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Abstract
The conclusions obtained from this investigation are as follows:
1. Good wear resistance and flexural strength can be achieved in chromium-molybdenum cast iron with the composition 12Cr 1Mo 2C due to the presence of martensitic matrix contained in a carbide network.
2. Molybdenum has a marked effect on improving the hardenability of chromium cast irons. Alloys with 1 to 3% Mo can be full hardened by air cooling and produce a full martensitic matrix by air cooling, but one of them with no molybdenum addition can not be hardened by air cooling and the pearlitic matrix was obtained.
3. Molybdenum additions to wear resistant Hadfield manganese steel revealed large improvements of toughness and flexural strength even without heat treatment (50 mm thickness).
4. More increase in molybdenum content did not reveal any increase in flexural strength and wear resistance for both as-cast and heat treated conditions.
5. Introducing ductile reinforcements into chromium-molybdenum white cast iron (50 mm thickness) revealed an improvement in flexural strength when partial fusion of these reinforcements was insured.
6. Heat treatment is essential for all abrasion resistant alloys to improve their wear resistance and flexural strength.
7. The matrix type plays an important role in determining the abrasive wear resistance of chromium-molybdenum alloyed cast irons. Martensitic matrix structure is more resistant than the austenitic one and both of them are much more resistant than the pearlitic structure.
8. Subcritical (tempering) heat treatment after air hardening of the investigated alloys at 500 oC resulted in marked improvements for both the hardness and abrasion resistance, but these properties deteriorated significantly at higher tempering temperatures.
9. The differing responses of the alloys to subcritical heat treatment at 500 oC could be related to the molybdenum additions. Secondary hardening may be occurred at this temperature for alloys with 3% Mo content, but one of them with 1% Mo content did not show the effects of secondary hardening.
10. No significant changes could be detected in the microstructure of the alloys after subcritical heat treatment at 500 oC following the hardening heat treatment by an optical microscope.
11. The results of hardness measurements can be used to assess wear resistance of the investigated alloys.