| Laser rapid repair (LRR) is an advanced laser repair technology that has been developed based on Laser rapid forming (LRF). LRR introduces the forming principle of LRF to the repairing of the component, the impairment can be repaired through cladding the similar powder to damaged surface depend on outline of damaged parts, and the original outline dimension and properties can be reproduced. In this paper, LRR of Ti-6A1-4V (TC4) alloys, that was extensively used in aviation industry, astronavigation industry, energy industry and chemical indurstry et al., was experimentally investigated, the repairing technology characteristics were analyzed, the formation mechanism and the effect on the mechanical properties of ill bonding were studied. The main results are as follows:(1) The effects of laser processing parameters, i.e. laser power, scanning velocity and powder feed rate, on the height of single cladding layer, the width of single clad and shape coefficient of cladding layer (ζ) were investigated experimentally. The optimum selection range of processing parameters for laser rapid repairing of TC4 titanium alloy was determined according to the requirements of laser rapid repairing on heat input coefficient and shape coefficient of cladding layer.(2) The formation mechanism of ill-bonding was analyzed. It is found that the match between overlap and Z increment have an important influence on the formation of ill-bonding. The effects of laser power, scanning velocity and powder feed rate on the formation of ill-bonding is realized indirectly through their effects on the match between overlap and Z increment. The shape, size and distribution of ill-bonding were also studied. It is shown that ill bonding appears between layer and layer or track and track. The shape of ill bonding between layer and layer was shown as V shape, the shape of ill bonding between track and track was shown as rectangle. The size of ill bonding increases with the decrease of overlap and the...
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