Effect of Nitrate Via CVD Coating on Hydrogen Embrittlement in High Strength Steel Treated with Zinc PVD Coating

High strength low alloy steel (HSLAS) is quite sensitive to hydrogen embrittlement due to its different phases. This study investigated the hydrogen embrittlement (HE) behavior of uncoated, physically vapor deposition (PVD) coated, and chemically vapor deposition (CVD) coated HSLAS. The XRD indicates the formation of ZnO, Zn(N3)2, γN and C3N4 phases at the outer coating layer. The results show that combination of surface nitriding and zinc deposition are efficient method against hydrogen embrittlement. This could be attributed to the reduction of hydrogen that is generated by the reaction of surface Zn) N3)2 phase and the low rate of hydrogen transport through the γN phase. The coatings were tested by immersing the tensile samples in a diluted H2SO4 solution with water for 24 hours. Additionally, the result shows that combined coating resulting in higher tensile strength, yield stress, and tensile elongation compared to uncoated samples. Hardness results indicate that the combined coatings (PVD + CVD) has the higher value of about 258 HV, followed by the uncoated sample of about 218 HV, while the PVD only coated sample have the lower hardness value of about 175 HV.