Papers by Keyword: Laser Coating

Abstract: The thesis researches on repeated impact and deformation by using self-made repeated impact fatigue tester and selecting four groups of coating test specimen with different thickness. The thesis finds that test specimen have epistrophe effect under the deformation rules of repeated impact loading. And different coating test specimen with different thickness result in different results under the same repeated impact conditions: the total depths, total strain, deformation hardening degrees and deformation hardening depths are different. It is proposed that coating thickness should be increased to improve the ability of materials resisting repeated impact and deformation within a certain range. As to this experiment, the optimal coating thickness of specimen is obtained by preliminary analysis.

Abstract: The laser heat treatment is a processing method of heat treatment on the surface of the metal part with a higher power density laser beam, mainly including laser surface hardening , laser annealing , laser surface alloying(lsa) and laser surface coating, it is width applied to machinery manufacturing, equipment maintenance, mold manufacturing, etc. It has gradually been recognized and adopted because of its unique characteristics.In this paper, focusing mirrors for improved key-parts of the laser heat treatment equipment have been analyzed and introduced, and pointed out the problems which should be noticed in the improvement.

Abstract: Coating samples prepared by laser cladding were subjected to repeated impact fatigue experiment. It is observed through phenomenological analysis that most coating cracks are original from the surface. And then, the cracks extend by the combined action of coating inner stress and repeated impact compression stress. The formation of crack is close related to performance of coating material. It can be divided to traversed crack and reticular crack from surface side; it also can be divided to vertical extend crack and reticular extend crack from the cross section side. Rigid and brickle coating has a shorter repeated impact life because a kind of linear crack is formed easily in it. On the other hand, tougher coating has a long life. Mechanics of nucleation and expansion of crack was explained by using stress concentration theory and vacancy concentration theory. The anti-repeated impact fatigue performance of laser cladding part could be improved by increasing toughness and reducing hardness of the coating material. Furthermore, suitable dispersion strengthening and fine-crystal strengthening can obtain the same purpose.

Abstract: The surface texture of sheet steel plays an important role for automotive applications. To achieve appropriate surface topographies and press-forming behaviour, a new laser coating texturing (LCT) technique aimed at texturing steel work-rolls was proposed. The laser texturing process was realized by applying laser pulses at very high repetition rates to produce innumerable micro-craters with the required shape profile on the surface of the rolls. Moreover, the surface alloying of the dimples was carried out on the substrates of bearing steel GCr15. The submicron WC-Co alloy metal powder was melted into the micro-craters by high laser energy. The effects of processing parameters on the properties of the laser textured samples were investigated. The dimpled surfaces were examined by a 3-dimensional surface profilometer. Microstructures of the coating layers were assessed by optical and scanning electron microscopy. The experimental investigations show that the laser-dimpled hard-coated surfaces exhibit compatible metallurgical interfaces with the substrates. The laser coating textured roll is demonstrated to have excellent abrasion resistance and a much longer service life. The abrasive wear resistance was 5 times higher than that of the substrates. The average surface microhardness values were as high as 700HV.