Microstructure of the spray formed GCr15 steel was observed by optical microscopy and TEM, shwoing fine pearlite with the interspacing of 85nm in as-sperayed samples and maternsite of the width of 0.35 mum in oil-quenched samples. Two formulae correlating the hardness with the interspacing of the pearlite and the width of the martensite respectively were derived on the basis of the Hall-Petch relation. A comparison of CCT thermograms between the as-sprayed and the as-received GCr15 steel revealed the differences of Ms temperature and transformation temperature from pearlite to austenite, which were quantitatively investigated and found that it originate from different carbide distribution and different carbon content in the matrix of steel.
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