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Ni-W-Si intermetallic composite coatings consisting of primary tungsten dendrites and eutectic W/WSi2 were fabricated on 45 steel by laser cladding process using Ni-W-Si powder. The microstructure and composition of the coatings were characterized by SEM, XRD and EDS. The effect of the W content on the hardness and wear resistance of coatings was investigated. Results indicate that attributed to the high hardness and toughness of tungsten dendrites and fine and compact eutectic W/WSi2, coatings had high hardness being 950HV in maximum and the wear resistance was elevated to 4-8 times higher.

The study of residual stress in engine block has the potential to provide the necessary infrastructure for a wide range of scientific and technological developments concerning the automobile industry. Such study can act as centre of excellence for scientific studies in the field of materials science and machinery as well as for industrial applications. The basic principle of measuring residual stress with grooving method and the main measuring steps were introduced in this paper. Groove cutting in the internal surface of engine block surrounds a given area in which the remaining stress is released, and then the strain results are recorded through strain gauge. The residual stress test data were compared at different positions of each engine block. It is found that engine blocks A and D on the sides of engine develop higher residual stresses than blocks B and C in the centre of engine. The stresses can be higher than 200MPa in tension in engine block A, depending on the geometry, size, microstructure, subsequent welding process, and cutting sequence. In addition, residual stress at the bottom of engine is higher than that at the top because of the structure of the engine. The residual stress is also calculated by numerical modeling method from which it shown that the condition is commendably fit the results which the distribution of stress.

The tension, Charpy notch impact and fracture toughness tests on structural steels Q235B and Q345 were carried out under different prestrains. Ductile to brittle transition curves are investigated using Charpy impact tests. The results indicate that the prestrain decreases the impact toughness of both base metal (BM) and weld metal (WM); and increases the ductile-brittle transition temperature as well as the risk of fracture. The prestrain is also found to have a more significant effect in a less ductile material. River marking, the characteristic of cleavage fracture, is observed in the Q235B WM specimens 10% prestrain conditions at 0°C. The fracture surfaces of Q345 WM specimens are characterized by dimple-like structures. The depth of these dimples is decreased under prestrain applied before welding. The CTOD-prestrain curves are obtained using Boltzmann relation.

In this paper, the influence of double wire submerged arc welding parameters on the mechanical properties of high strength low alloy has been investigated. The 20mm steel plate has been welded by double wire submerged arc welding process using different welding parameters. The Charpy absorbed energy of specimens is assessed using impact test at the temperature of -50°C. Testing results show that high heat input parameters will lead to low strength of welded joint. Impact toughness of fusion line is lower than that of other areas of welded joint.