Andrew Siao Ming Ang

Thermal Spray Maps: Material Genomics of Processing Technologies

There is currently no method whereby material properties of thermal spray coatings may be predicted from fundamental processing inputs such as temperature-velocity correlations. The first step in such an important understanding would involve establishing a foundation that consolidates the thermal spray literature so that known relationships could be documented and any trends identified. This paper presents a method to classify and reorder thermal spray data so that relationships and correlations between competing processes and materials can be identified. Extensive data mining of published experimental work was performed to create thermal spray property-performance maps, known as “TS maps” in this work. Six TS maps will be presented. The maps are based on coating characteristics of major importance; i.e., porosity, microhardness, adhesion strength, and the elastic modulus of thermal spray coatings.

Manufacturing of nickel based cermet coatings by the HVOF process

Advanced particle diagnostic technology has been applied to establish process parameters to deposit high quality nickel based carbide cermet coatings for marine hydraulic applications. The cermet coatings are produced via the kerosene fuelled high velocity oxygen fuel (HVOF) spray process, which uses a hypersonic flame jet to melt and accelerate feedstock particles onto the component surfaces. The traditional ‘trial and error’ procedure is not technically robust, as well as being costly and time consuming. Instead, a superior method is implemented in the current study that performs real time monitoring of the process parameters associated with the HVOF flame jets. Subsequently, coatings can be produced with the knowledge of the inflight particle size, temperature and velocity profiles. The analytical results allow identification of suitable coating process parameters, which translate to coatings of lower porosity and enhanced mechanical performance.

Development of processing windows for HVOF carbide-based coatings

Optimized processing windows for spraying high-quality metal carbide-based coatings are developed using particle diagnostic technology. The cermet coatings were produced via the high-velocity oxygen fuel (HVOF) spray process and are proposed for service applications such as marine hydraulics. The traditional “trial and error” method for developing coating process parameters is not technically robust, as well as being costly and time consuming. Instead, this contribution investigated the use of real-time monitoring of parameters associated with the HVOF flame jets and particles using in-flight particle diagnostics. Subsequently, coatings can be produced with knowledge concerning the molten particle size, temperature, and velocity profile. The analytical results allow identification of optimized coating process windows, which translate to coatings of lower porosity and improved mechanical performance.

A comparison of the antifouling performance of air plasma spray (APS) ceramic and high velocity oxygen fuel (HVOF) coatings for use in marine hydraulic applications

Abstract Maritime hydraulic components are often exposed to harsh environmental conditions which can lead to accelerated deterioration, reduced function, equipment failure and costly repair. Two leading causes of maritime hydraulic failure are biofouling accumulation and corrosion. This study examined the antifouling performance of three candidate replacement high velocity oxygen fuel (HVOF) coatings relative to the performance of the current baseline air plasma spray (APS) ceramic coating for protection of hydraulic actuators. Following 20 weeks immersion at tropical and temperate field exposure sites, the control APS ceramic accumulated significantly greater levels of biofouling compared to the HVOF coatings. More specifically, the magnitude of growth of real-world nuisance hard fouling observed on in-service hydraulic components (eg calcareous tubeworms and encrusting bryozoans) was significantly greater on the APS ceramic relative to HVOF coatings. Possible explanations for the observed patterns include differences in surface topography and roughness, the electrochemical potential of the surfaces and the colour/brightness of the coatings.