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Effect of Gamma and Beta Rays on Surface Hardening in High-Speed Steel

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 احمد محمود عبد اللطيف الخفاجي 6/10/2011 4:29:35 PM
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               Introduction Hardness is the most important property which determine the use of steel in specific industry applications and tools, so it is still a subject of interest. Lin [1] has studied the effect of titanium content on the hardening behaviour of medium carbon steel alloyed with chromium and molybdenum. He found that the optimum titanium content for superhardening is between 0.03-0.05 wt%. Pan  et al. [2] have investigated the effects of silicon additions up to 3.5 wt% on the mechanical properties of high speed steels. They showed that silicon additions can increase the temper hardness of steels Fe-16 Mo-0.9C, 6W3Mo2Cr4V and W3Mo2Cr4V, but yield an opposite influence on the temper hardness in W9Mo3Cr4V steel. Dimitrov et al. [3] have studied the effect of high speed electron beam on the hardness of conventional ion nitriding steel with nominal composition (wt%) of 0.42% C, 0.96% Cr, 0.6% Mn, 0.37% Si balance Fe. They found that the hardness of the electron beam hardened layers varies in the range 800-850 HV. Park et al. [4] have investigated the effect of alloying elements on the hardness of four high-speed steel. De Andres et al. [5] have investigated the effect of carbide-forming elements on the response to thermal treatment of the X45Cr13 martensitic stainless steel. Robertson et al.[6] have found that the hardness as measured on the ion-irradiated zone of 316L stainless steel is modified by postirradiation thermal annealing and that the amplitude of this modification is important at 600 degrees C. Choo et al. [7] have found that high-energy electron beam irradiation can be effectively applied to the surface hardening process of an AISI steel used for automotive crankshaft. In the present work, the effects of gamma and beta rays on the surface hardness of high-speed steel have been investigated.           Experimental  In order to investigate the influence of gamma and beta rays on the surface hardness in high speed steel, two identical sets of hardened drills were prepared. Set No.(I) contains 8 samples, each of them was irradiated with gamma rays emitted from Co60 source for times range between 24-580 hr. The Co60 source emits two characteristic energies of 1.17 MeV and 1.33 MeV, the source activity was 200 Ci, and the distance between the source and the irradiated sample was 10 cm. Set No.(II) also contains 8 identical samples of hardened drills. They were subjected to beta rays irradiation for times ranging from 24 hr to 624 hr. The beta source was Sr90 with a maximum energy of 2.3 MeV and an activity of 250 mCi. The distance between the source and sample was 4 cm.Two identical sets of unhardened steel disks were also prepared to be irradiated with gamma and beta rays. Set No.(III) of unhardened disks were subjected to gamma irradiation with the same conditions of set No.(I). Whereas set No.(IV) of samples were irradiated with beta rays with conditions similar to those of set No.(II). The time intervals of irradiation for set No.(III) and set No.(IV) were 26-720 hr and 26-672 hr respectively. For each set of samples, the hardness was measured before and after the irradiation process.

  • وصف الــ Tags لهذا الموضوع
  • hardening; high-speed steel; irradiation

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