European Commission logo
polski polski
CORDIS - Wyniki badań wspieranych przez UE

Development of simple and reliable on-line monitoring equipment for thermal spraying control (DESIRE)

Final Report Summary - DESIRE (Development of simple and reliable on-line monitoring equipment for thermal spraying control)

The DESIRE project was focused on the development of a flame properties monitoring device including hardware and software. Using this new equipment the high quality coating would be guaranteed from the beginning till the end of the spray process.

The development of the equipment proposed in this project offers the possibility to monitor permanently the characteristics of the thermal spray flame, as direct indicator of the stability of the spray process. Thus the promised quality of the sprayed coating could be guaranteed.

Different sprayshops using the same thermal spraying guns, same powders and same parameters produce coatings with different quality. It means that many changes can occur and are not detectable. As a result different coatings and different properties are obtained. The 'in situ' measurement of the flame properties and changes is the only suitable method to guarantee a constant control process, and to assure fulfilment of the strictest demands of the end-users.

Existing equipments are based on expensive measurements of the in-flight velocities and temperatures of individual particles. These equipments are mainly used in research and development centres to correlate the properties of the particles and the characteristics of the coatings. The data obtained by existing equipments should be processed and an expert is needed to correlate these data with the quality of the coating. The monitoring equipments it will be specially developed for small and medium-sized enterprise (SME) needs, since it is not focused on the physics of the process but on the process reproducibility, and does not need the presence of an expert to analyse the data.

By using the new monitoring and control systems the SMEs will guarantee a more stable process control assuring a deeper knowledge of the process progress. The utilisation of the device should improve the quality of the sprayed products, it gives information about process instabilities and possible coating defects and the test coupons can be reduced if monitoring device is used as a process setting procedure. All these advantages should lead to important cost savings but also to important marketing and selling arguments.

The existing equipments are so complex that several days of training are required to understand the 'meaning' of the obtained data. Most of SMEs cannot afford this 'extra time' and finally they refuse to add these equipments to their sprayshops. The new proposed equipment is specially designed for small sprayshops, in order to assure it will be directly introduced into production lines. The developed equipment can be in a short term offered to the market. The equipment is easy to use and can be easily adapted to the existing guns.

The project was divided in five technical work packages (WPs), as follows:

WP 1: Specifications
After defining the needs of the sprayshops and focusing on HVOF technology and the usual coating powders, a general document of specifications was agreed by all the partners. This document was the basis for future development of the monitoring equipment.
A characterisation of the selected coating powder and technology by each spraying partner was performed on produced set of specimens as coating quality reference values.

WP 2. Design and development of the monitoring equipment
Based on the former WP results the monitoring equipment was designed and manufactured. The monitoring system is composed of a sensor head (camera, filtering set) enclosed in an air cooled structure with a window to face the spraying flame which is protected by an air curtain from the dust and particles inherent to the spraying process. The sensor system is connected to a PC control unit with specifically developed software.
The monitoring system has a temperature measurement system to monitor operating condition inside and outside the enclosure to assure system safe operation.
Once the prototype was manufactured laboratory tests were performed to test equipment operability and evolution hardware and software and to adjust sensitivity and operation modes.

WP 3. Adaptability to the spraying equipment
The monitoring equipment was tested at every spraying partner facilities with their specific HVOF gun and coating powder and process parameters.
The equipment worked properly in all the guns where it was installed. It was very easy to be mounted and provided quick useful information about the process variations and control. The equipment was easily adaptable and the monitoring results can be sated as reproducible.
A set of specimens was produced in each sprayshop ranging process parameters from the standard optimal conditions to extreme non usual coating failing conditions with the aim of relating process parameters values with coating quality characteristics by means of monitored flame parameter values. These big amounts of specimens were characterised in terms of coating quality evaluation.

WP 4. Industrial validation
Real tests with industrial parts were also produced at each spraying partner facilities. The monitoring prototype behaved adequately and no operating problem arose. Process flow variations were also induced with the aim of, after metallographic characterisation, carrying out an analysis of the monitoring parameters in relation to coating quality values.
The monitoring device was intended to detect changes in the flame that can advice of a possible coating quality variation with values out of specifications. Taking into account the acceptable coating quality values specified for each spraying process the analysis of the measurements obtained from the tests was performed but it was found impossible to relate the process parameters with the coating quality and consequently with the measured flame parameter values registered by the prototype.
During the tests performed at the spraying companies’ facilities, the aim of the device has been verified in a real manner. Problems with feed flows stability, leaks in the ducts, wear of components, flame shape variations, subsonic flows, feed control instability, etc. have been detected during spraying operations and modified with the operator. The device has shown an ability to diagnose the state or condition of the equipment or process with a glance on the flame screen.

WP 5. Cost analysis
A cost evaluation of the monitoring prototype was performed. The analysis was focused on the manufacturing and assembly costs. Cost of manufacturing and assembly the developed monitoring equipment is low in comparison with the complex devices in the market devoted to research and development. The objective of reducing costs to the 60% of the prices of the equipments in the market has been totally fulfilled.
Benefits achieved by the SMEs are very difficult to estimate due to the few operating hours employed in the prototype validation. The operation of the prototype has not, in these first utilisations, shifted the usual sprayshops process adjustment procedures, making very difficult the estimation of the reduction in time and material when using and trusting the monitoring prototype.

WP 6. Dissemination and exploitation of the knowledge
Dissemination and exploitation activities have been also designed during the very last period of the year. Due to the late launch of the final results and prototype, there has not been time to develop any exploitation or disseminating activity but meetings and communications have taken place with this objective. A detailed plan has been elaborated and designed for future activities.