Increasing the wear resistance of superficial layers by laser alloying.

Demian, Gabriela ; Demian, Mihai

1. INTRODUCTION

Using high power laser with continuous emission give the possibility to use some heat treatment technology and the results is the improvement of the mechanical and anticorrosive properties of metallic materials. (Steen 1991).

The attitude of the carbon steel at wear and friction is influenced by the structure and chemical composition. The wear is smaller when the steel has a martensitic structure.

After the experimental researches, the martensitic structure of the hardened steels by quenching has a high wear resistance.

To improve wear resistance of the machine components can be use laser technology. Can be use laser technology in order to obtain alloyed layers. The alloyed layer gives to the machine component another mechanical property, in order the hardness has an increase values. The alloyed layer is obtained using metallic powder. (Barton et. al., 1988).

In the future research will be extended on different types of steels with the scope to increase the wear resistance. The increase of the wear resistance will be made by the different kind a thin layers deposition with new physical- chemical techniques as PVD and CVD.

2. MATERIALS AND METHODS

In the first case, the samples are a cylinder 023 mm and a block with the dimension 17x15x12mm.

The cylinder sample (2 C50 - EURONORM 10083-1) is superficial hardened with high power C[O.sub.2] laser in continuous wave. Figure 1 illustrate the microstructure of the hardened layer

Superficial heat treatment with laser was made using a displacement of the sample in the field of the laser radiation.

The results are surface in ring or spiral form with a width approximately equal with diameter of the laser beam 2,4 mm.

To obtain a hardened zone in ring form the sample was rotate with 5mm/s linear speed or 10mm/s. to obtain a hardened zone in helical form, the sample must make a rotation and translation motion.

3. RESULTS AND DISCUSSIONS

After the laser beam passing the microstructure of the base material is changing. The new martensitic microstructure can be seen in fig.1 and fig. 2 (Demian & Demian, 2005).

In the fig. 1 and fig. 2, can be measured the thickness of the heat treated layer and the microhardness.

The results of the tests, show, that the gravimetric wear corresponding to the first stage of the working friction couples and the average friction factors (fig.3). (Demian et. al., 2008).

Figure 3 show the diagrams concerning the progressive wears of each friction couple.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

In the fig 4 can be seen the zone that support the microhardness measurements.

[FIGURE 4 OMITTED]

In the fig. 5 can be seen the microhardness hardened layer to an output of 1200W 2.4-mm spot and two speeds: v = 10mm / s, v = 15mm / s.

[FIGURE 5 OMITTED]

At the laser alloying techniques, in the alloyed layer can be find dispersed carbides.

In the clad layers, there is a dendritic structure where the alloying powder was melted and dissolves in the base material.

At SEM microscope can be seen the dendritic solidified Nickel base solid solution and fine globular carbides.

[FIGURE 6 OMITTED]

A next step for the research is a real case analyzing a mechanical element as a sample.

Will be analyzed in two cases, first, when the surface of the mechanical element is not treated with laser and in the second case there is a laser deposition or a superficial heat treatment with laser. Fig.6 and fig.7 gives information about laser clad layers and there microhardness.

[FIGURE 7 OMITTED]

4. CONCLUSIONS

After the laser surface treatments it was obtained hard and wear resistant superficial layers. Heat treatment with laser can be performed on complex surface and it is a quick method. At the surface at the machine components laser cladding process permit to obtain, a continuous and adherent super alloy layers. The thickness of the alloyed layers, increase with the power of the laser beam.

Can be obtain a high hardness of the layers when the thickness of the method layers are under 0,8 mm. When there is a multiple cladding it is obtained a good geometry and the dilution of the layers is a low degree. The Nickel base super alloy that results after laser cladding processes has a good wear resistance and can be used for the machine components that work in heavy duty.

5. REFERENCES

Bach J, Damascheck R, Geissler E & Bergmann H.W. (1990). Laser transformation hardening of different steels. In: Bergmann HW and Kupfer R, editors. Proceedings of the 3rd European Conference on Laser Treatment of Materials (ECLAT'90), p. 265-282 Coburg, Germany: Sprechsaal Publising Group.

Barton, G., Bergmann, H.W., Mordike, B.L. & Gross, N. (1988). Surface Alloying During Lasermelting, Laser Materials Processing II, SPIE vol.455, pp. 113.

Bergmann H.W., K. Schutte, E. Schubert & A. Emmel. (1995). Laser-surface processing of metals and ceramics for industrial applications, Applied Surface Science, Volume 86, Issues 1-4, p 259-265.

Demian G & Mihai Demian. (2005). C[O.sub.2] Laser Procesing; Proceedings of International Scientific Conference MicroCAD 2005, University of Miskolc pag 19-24, ISBN 962-661-658-2.

Demian G & Mihai Demian. (2002). Theoretical and experimental study of the heat treatment of steel surface using C[O.sub.2] laser, U.P.B. Scientific. Bulletin. Series A, Vol 16, Nr 7682, p. 73-80, ISSN 1223-7027.

Demian G., Mihai Demian, L. Grecu & V. Grecu (2008). Tribological testing on the steel hardening with laser;

Friction, Wear and Wear Protection; ISBN 978-3-527-32366-1 Deutsche Gesellschaft fur Materialkunde e.V., pag 682-690.

Shafirstein G., S. Ariely, M. Bamberger & F. Maisenhalder, M. Langohr. (1994). Mat. Sci. and Tech,, vol. 10, pp. 837-840.

Steen, W.M. (1991). Laser Material processing, Springer Verlag, 266p.