Microstructure and continuous cooling transformation thermograms of spray formed GCr15 steel

Microstructure of the spray formed GCr15 steel was observed by optical microscopy and transmission electron microscopy, showing fine pearlite with the interspacing of 85 nm in as-sprayed samples and martensite of the width of 0.35 μm 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 continuous cooling transformation 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 originated from different carbide distribution and different carbon content in the matrix of steel.