APPLICATION OF PULSE-PERIODICAL MODE FOR IMPROVEMENT OF LASER TREATMENT EFFICIENCY

The purpose of the paper is to estimate an application of pulse-periodical mode for improvement of laser treatment efficiency. Laser technologies have been widely used in the processes of material treatment with the purpose to provide them the required surface properties and also for high accuracy cutting of sheet materials. Application of complex treatment is of great interest and especially when it is used for worn-out surfaces with formation of a coating by gas-flame laying of powder mixture of specific composition and subsequent laser fusion.

Increase of laser unit capacity is very important task for higher efficiency of laser technology application in mechanical engineering. Nowadays technological processes using lasers with high average power (more than 100 W) have been applying only sources that are working in two modes, namely: continuous and pulse- periodical (P-P) with pulse repetition rate from some units to several hundred hertz and pulse duration within dozens to hundreds of microseconds and even within milliseconds. On the other hand, in some cases shielding effect of plasma cloud formed during laser alloying, cladding or welding reduces the efficiency of laser treatment up to 50 % depending on plasma composition and laser beam length. High frequency P-P laser systems with high average power working in mode of Q-factor modulation allow to realize principally other mechanism of irradiation interaction with materials that is an ablation. In this case it is possible to provide local energy release both in space and time.

The performed analysis has revealed that P-P mode of laser operation for a majority of treatment processes is much better and more efficient from energetic point of view in comparison with the continuous mode. On the basis of the developments it is possible to make a conclusion that there is a possibility to create laser systems working in high frequency P-P mode with high average power above hundreds watt.

1. Devoino, O. G., Kalinichenko, A. S., Kardapolova, M. A. (2013) Modification of Surface Coatings While Using Laser Heating. Minsk, BNTU (in Russian).

2. Bergmann, H. W., Gundel, P. H., Kalinichenko, A. S. (1988) Laser Surface Alloying of AlSi12 and AlCr2.5Zr2.5 with Transition Metals and Si. OPTO Electronic Magazin, 4 (5), 510-517.

3. Lekala, M. B., Van Der Merwe, J. W, Pityana, S. L. (2012) Laser Surface Alloying of 316L Stainless Steel with Ru and Ni Mixtures International Journal of Corrosion, 2012, Article ID 162425. Doi: 10.1155/2012/162425.

4. Hung-Yi, Chen, Shiuh-Jer Huang (2004) Ti6A14V Laser Alloying Process Control by Using a Self-Organizing Fuzzy Controller. International Journal of Machine Tools and Manufacture, 44 (15), 1653-1665.

5. Devoino, O. G., Kalinichenko, A. S., Kalinichenko, U. A. (2007) Laser Alloying of Al-Si Alloys with Transition Metals. Proceedings of the 5th LANE Conference, Meisenbach Verlag, 761-765.

6. Devoino, O. G. (2013) Control Gradients Properties a Hardening Process of Laser Processing. Luchevye Tekhnologii i Primenenie Lazerov. Trudy VII Mezhdunarodnoi Nauchno- Tekhnicheskoi Konferentsii [Beam Technologies and Laser Application. Proceedings of the 7th International Scientific and Technical Conference]. Saint-Petersburg, Publishing House SpB, SPU, 203-211 (in Russian).

7. Devoino, O. G., Kalinichenko, A. S., Kardapolova, M. A. (2014) Formation of Gradient Surface Layers by Means of Multifold Laser Alloying. Nauka i Tekhnika [Science and Technique], 2, 3-6 (in Russian).

8. Devoino, O. G., Kalinichenko, A. S., Kardapolo- va, M. A. (2006) Methods of the Increase of Wear Resistance of Working Surfaces Applying Laser Treatment. Surface Modification. Proc. Workshop. 21-22.06.2006. Seoul. Korea, 248-251.

9. Kardapolova, M. A. (2012) Formation Wear-Resistant Coatings by Combination of Electrospark Alloying and Laser Treatment. Machine and Industrial Design in Mechanical Engineering - KOD 2012. Proceedings of the 7th International Symposium. Balatonfured, Hungary, 523-526.

10. Devoino, O. G., Kalinichenko, A. S., Kardapolova, M. A. (2011) Laser Treatment of Wear-Resistant Gas- Thermal Composite Coatings. Minsk, BNTU (in Russian).

11. Apollonov, V. V., Kiyko, V. V., Kislov, V. I, Suzdaltsev, A. G., Egorov, A. B. (2003) High-Frequency Repetitively Pulsed Operating Regime in High-Power Wide-Aperture Lasers. Quantum Electronics, 33 (9), 753-757. Doi: 10.1070/QE2003v033n09ABEH002496.

12. Apollonov, V. V. (2010) «Impulsar»: New Application for High Power High Repetition Rate Pulse-Periodic Lasers. Laser Pulse Phenomena and Applications. Croatia, INTECH, 29-44.