The need for better performing and lower weight coating materials has almost constantly pushed the development of a technology making possible spraying materials like SiC. NTNU made it possible to spray SiC by coating each SiC particle with a protective oxide layer of yttrium aluminium garnet (YAG) acting as a matrix. YAG prevented SiC from decomposing at temperatures above 2500 C, which are easily reached during thermal spray. Seram Coatings commercialises this invention under the name of ThermaSiC since 2014. ThermaSiC is under qualification in many different branches (steel and glass production, microelectronics, oil and gas, etc) with different customers. However, if the same product is developed with a metal matrix, new thermally sprayed coatings would emerge for a whole new range of applications.
Introducing a metal matrix opens new market possibilities such as those in need of low weight ductility, erosion resistance, thermal/electrical conductivity and wet corrosion resistance, but also the more recent and in high demand cathode materials for fuel cells. A typical example is the widely used WC-Co(Cr) feedstock material, which covers most of the thermal spray cermet market. The main drawback is that tungsten carbide (WC) cannot withstand aggressive chemical environments and temperatures higher than 500 C. Therefore, SiC has been sought for a long time in thermal spray due to its excellent chemical resistance, thermal conductivity, coefficient of thermal expansion, electrical conductivity, etc. Seram Coatings successfully developed a metal bound SiC composite feedstock material at lab scale in 2016 that was filed for patent in 2017. PilotSiC project will validate a prototype reactor design to achieve a pilot production of metal bound SiC powder to qualify the product with customers. The successful realisation of this project will represent a big step for Seram Coatings as a scale-up company, by opening a new pilot production line for a second product.
This project has been set up with the aim at solving a very relevant industrial problem for the thermal spray market (i.e. coating industry): the production of a ceramic-metallic feedstock material for thermal spray containing silicon carbide (SiC). This is a very challenging process because SiC has very low wettability with most engineering (transition) metals such as iron, nickel, cobalt, chromium, and their alloys. A larger part of the thermal spray market needs feedstock materials consisting of ceramic particles with metal binders in order to bring ductility, toughness, erosion resistance, and corrosion resistance. A great example is the widely used WC-Co(Cr) feedstock material for thermal spray. This material takes most of the thermal spray ceramic-metallic coatings market and it is present in many applications were toughness is required due to complex geometries, bending movements and harsh chemical environments (e.g. aerospace, automotive, civil infrastructures, machinery, etc). The main drawback of these coatings are that tungsten carbide (WC) cannot withstand most aggressive chemical environments, temperatures higher than 500 C, wear of diamond like materials, etc. Also the raw materials used in WC-based coatings originate in many cases from doubtful sources with respect to ethical practices in industry. Therefore, SiC has been sought for a long time due to its excellent chemical resistance, thermal conductivity, coefficient of thermal expansion, electrical conductivity, etc, and also due to its more ethical production sources. These properties are currently lacking in the current ceramic-metallic thermal spray materials and would be necessary to cover in order to improve the efficiency and performance of many engineering components. At Seram Coatings we are developing a prototype reactor capable to produce metal-bound SiC powder for thermal spray. This unique reactor is in the development phase and needs piloting and testing to reach the commercial phase.