Abstract
The bond strength of sprayed metal coating was determined by means of tensile test.
The specimen consisted essentially of a shaft which were provided with a hole clear through its axis.
A stud was fitted in this hole, with one end to the flat surface of the shaft. The flat surface of shaft and hence the end of stud were pretreated all over. After bonding and spraying, the stud was pulled out of the shaft by means of testing machine. A breaking load Pmaz as indicated on the testing machine is concentrated around the end of the stud, from where the bond layer was sheared off. After Pmax was measured, smaller loads than Pmax were continued to shear off the rest of the bond layers, until the stud was pulled out of the shaft.
The strength of the bond (FB) layer (h mm thick) is given by
FB=h⋅fBmax=Pmax/πd kg/mm
where, d is a diameter of the end of the stud in mm, and fBmax is the maximum stress of bond layer. Being represented in FB or h⋅fBmax, the bond strength of coating per unit length can, in any case, be measured by Pmax/πd.
The readings for d were 40, 20, 10, 5 and 4mm which meant that the maximum value of the bond strength between the metallic coating of 13 Cr stainless steel (about 1.5mm thick) and the base metal of 0.2 C mild steel prepared by spraying with molybdenum was about 8kg/mm in any case of d. If the bond strength is given by Pmax/π/4d2kg/mm2, the value will vary with d.
