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A Quantitative Approach To Assess High Temperature Flow Properties Of A Pa 12 Powder For Laser Sintering
摘要： In order to consider thermal conditions involved in laser sintering (LS), the effect of temperature on the flow properties of a polyamide 12 powder was assessed. Shear tests were carried out at temperatures from ambient up to values close to the melting temperature of the polymer. The measurement method provides quantitative descriptors of powder flowability. Experiments indicate that flowability significantly deteriorates when temperature rises and approaches a value of about 20°C lower than the melting temperature. The spreading process may be hindered by natural agglomeration of the material. A simple analysis based on the extrapolation of the bulk flow properties at zero consolidation shows that agglomeration is excluded in the temperature range between 100 and 140°C. This turns out to be the range in which it is known that the material can be used safely for LS applications.
关键词： powder bed fusion,powder flow,flow function,high temperature,agglomeration
更新于2025-09-23 15:19:57
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On the formation features, structure, microhardness and tribological behavior of single tracks and coating layers formed by laser cladding of Al-Fe powder bronze
摘要： In this paper, the effect of the gas flow and pressure on the powder flow, as well as the effect of the conditions of laser cladding on the microstructure, phase composition, microhardness and tribological behavior of an Al-Fe powder bronze coating, is studied. The features of single tracks, single- and double-layer coatings are described. The speed of a laser beam, the pitch of the single track and the distance between the nozzle and the coated surface affect the microstructure and microhardness of the coating. These parameters are more stable for double-layer coatings because a denser coating with better fusing along the grain boundaries is formed as a result of secondary melting. Under dry friction conditions, with deposition speeds less than 140–160 mm/min, the coefficient of the friction is stable and significantly lower compared with cast aluminium bronzes. In such conditions, the wear resistance of the coating increases with the increase in deposition speed. With further speed increases, a substantial rise in the friction coefficient in time and a substantial seizure of friction surfaces are observed. Under lubricated friction conditions, when the load increases from 120 N to 360 N, that is, where the pressure on the contact surface increases from 1.75 to 5.3 MPa, a sharp increase in the wear rate occurs with a deposition speed of 120 mm/min almost 130-fold and for a speed of 140 mm/min ~9-fold.
关键词： Al-Fe bronze,Powder flow,Single- and double-layer coating features,Laser cladding,Tribological behavior,Single track features
更新于2025-09-09 09:28:46