Suitable Na2O-SiO2, BaO-SiO2 Based Coatings for Stainless Steels

Abstract

Two frites with 40 wt.%SiO₂-20 wt.%B₂O₃-17 wt.%Na₂O (G1) and 42wt.%SiO₂-24wt.%BaO-18 wt.%CoO (G2) compositions were prepared and applied on stainless steel by the slurry method. The samples were heated at 950ºC (G2) and 860ºC (G1). The XRD results revealed the sodium silicate and barium silicate phases as well as almost 770 HV, 543 HV microhardness in G1 and G2 coats respectively. The thermal expansion coefficients were α=10.9×10^-6/K(G1) and α=13.31×10^-6/K (G2) respectively. According to EDS results the alkaline earth ions (and CoO) migration into the glass- steel interface was occurred in both coats. The dry sliding friction and wear behavior were investigated using a 4mm diameter AISI52100 steel pin on disk geometry under 5,10 and 18 N loads. The average wear rate were w.r: 32 ×10^-14(m³/N.m) and w.r:5×10^-14(m³/N.m) in G1 and G2 coats. Then two frites were mixed and heat treated at 800ºC with high heating and cooling rate. The resulted composite (G1-G2) shows almost the average wear rate 4×10^-14(m³/N.m), while the coefficient friction of G1-G2 composite was not improved significantly.