| Abstrakt: |
1.Powder steel R6M5K5-MP, by exceeding the bending strength and impact strenth of normal production steel 10R6M5K5, hields to it in crack propagation resistance (KIC) as a result of a reduced capacity for stress relaxation.2.The danger of premature failure with the presence of different types of defect (nonmetallic inclusions, powder particles of another composition, pores with acute angle edges drawn out along the deformation direction, graduation lines, undercuts, grinding cracks, etc.) is much greater for powder steels than for similar steels of normal production. In view of this the maximum effect of using powder steels may only be obtained with careful observation of preparation technology for blanks and tools made from them.3.Independent of the production method, fracture of the test steels in impact and static loading (including a previously applied stress concentrator) has a typical cleavage nature through the body of grains and interphase (carbide-matrix) surfaces at 20°C, i.e., brittle, but it is ductile at 550°C.4.A further increase in the operating capacity of powder high-speed steels may be achieved with the use of atomization production methods followed by treatment for improving uniformity of the size fractions for powders and the sizes of carbides in compacted blanks. |
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