Development of hardfacing material in Fe-Cr-Nb-C system for use under highly abrasive conditions

The present paper summarises theoretical and experimental work undertaken to develop a hardfacing product designated '167Nb-S'. This material, which is based on the Fe-Cr-Nb-C system, was designed for cladding components subjected to severe abrasive wear by submerged arc welding. The work undertaken includes microstructural characterisation, solidification modelling and abrasion testing. The microstructure of 167Nb-S consists of a large volume fraction of primary niobium carbides, surrounded by a martensitic matrix containing fine quasi-eutectic niobium carbides. Some retained austenite is found along grain boundaries, together with small amounts of intermetallic phase. Alloy development enabled a reduction in the amount of retained austenite and intermetallic phase present in early versions of the alloy, which is beneficial in terms of abrasive wear resistance and weld cracking susceptibility. Standard three body abrasion tests showed that 167Nb-S exhibits wear rates comparable to those of high carbon/high chromium hardfacing deposits with similar hardness. The material 167Nb-S offers many advantages over conventional hardfacing products as high quality multilayer deposits with hardness up to 61 HRC can be deposited crack free, and these remain machinable. A highly successful application of this material is the cladding of roller press rollers, as an alternative to titanium containing hardfacing consumables or segments.