In this work, tungsten carbide coatings are deposited by low-pressure cold spraying in order to assess the influence of powder compressive strength and binder materials on coating properties. Powder compressive strength was measured with a micro-compression tester, and cobalt and FeCr in different proportions were used as the metal binder. It was found that compressive strength affects coating hardness as well as deposition efficiency and that the optimum value for deposition efficiency is about 200 MPa. The results also indicate that dense coatings can be produced with either binder material, although coatings with an FeCr binder are the hardest.

The application of ceramic die coatings on tool steel dies in the casting industry has been common practice for many decades. The main function of these coatings is to provide a thermal barrier to prevent premature solidification during die filling, and protect the tool steel die from the effects of molten metal during casting with aluminium alloys. Although these coatings provide good insulation they are fragile and require on-going in-situ maintenance by machine operators. These inherent poor qualities makes the die casting process difficult to control and to maintain cast product quality because the solidification pattern and porosity changes and leads to increased cast product rejects. To overcome the limitations a novel die coat has been developed for the light metal casting industry utilising thermal spraying of co-deposited MgZrO 2 and polymer particles. The coating is then thermally treated to reveal a fine network of porosity that has been found by heat transfer coefficient testing to enhance the thermal properties and overall coating durability during casting. This paper describes the porosity control system which was used to tailor the heat transfer coefficient of co-deposited MgZrO 2 and polymer coatings and compare them with the heat transfer coefficient of commercially available die coats. The inherent porosity and the overall coating thickness were found to have a large effect on the heat transfer coefficient. Results of industrial trials are also presented and show that co-deposited MgZrO 2 and polymer coatings provide considerable improvements to productivity and enhanced coating life in Gravity and Low Pressure Die casting of aluminium alloys.

The direct conversion of heat into electric current is still less developed form of energy conversion. Thermoelectric material working in a temperature gradient is able to induce a voltage that can drive a serial resistor. New research activities try to broaden the employment of thermoelectric generators from spacecraft technologies to terrestrial applications. The main problem at the moment is rather the lack of economic production methods, than the low efficiency of conversion. After an overview about the basics of thermoelectrics and possible applications the paper presents the thermal spraying as an alternative processing method with first attempts to realize graded structures. Al-doped and Co-doped FeSi 2 has been consolidated by APS, SPS, VPS and HVOF spraying. The microstructure, phase composition and oxygen input have been investigated and set into relation to thermoelectric properties.

Fine (median size 6 μm and 0.3 μm) cobalt spinel (Co 3 O 4 ) powders were processed suspended in a suitable liquid phase. Suspensions exceeding 50 wt.% solid phase content were successfully injected into an inductively coupled plasma. Spheroidized powders with large particle size (up to 80 μm) were prepared, and cobalt oxide coatings were produced by this novel RF-SPS method. The microstructural features of the coatings can be controlled by parameter optimization similarly to plasma spraying of dry powders. Numerous variations of the physical and chemical conditions of the process were performed in an attempt to overcome the main disadvantage of the process, i.e. the decomposition of the spinel phase to CoO. So far, the spinel phase could be reestablished only by a post-treatment of the deposited coatings with atomic oxygen in the RF plasma.