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OFIENGINE
Development of the New Thermal Spraying Equipment and Technology for Production of Components for Marine Transport Engines

The improved maintenance and reliability behaviour of two-stroke diesel engines are becoming the key factors for final users and industrial suppliers. The project objectives, therefore, are as follows:

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  • to develop the technology of manufacturing marine engine components with improved technical and service characteristics using novel thermal spraying techniques
  • to develop the new thermal spraying equipment for production of the components for marine transport application.

In order to achieve these objectives, an oxy-fuel ionisation (OFI) installation will be developed that gives the best coating structure and in-service performances but with 1.5-2.0 times reduced process costs in comparison with HVOF spray techniques.

It is intended that the oxy-fuel ionisation technology will be developed up to a prototype unit for marine transport application.

Background

The two-stroke large bore diesel engine is recognised as the most economical and reliable prime mover for the marine fleet with a long running time. Many parts of the diesel engine are being currently critically reviewed with the purpose of increasing their durability and reliability with a minimum of maintenance requirement. The exhaust system is a cost-intensive part of the engine and its operation under extreme load conditions forces the need for engineered materials, maintenance and reconditioning services for these components. Expensive materials are required to endure erosion at high temperatures, pressures and corrosion deposits, Nimonic alloy being the most renowned material for this application but the standard valve spindles are manufactured out of heat-resistant steel with a hard-faced seat area. The cost of these materials, and the need to reduce service intervals, are a significant proportion of the price of an exhaust valve, justifying the need for effective maintenance and reconditioning procedures. The usual procedures involve the welded satellite recharge of valve seats and HVOF application of cermets on to a valve spindle.

Objectives

The purpose of this project is to solve this situation, thus increasing the durability of the exhaust system and the global engine, by the development of a new oxy-fuel ionisation (OFI) thermal spray technology. This is able not only to generate the technically required coatings to fight the identified wear mechanisms but also to compete with the current processes in cost, reliability and industrial affordability.

Summarising, the objectives should be:

  • to increase the durability of critical exhaust components (valve spindles, seats, etc.) and other pieces of two-stroke diesel marine engines by the use of advanced coatings
  • to reduce the cost of manufacturing coated components
  • to increase the number of suppliers offering these services and thus increasing the effective quality of the components used in marine diesel engines
  • to develop the technology of manufacturing marine engine components (valve spindles, valve seats, piston rods, cylinder cover and connecting rods) with improved technical, economic and service characteristics using novel thermal spraying techniques
  • to develop the new thermal spraying equipment for producing the components for marine transport application.
Schematic diagram of the OFI spraying process
Schematic diagram of the OFI spraying process

Description of work

The project’s work is divided into seven technical work packages.

Work Package 1: Specifications: A complete data collection and compilation of the specifications will be performed on the existing practices and desirable product properties.

Work Package 2: Development of the new thermal spraying equipment: The objective is to develop, design and manufacture the prototype oxy-fuel ionisation (OFI) unit.

Work Package 3: Development of OFI coatings and procedures: The coatings will be developed, evaluated and compared to coatings applied by conventional HVOF and HFPD spraying.

Work Package 4: Manufacturing the coated marine engine components: The objective concerns manufacturing and testing the marine engine components.

Work Package 5: Testing of the developed coated marine engine: The objective is integration of the developed marine engine components and testing in the industrial partners’ system.

Work Package 6: Mathematical modelling of thermal spraying process and optimisation: The objective deals with the modelling of a pressurised diffusion flame, which will include the interaction of the high-velocity and high-temperature plasma-flame exiting from the Laval nozzle with the surrounding gas at atmospheric pressure and with the substrate, as well as the kinematic and thermal behaviour of powder particles injected within the jet.

Work Package 7: Dissemination and exploitation of results: The objective is awareness raising and providing information to the main stakeholders, and these are research and expert institutes, industry managers, policy-makers and main environmental and technology associations.

Results

The expected results of OFIENGINE are the following:

  • Reduction (2-3 times) in the maintenance and service requirements for diesel components.
  • Reduction in the process cost of coated components by 50%.
  • Increasing the range of materials deposited starting from low-melting Al and Cu without oxidation to metals, superalloys, carbides and oxides.
  • Increase of the wear-corrosion resistance of valve spindle components.
  • Increase the thermal isolation and corrosion resistance of pistons crowns, valve bottom-heads, etc.
  • New developed equipment made available to the market.
  • Engine components manufactured by the new process made available to the market.

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