Which of following holds true for friction welding?

Following are the few reasons to consider friction welding over other techniques:
? The machine-controlled process eliminates human error, and weld quality is independent of operator skill.
? It?s ecologically clean?no objectionable smoke, fumes, or gases are generated that need to be exhausted.
? No consumables are required? no flux, filler material, or shielding gases.
? Power requirements are as low as 20% of that required of conventional welding processes.
? Since there is no melting, no solidification defects occur, e.g. gas porosity, segregation or slag inclusions.