Document deals with the weldability of creep resistant gradient tubes with increased fire side corrosion. Gradient tubes, made of 11CrMo9-10 low alloy body and 347H austenitic shell, are devoted for boilers burning aggressive flue gases/ashes producing feedstock, e.g. biomass/chip/straw boilers. The gradient tubes (38mm outer diameter, 5mm wall thickness from which austenitic shell is ~1mm thick) were used for TIG (GTAW) welding. Manual weld deposits made of a) austenitic weld metal; b) the combination of low alloy (root + filling passes) and austenitic (cap); were investigated. The weld deposits were manufactured according to best practice and evaluated in line with WPQRs requirements. In addition, high temperature corrosion tests, scanning electron microscopy and EDX analysis were employed in order to understand all metallurgical aspects of gradient tubes welds. The weld deposits fulfilled all WPQR requirements. However, the weld properties are based on compromise between mechanical properties and corrosion behaviour.