Welded joint in which the weld metal and parent material have significant differences in mechanical properties and/or chemical composition. Example: A repair weld of a cast iron item performed with a nickel-based electrode.
Heterogeneous welding is one way of performing fusion welding with the application of external filler whose metallurgical composition is substantially different from that of the base metals. So if filler material is applied during joining and the metallurgical composition of filler is different from that of the base metal then it is termed as heterogeneous welding. It is to be noted that heterogeneous welding is not a particular type of welding process like SMAW, TIG, GMAW, etc.; instead, it is one of the three different modes or ways of doing fusion welding.
Brazing and soldering are common examples of heterogeneous joining. Manual Metal Arc Welding (MMAW), Gas Metal Arc Welding (GMAW), Flux Cored Arc Welding (FCAW), etc. can also be performed in heterogeneous mode.
Advantages of heterogeneous welding
- Various weld properties, such as stress and corrosion resistance, etc. can be enhanced by choosing appropriate filler material.
- Thick plates can be welded efficiently with proper edge preparation.
- Strength of the joint is excellent—better than autogenous welding.
- Due to sufficient supply of molten metal, tendency of crack formation during solidification reduces.
- Welding of various joints, like butt joint, lap joint, tee joint, corner joint, etc. are also possible.
- Joints are more reliable, so less chance of failure if welded properly.
Disadvantages of heterogeneous welding
- Because of the non-uniformity in composition among the filler and base metals, there exist high tendency of development of weld discontinuity and crack formation.
- Compatibility between filler material and base material must be checked properly otherwise defective welding will be produced.
- Filler material is usually costlier and it also requires proper maintenance.
- Application of excess filer material causes high reinforcement on weld bead, which are required to remove after welding by grinding.
- Appearance of weld bead is not good.
- Sputter may also produce if process parameters are not chosen optimally.