Tham khảo tài liệu 'surface quality aspects_5', kỹ thuật - công nghệ, điện - điện tử phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Roughness and Profile of Substrates 381 a Fig. Substrate profile modification due to acid etching Neal 1999 . a Before etching b After etching number of experimental results for different profile parameters for blast cleaned steel substrates. The blast cleaning process generates isotropic surfaces in contrast to grinding and polishing that form anisotropic surfaces. These relationships can be recognised if polar plots of treated surfaces are evaluated. A polar plot of a steel surface treated with different methods is shown in Fig. . The shape of the plot characterises the surface type. The elliptic shape for the polished surface inner plot is typical for an anisotropic surface. The value for the profile parameter peak spacing depends on the measurement direction it is high in 90 -direction. The polar plots for the blast cleaned surfaces in contrast are of circular shape. The value of the profile parameter 382 8 Surface Quality Aspects Table Wettability of IN718 after surface treatment wetting liquid AMS4777 Solomon et al. 2003 _ __ Blast cleaning process Maximum wetting force in N m With Al2O3 With Al2O3 polishing with paper 400 pm does not depend on the measuring direction. The diameters of the circles express the peak spacing values in the example shown in Fig. . Doherty 1974 delivered a more detailed study about the effects of blast cleaning parameters on the isotropy of blast cleaned substrates. He found that blast cleaning angle and abrasive material greatly influenced isotropy. This author also distinguished blast cleaned substrates into two types normal type which is isotropic and machine type which is anisotropic . Normal type areas showed a highly disturbed random surface this type was produced when large blasting angle and smaller abrasive particles were used. Machine type areas in contrast had a directionality that varied a little to each
