Handbook-Hardsurfacing, Building

3 Restrictions on Bronze-Surfacing. While bronze is often the ideal metal to use in rebuilding surfaces which are subject to sliding friction (working against other smooth surfaces) there are some limitations which must be kept in mind. Temperature is a factor. The types of filler metal normally used for braze welding (such as OXWELD 25M bronze) lose strength rapidly at temperatures above 260⁰C. The surfaces of pistons in internal combustion engines (including diesel engines) seldom exceed this temperature. However, some steam engines operate on superheated steam (supplied at temperatures as high as 350⁰C); for pistons used in such engines, a bronze specifically designed for higher-temperature service, such as OXWELD 31T bronze, should be applied. Another limitation involves the repeated application of bronze surfaces to steel parts subject to alternating tensile and compressive stresses. (This applies to piston rods, but not to pistons). Such parts can be successfully bronze- surfaced once, but repeated application may result in weakening of the steel, due to diffusion of the bronze into the grain structure of the steel.