EFFECT OF VAPOR BLASTING ON FATIGUE LIFE OF AN AGE-HARDENED ALUMINUM-ALLOY

In addition to being used by industry as a means of surface cleaning a nd of imparting a matt finish for subsequent operations, vapour blasti ng has also been, used as a means to improve the fatigue life of parts made of aluminium alloys. The present work investigates the effect of vapour blasting on the fatigue life of age-hardened aluminium alloys, using 6063 aluminium alloy as a model material. It is shown that vapo ur blasting not only produces a hardened surface layer but also roughe ns the surface of the material. This, in turn produces an intricate ef fect on the fatigue life of the material At low blasting pressures, bo th the surface hardness and the depth of hardening increase significan tly while the surface roughness degrades only moderately with blasting pressure. This gives rise to an increase in fatigue life. On further increasing the blasting pressure, however, while the rate of surface h ardening gradually saturates, there is an abrupt increase in the surfa ce roughness due to severe cuts and deep indentations produced by the high velocity abrasive. This causes the fatigue life of the material t o decrease at high blasting pressures. The present work shows that the re exists an optimum blasting pressure beyond which the fatigue Life o f age-hardened aluminium alloys degrades with a further increase in bl asting pressure.