Residual stresses in components formed by the laser-engineered net shaping (LENS®) process

The residual stress distributions in two laser-engineered net shaping (LENS(R)) samples were mapped by neutron diffraction. The samples took the form of a thin wall and a pillar of square cross-section. Stresses were measured in the three orthogonal symmetry directions of the parts, parallel and perpendicular to the growth direction. Surprisingly, over most of the bulk of the samples the stress was uniaxial and directed along the growth axis, with compression in the centre of the samples and tension at the edges. The magnitudes of the maximum residual stresses were significant fractions (50 and 80 per cent for the thin wall and pillar respectively) of the 0.2 per cent yield point. The origin of the residual stress distributions is discussed qualitatively in terms of the thermal histories of the samples.