achieved thanks to the high kinetic energy of unmelted particles exhibiting a ductile behaviour. Dealing with ceramics, cold spray is also of great interest because one can expect properties not reachable with classical thermal spray technologies thanks to lower involved temperatures. However, cold spray of ceramics still remains challenging because of the ceramics intrinsic brittleness. Here, in the specific case of hydroxyapatite and to overcome this brittleness issue, we investigate the role of an intermediate PEEK layer between the substrate and the deposit. We highlight how this sublayer previously deposited by FS or air APS spraying can help improving the consolidation of the coating and its growth.

The aim of this work is to evaluate the brittleness of suspension sprayed aluminum oxide coatings with various methods, including Vickers indentation fracture toughness, four-point bending, and high-velocity particle impact testing. Coatings were applied via high-velocity suspension flame spraying (HVSFS) using suspensions of isopropanol and water solvents. HVOF-sprayed Al 2 O 3 powder feedstock was used as a reference. The tests are described and the results are presented and discussed.

Iron based coatings have recently gained much attention as they have favorable mechanical, frictional, and corrosion properties. The coatings possessed a high content of iron borides are particularly valuable for satisfying engineering needs. Boron and iron form two major boride phases, FeB and Fe2B, with different mechanical and thermal properties. Orthorhombic boride FeB is considered to be viable candidate to enhance the surface hardness and wear resistance of components, since it has high hardness. Producing of such coating by cold spray method is considered to be an alternative for boronizing method which is a conventional thermochemical surface hardening process. In this work, the crushed ferroboron (FeB) powders of Fe-17.9B-0.4C-1.6Si-0.3Al (wt. %) were deposited onto low carbon steel substrate by cold spraying. However, low and high pressure cold spraying allowed depositing very thin and single layer on the substrate, due to the intrinsic brittleness of the powder. Therefore, several contents of Al, Ni and Fe metallic powder and their combinations were added to FeB powder to obtain thick coating via cold spray processes. Post heat treated coatings at a temperature of 700 °C resulted in increase of the hardness, possibly the formation of hard phases such as intermetallic compound.

The brittleness of intermetallic compounds severely hampers their appliance in industry as high temperature structural materials. In order to make use of their good qualities and avoid the influence of their disadvantages, this paper put forward another method on the application of intermetallic compounds--using as coatings on the surface of structural materials. Lots of experiments have been done on Fe-Cr-Al intermetallic compounds and excellent coatings were acquired by high temperature in-situ reaction process. The coating is compact and bonded well with substrate. And the result of experiment shows that it has wonderful corrosion resistance to molten zinc.

Thermal plasma CVD is hoped to be made fit for practical use because this process is the process which can fabricate precisely structure and component controlled coatings. Especially, TPCVD will be used in the industrial fields where thermal spraying has been used so far since TPCVD come to be studied under an atmospheric environment recently. However, TPCVD coatings fabricated under an atmospheric environment is porous and brittle. So that, TPCVD has been mostly carried out under a low pressure environment and high equipment cost has been demanded. As for the method to solve this problem, according to the report on a gas-deposition process, improvement of the jet flow is thought to be useful. Therefore, in this study, in order to obtain dense and rigid film by TPCVD under an atmospheric environment, Dense oxide coating deposition by High velocity TPCVD utilizing boiling of metal alkoxide was carried out. Consequently, though only brittle coating was deposited on the condition without boiling of metal alkoxide, dense and rigid coating was deposited even under an atmospheric environment on the condition with boiling. From this result, TPCVD was found to have high potential for rapid deposition of dense and rigid coatings.

Quasicrystalline phases improve many alloy properties such as thermomechanical stability, thermal and electrical conductivity, and tribological performance. High hardness, however, is accompanied by brittleness, an undesired property in many applications. Reduced brittleness can be achieved by embedding quasicrystalline phases in a more ductile material, forming a metal-matrix composite that retains some quasicrystalline properties. This study evaluates thermally sprayed coatings made from different compositions of such composites. The coatings assessed were produced by arc-wire, HVOF, and atmospheric plasma spraying using various forms of feed material, including blended, agglomerated, chemical encased, and attrition-milled powders and filled wires. The investigation involved metallurgical analysis, proving the existence of quasicrystal content and assessing the matrix phase, and tests showing how sliding wear is influenced by the composition of quasicrystalline phases.