Surface modification by electron beam glazing

Experiments were conducted with three common steels, namely AISI 1045, AISI 4150 and AISI 1090, using an electron beam as an energy source to provide rapid superficial surface fusion. Beam scanning velocities of 75-2592 cm s-1 were used. Increasing the beam scan rate resulted in an increased hardness for scan rates of up to 1300 cm s-1. This scan rate gives a calculated cooling rate in excess of 107 degCs-1. Microhardness was used as a measure of the performance resulting from the rapid solidification rates obtained. The measured Vickers hardness was converted to and reported as the Rockwell C scale hardness. The fused layer appears as a metastable solid solution with a fine precipitate associated with the overlap of fused paths. The Vickers hardness was found to be significantly harder (1100 HV compared with 700 HV) than that of the same materials treated by a conventional quench. The treated layer also appears to have good fracture toughness in that adjacent and superimposed hardness indentations and those near an edge did not induce cracking. Post-fusion thermal treatments at 200 and 5900C and a complete quench and temper all resulted in a lower measured hardness. (Auth.)