This paper presents in-time motion adjustment in laser cladding manufacturing process as a means to improve dimensional accuracy and surface (nish of the built part. Defects occurring during laser cladding degrade the part quality such as dimensional accuracy and surface (nish. In this paper, in-time motion adjustment strategy was presented to remedy and eliminate defects occurring during laser cladding to improve the dimensional accuracy and surface (nish. Based on the relationship between the motion of laser head relative to the growing part and other parameters in e4ects on clad pro(le, the laser traverse speed, stand-o4 distance and laser approach orientation to the existing clad layer were adjusted by instructions from a close-loop control system in real time to remedy and eliminate defects. The results of the experiments veri(ed the e4ects of in-time motion adjustment on dimensional accuracy and surface (nish.

In this paper, model of effects of powder concentration distribution on fabrication of thin-wall parts in coaxial laser cladding was developed. There exists relationship between powder concentration distribution and power density distribution, which affects fabrication of thin-wall parts in coaxial laser cladding. Changes in powder concentration distribution lead to changes in wall thickness and wall growing rate. Fluctuation of powder feed rate deteriorates the growing wall in laser cladding. Deviation of the powder flow stream makes the powder concentration distribution, the thermal flux density and consequently the molten pool not symmetrical against the x-axis, resulting in irregular upper faces of the formedwall. This was verifiedby the results of experiment.

In this paper, a model of cross-section clad profile on the substrate in coaxial single-pass cladding with a low-power laser was studied. The static model of powder mass concentration distribution at cold-stream conditions was defined as a Gaussian function. In coaxial single-pass cladding with a low-power laser, since the influence of surface tension, gravity and gas flow on the clad bead could be neglected, the cross-section profile of the clad bead deposited by a low-power laser on the substrate was dominated by the powder concentration at each point on the pool and the time when the material was liquid at this point. The height of each point on the cross-section clad profile was defined as a definite integration of a Gaussian function from the moment at which the melt pool was just arriving at the point to the moment at which the point left the melt pool. In the presented experiment, powder of Steel 63 (at 0.63 wt%C) was deposited on a substrate of Steel 20 (at 0.20wt%C) at the laser power of 135 W. The experimental results testified the model.

试验研究了较低功率的激光熔覆成形金属薄壁结构及其影响因素。成形金属薄壁结构的能力对零件薄壁部位的成形和小型零件的制造十分重要。由于传统的激光表面处理工艺观念的影响、对激光单道熔覆成形薄壁结构过程及其规律的认识不够，目前成形薄壁结构的能力较差。试验研究了用与表面处理工艺不同的、功率和光斑尺寸较小的C02激光进行单道熔覆成形薄壁试样，试验结果表明较低功率、较小光斑的激光与适当的扫描速度、送粉速度等配合可以得到壁厚最小为0.4 mm的薄壁结构。激光单道熔覆的壁厚与工艺参数和工件高度有关，粉末流与激光束之间的同轴度和送粉速度的稳定性等因素也影响薄壁结构的成形。

A low-power C02 laser is used to deposit Fe powder and mixture of Fe and carbon powder on substrates respectively, and the macro and micro-structure of the formed samples are investigated. It is demonstrated that most grains of these samples are equi-axed. This is derived from the high nucleation velocity in the shallow melt pool besides rapid solidification of the liquid-state alloy or metal. Bainitic structure, combination of pearlite and ferrite structure and ferrite structure are seen respectively in the samples involving various amounts ofcarbon owing to no martensitic transforma-tion in these small samples.