Teppo Fält

Development of Nanostructured Al2O3-Ni HVOF Coatings

HVOF thermal spraying has been developed to deposit dense Al2O3-coatings for improved protective properties. As compared to generally used plasma sprayed coatings HVOF coatings can be prepared much denser and thus are better suited for applications where protective properties of the coating are needed. In this paper we describe the development of HVOF spraying technologies for nanocrystalline Al2O3- and Al2O3-Ni-coatings. The microstructure and the mechanical properties of these novel coatings are reported and compared to a conventionally processed Al2O3-coating.

Improved Mechanical Properties by Nanoreinforced Ceramic Composite HVOF Coatings

Special nanoreinforced ceramic composite coatings were produced. Dense nanostructured alumina and chromia coatings alloyed with various nanofraction elements such as Ni, NiO, ZrO2 and SiC were manufactured by HV2000 HVOF spraying. As a result coatings with nearly 100% improvements relative fracture toughness, were produced.

Process Optimization for Nanostructured HVOF -Sprayed Al2O3-Based Ceramic Coatings

Special mechanical properties have widely been demonstrated with bulk nanocrystalline materials. An increasing effort has been made to transfer such improvements also into thermal sprayed ceramic coatings. This paper focuses on such efforts in alumina-based ceramic coatings. The optimization of process conditions and effect of different process parameters on the mechanical performance of high velocity oxy-fuel (HVOF) sprayed ceramic coatings is discussed.

Mechanical properties of nanocrystalline HVOF coatings

Thermal spraying (TS) is increasingly used to deposit thick wear resistant coatings on machine and equipment parts. Therefore, it is of uttermost importance to know their mechanical properties in order to tailor and optimize the coatings for various applications. Typically properties of the thermal sprayed coatings are inferior as compared to corresponding bulk materials for various reasons. Furthermore, measurement of mechanical properties of coatings is much more tedious and difficult than deriving bulk properties. In this paper, mechanical properties of alumina based nanocrystalline coatings and the measurement techniques developed are reported. A model relating the microstructure of the sprayed coatings and their properties is introduced and discussed.