Influence of tin content on tribological characteristics of spray formed Al–Si alloys

In the present investigation, tribological characteristics of spray formed and hot pressed Al–6.5Si, Al–12.5Si and Al–12.5Si–25Sn alloys have been studied. The alloys were spray formed in an environmental chamber using nitrogen gas at 1.0 MPa gas pressure and a deposition distance of 350 mm. The preforms were vacuum hot pressed, at appropriate temperatures, to achieve its densification, The spray formed alloys showed considerable microstructural refinement with uniform distribution of Si particles in Al–Si alloys and that of Sn and Si particles in the matrix of primary α-Al phase of Al–Si–Sn alloys. Dry sliding wear behaviour of these materials was studied as a function of sliding distance, applied load and sliding velocity. The wear response parameters such as wear rate, seizure pressure and frictional force were measured. A pressure-sliding velocity (P–V) limit diagram was established from the data obtained. The P–V diagram indicated that the allowable pressure range for wear seizure increased with increasing Si content. A considerable increase in the wear resistance of the alloy and the seizure pressure is observed with Sn addition. The improved wear properties of the alloy containing Sn are discussed in light of the microstructural features of spray formed alloy and the nature of the debris particles.