Roughness and Hardness of 60/40 Cu-Zn Alloy
— The functional performance of machined components, often, depends on surface topography, hardness, nature of stress and strain induced on the surface, etc. Invariably, surfaces of metallic components obtained by turning, milling, etc., consist of irregularities such as machining marks are responsible for the above. Surface finishing/coating processes used to produce improved surface quality/textures are classified as chip-removal and chip-less processes. Burnishing is chip-less cold working process carried out to improve surface finish, hardness and resistance to fatigue and corrosion; not obtainable by other surface coating and surface treatment processes. It is a very simple, but effective method which improves surface characteristics and is reported to introduce compressive stresses. micro-irregularities start moving in the direction of the newly formed surface. The grain structure is condensed, producing a smoother and harder surface with superior load-carrying and wear-resistant capabilities. 2 + 0.0525X 4 + 0.0125X 1 X 4 − 0.02X X 4 − 0.0375X 3 X 4 Hv=160.625 − 2.37 5X 1 + 5.125X 2 + 1.875X 3 + 4.375X 4 − 1.625X 1 X 4 + 4.375X 2 X 4 − 2.375X 3 X 4 High surface microhardness (175H V ) was obtained at 400rpm, 2passes, 0.05mm/rev and 15kgf., and high surface finish (0.20µm) was achieved at 30kgf, 0.1mm/rev, 112rpm and single pass. In other words, surface finish improved by 350% and microhardness improved by 21% compared to as machined conditions.
An Investigation into Roller Burnishing
Abstract Burnishing, a plastic deformation process, is becoming more popular as a finishing process: thus, how to select the burnishing parameters to reduce the surface roughness and to increase the surface microhardness is especially crucial. This paper reports the results of an experimental program to study the influence of different burnishing conditions on both surface microhardness and roughness: namely, burnishing speed, force, feed, and number of passes. Also, it reports the relationship between residual stress and both burnishing speed and force. The residual stress distribution in the surface region that is orthogonally burnished is determined using a deflection etching technique. Mathematical models are presented for predicting the surface microhardness and roughness of St-37 caused by roller burnishing under lubricated conditions. Variance analysis is conducted to determine the prominent parameters and the adequacy of the models. From an initial roughness of about Ra 4.5 μm, the specimen could be finished to a roughness of 0.5 μm. It is shown that the spindle speed, burnishing force, burnishing feed and number of passes have the most significant effect on both surface microhardness and surface roughness and there are many interactions between these parameters. The maximum residual stress changes from tensile to compressive with an increase in burnishing force from 5 to 25 kgf. With a further increase in burnishing force from 25 to 45 kgf, the maximum residual stress increases in compression.
Flocculation tests with electrophoretically separated serum proteins.
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