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Topic: FP7-SME-2012-BSG Research for the benefit of SMEs

Title: BRAZEHARD_WEAR PROTECTION BY HARDFACING BY BRAZING

Subject of the project:
Development of an innovative wear resistant composite coating based on mixing an iron base brazing filler metal of low fusion temperature with hard microparticles.

Description of the project:
Ceramic industry experiences high economic losses due to wear-out of critical components exposed to extreme work conditions. Among all elements that suffer major wear-out are the parts of extrusion molds including dies, extruder heads, strainer plates, etc. These components are responsible for providing the final shape of the products as bricks in several shapes and geometries used in the construction industry. In Galicia alone, an estimated 10 M € of losses are made in the ceramic industry due to this phenomena.

The strong degree of abrasion is the main cause of wear-out in these types of extrusion parts. The raw materials used to obtain the ceramic products contain an elevated amount of abrasive elements, including quartz and feldspars. Alloys with a strong degree of hardness are used to improve resistance to abrasion and therefore extend the life-cycle of the molds. At present, tool steels and tungsten carbide materials are being used in the molds. In the case of suffering wear-out, molds are repaired by a welding process, for instance FCAW, MIG/MAG or through Laser processing. In addition, coatings are applied to improve resistance to abrasion.

Nevertheless, these above mentioned processes have a number of shortcomings, originating from the elevated temperatures used during this processes. An undesirable dilution process takes place during the fusion on the surface of the base material. Furthermore, the elevated temperatures that are used during the deposition technique generate residual stresses and distortions within the material, stemming from the fast cooling of the treated parts and the non-uniformity of the temperature field of the treated zone. Another issue is the high surface roughness that remain after the treatment and that prevents the raw material flowing easily within the extrusion process.

Today, molds have despite of the technological advances that have been made in the last years, an unacceptable short life-cycle that result in high maintenance and components costs. Current studies focus on the application of brazing technologies for the deposition of hard coatings. The idea of this process is to use a metallic matrix of nickel base of low fusion temperature (binding alloy). This binding alloy is mixed with hard microparticles with the objective to reinforce the coating and hence, improve wear-out properties by an estimated 20%. In addition, these coatings improve corrosion resistance due to its high content in chrome. High vacuum furnaces are used to apply these hardfacing by brazing. Strong metallurgical bondings are formed between the base material and the hard layer, as well as between the binding alloy and the hard-phase, respectively, as a result of mutual diffusion of the alloying elements. This process has several advantages compared to existing surface alloying methods. Excellent resistance of the coating, surface finish (similar to the one of casting), the possibility of realizing coatings for difficult geometries, are among the advantages that need to be emphasized. Furthermore the brazing process has the advantage of being a simple technology and therefore low cost.

As mentioned above, current developments of the coating by brazing process is centred on the application of nickel based filler metals. Nevertheless, applying nickel increases the cost of the coating. Hence, the challenge is to develop a new low cost alloy with a low melting point able to substitute the expensive nickel.

The objective of this proposal is to study, develop and manufacture new highly wear resistant coatings. These brazing coatings should have low coefficients of friction and low wear-out. The targeted sector is the ceramic industry, resulting in a positive impact for the construction industry. Applications include components that suffer high wear-out, especially molds used in the extrusion process. Successful completion of the project would provide the ceramic industry a new low cost surface technology, thus improving competitiveness. The construction industry benefits from the availability of cheaper ceramic products of added value, as new shapes might be developed. Results will be implemented in the participating SMEs and protected. Furthermore, results will be presented in congresses and workshops under the supervision of the participating SMEs.

Partners sought and role in the project:

SME:
END user of the new wear resistant coating _ We are looking for a ceramic company (SME) specializing in the manufacture of structural ceramics like bricks and tiles by extrusion process, which shows abrasive wear problems in different elements, dies, molds, nozzles, etc.

Contacto:

Enrique Machuca García
Tel.+34 955 40 55 78 – Fax. +34 955 03 98 35
e-mail: enrique.machuca@juntadeandalucia.es