Abstract: EPMA mapping analysis method was proposed to determine the depth of decarburization of steels. The determination of the depth of decarburization was completed on three typical steels such as hot rolled 75Cr1 high carbon tool steel, 20CrMnTi quenched gear steel and cold rolled and annealed SH1100 low-carbon carriage plate steel respectively. The results show that for the medium and high carbon steel specimen with pearlite plus ferrite microstructures, the value of depth of decarburization provided by micrographic method is about 77% of that by EPMA mapping analysis method. For the determination of decarburization depth of quenched and tempered steels, the accuracy degree of EPMA mapping analysis is less than 10 μm, which is one tenth of the micro-hardness testing. For low carbon steels which are difficult to determine the depth of decarburization generally, the measurement values of EPMA mapping analysis are accurate considering that the depth of decarburization is determined based on the transition curve of average carbon content over a large zone of the steel specimen. EPMA mapping analysis method deserves to be applied extensively with apparent advantages such as unlimited steel microstructure, loose requirement for sample shape, good data stability, high accuracy and easy to operate, etc.

Key words: electron probe micro-analyzer (EPMA), mapping analysis method, depth of decarburization, steel