CHROMIUM DIFFUSION COATINGS FOR THE PROTECTION OF LOW-ALLOY STEEL IN A SULFIDIZING ATMOSPHERE

The chromium diffusion process was investigated for carbon-, low-alloy and austenitic type steels. The quality of the diffusion coatings on low-alloy steels was tested using four criteria that reflect in-servic e reliability of heat exchangers in coal gasifiers: thermal stability, ductility, resistance to down-time corrosion and weldability. These t ests have shown that good quality diffusion coatings can be made on 10 CrMo 910. The corrosion resistance of the chromium diffusion coatings can be greatly enhanced by the presence of small amounts of carbide f ormers like vanadium and niobium.