Abstract: Fe-Cr-C alloy system is a kind of excellent hardfacing material,but for a long time the difficult problems of low toughness,high cracking liability and low ability lo withstand biller impact have not yet been solved.The aulhors found that by introducing proper amount of potassium (K) alloy into the coatings or cores to modify the hardfacing matels,the problems menlioned above can be effectively solved.This method worked well in engineering practice.The introduction of K-alloy changed the matrix micro-structures from martensite and austenite to hardened auslenite.As the fluctuation of Cr content in austenite,the TEM analysis and electron diffraction pattern revealed,the tiny dispersed hard phase of (Cr,Fe)₇C₃ was the cause of the modification austenite hardening.Moreover,K-alloy can break and isolate the shapes of eutectic.This is why the properties of the Fe-Cr-C hardfacing alloy was improved.