Heat treatment of high-speed steel with continuous laser
When preliminarily hardened high speed steel, tempered at 350–560°C, is treated by a continuous CO2-laser with energy density J=34±3 MJ/m2, a strengthened layer with maximal thickness and hardness forms.
Accelerated heating by laser beam to temperatures in the range between Ac3 and Tpl and practically instantaneous cooling to normal temperature at rates of more than 104°C/sec give rise to a highly disperse (in melting) and fine-grained structure recrystallized by precipitation hardening (in quenching in the solid state) and consisting of martensite, residual austenite (in increased amount), and carbides (in a small amount). The intense dissolution of ledeburitic carbides type M6C in the laser-hardened zone causes additional alloying of the solid solution, increased stability of the residual austenite, and super-sautration of the finely accular martensite.
The decomposition of residual austenite and the intense dispersion hardening in the process of tempering at 560–600°C 1 h increase the hardness of the laser-hardened layer of high speed steel R6M5 by 2–4 HRCe, and resistance to tempering by 40–50°C compared with conventional heat treatment. The absence of coarse carbide particles in the hardened layer reduced the probability of brittle failure by chipping in operation of the cutting tool.
KeywordsCarbide Martensite Precipitation Hardening High Speed Steel Residual Austenite
Unable to display preview. Download preview PDF.
- 1.P. R. Strutt, "Microstructural refinement of hard iron base materials by laser and electron beam surface melting," Metals Forum,4, No. 1/2, 117–123 (1981).Google Scholar
- 2.B. G. Lewis, D. A. Gilber, and P. R. Strutt, in: Laser and Electron Beam Processing of Materials, Academic Press (1980), p. 747.Google Scholar
- 3.L. E. Greenwald, E. M. Bkeinen, and B. H. Kear, "Laser-solid interactions and laser processing," in: Am. Inst. Phys. Conf. Proc., Vol. 50 (1979), p. 189.Google Scholar
- 4.N. A. Ol'shanskii, A. V. Mikhailov, V. A. Krivonogov, and I. I. Trusova, "Extending the life of alloy steels by electron beam melting of their surface," Metalloved. Term. Obrab. Met., No. 9, 30–31 (1984).Google Scholar
- 5.A. N. Safonov, A. G. Grigor'yants, V. M. Tarasenko, L. G. Ovcharova, and A. F. Baskakov, "Investigation of the structure of steels in hardening and alloying of the surface by continuous lasers," Izv. Vyssh. Uchebn. Zaved., Mashionstr., No. 5, 94–98 (1984).Google Scholar
- 6.D. M. Gureev, V. A. Katulin, G. N. Mirishin, et al., "Experimental investigation of laser hardening of tool steels," Poverkhnost'. Fiz. Khim. Mekh., No. 3, 143–148 (1983).Google Scholar
- 7.V. S. D'yachenko, G. N. Tverdokhlebov, and A. A. Korosteleva, "Special features of laser heat treatment of high speed steel tools," Metalloved. Term. Obrab. Met., No. 9, 25–28 (1984).Google Scholar
- 8.T. I. Lutsenko, "Laser hardening of tools," Metalloved. Term. Obrab. Met., No. 9, 31–33 (1982).Google Scholar
- 9.O. V. Vladimirova, "Hardening the working surfaces of parts and of highly accurate measuring tools with the aid of a CO2-laser," Metalloved. Term. Obrab. Met., No. 5, 17–18 (1983).Google Scholar
- 10.V. A. Burakov and S. S. Fedosienko, "Formation of structures with increased wear resistance by laser-hardening of metal cutting tools," Metalloved. Term. Obrab. Met., No. 5, 16–17 (1983).Google Scholar
- 11.V. S. D'yachenko, "Special features of the structure and the properties of high speed steels after laser treatment," Metalloved. Term. Obrab. Met., No. 8, 50–54 (1985).Google Scholar
- 12.V. S. Kovalenko, in: Treatment of Materials with Pulsed Laser Radiation [in Russian], Naukova Dumka, Kiev (1977), pp. 23–27.Google Scholar
- 13.V. A. Burakov and G. I. Brover, "The effect of laser hardening on the wear resistance of steel R6M5," in: Progressive Methods of Thermal Hardening in Tractor and Agricultural Machinery Construction, RISKhM, Rostov-on-Don (1983), pp. 28–35.Google Scholar
- 14.V. S. D'yachenko and G. N. Tverdokhlebov, "Morphology of the white zones forming in high speed steels after laser treatment," Fiz. Khim. Mekh. Mater.,20, 10–13 (1984).Google Scholar
- 15.L. Ahman, "Microstructure and its effect on toughness and wear resistance of laser surface melted and post heat-treated-high speed steel," Metall. Trans.,15A, No. 10, 1829 (1984).Google Scholar
- 16.I. Artinger, in: Tool Steels and Their Heat Treatment (Handbook) [in Russian], Metallurgiya, Moscow (1982), p. 74.Google Scholar