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In this study, a martensitic stainless steel plate of 10 mm thick was welded by keyhole plasma transfer arc (PTA) welding technique both itself and using austenitic stainless steel plate of 2 mm thick in interface. So, penetration depth, microstructure, mechanical behavior and interface layer effects of keyhole plasma welding were investigated. After keyhole plasma welding, microstructural analysis including metallographic examination, and notch impact strength tests were performed. From the results, it was seen that with this technique can be obtained penetration depth of 8 mm without any pretreatment of welding. Also, austenitic stainless steel interface layer was raised impact strength of welding.

In the present study, a gray cast iron and a medium carbon steel couple were diffusion bonded at the temperatures of 850, 900, 950 and 1000 °C under a pressure of 8 MPa for 30 min, and the effects of temperature and high heating and cooling rate on interface formations and microstructure were investigated. After diffusion bonding, scanning electron microscopy, shear test measurements and microhardness measurement of interface region were made. The microstructure at the inside of medium carbon steel of bonded couple consisted of martensite. As a result, from the microstructural observations, a good bonding along the interface of the bonded couples and the interface is free from voids and microcracks.