Electron beam selective melting (EBSM) is a new type of rapid manufacturing of direct metal fabrication technology, which combines electron beam machining with rapid prototyping. It makes use of some advantages of an electron beam, such as high energy density, high absorption rate, and vacuum environment. In this study, direct metal part forming of gas and water-atomized 316L stainless steel powder were researched in detail. The one-dimensional experiments showed that the gas-atomized 316L stainless steel powder could be formed in a solid line at slow scanning velocity and low beam current while the water-atomized powder had serious balling and break-up phenomena at most conditions. The powder mixture containing 40-60 wt % of the gas-atomized powder has the optimum forming ability. The forming technology of the mixture powder must be divided into three steps: placing step, heating step, and melting step. After research on the technology parameters, some two-dimensional facets and three-dimensional parts were produced by EBSM. The microstructure of the three-dimensional forming parts was fine; the interfaces between the layers were metallurgically bonded.

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Hot compression tests are conducted in the present paper to investigate hot deformation behaviour of the newly developed heat resistant steel P92, which is used to fabricate main steam pipes for ultra supercritical power plants. Stress–strain curves at elevated temperatures and different strain rates are obtained. It is found that dynamic recrystallisation happens only when the temperature is above 1100°C and strain rate is below 0·1 s−1. Otherwise, dynamic recovery is the main softening mechanism. Constitutive modelling with the hyperbolic sine, including an Arrhenius term, is used to predict peak and saturated stresses. Material constants for this model are determined. Results show that the model can be used to predict peak and saturated stresses. However, the model would fail in predicting flow stress with respect to strain; thus, a model containing nine independent parameters and the complete form of Spittel equation are utilised to predict flow stress curves softened by dynamic recrystallisation and dynamic recovery respectively since there are no unified equations. The predicted stress–strain curves are in good agreement with experimental results, which confirmed that the models developed in the present paper are effective and accurate for P92 steel.

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Electron beam selective melting (EBSM) is a new kind of direct metal rapid manufacturing technology, which can be regarded as the integration of electron beam manufacturing and rapid prototyping technologies. Because the electron beam has great impact on the powder and the requirement of full density and high melting point needed during the EBSM process, the modified scanning mode of the filling lines in EBSM is achieved by combining the split scanning mode and the rotated scanning mode with the zigzag scanning mode. Meanwhile, the three steps and three portion scanning strategy of the subzones are also derived by the finite element analysis of heat transfer in EBSM. Based on the study of the scanning method of filling lines, some parts of 316L stainless steel powder are manufactured.