Ti-Si-N hard coatings were deposited on steel substrates by reactive unbalanced magnetron sputtering from Ti and Si elemental targets in a mixture of Ar and N2 gases.The influences of negative bias voltage(in the range of-30 to-80 V)on the mechanical properties of the coatings were investigated.In particular,the critical cycle during dynamic impact tests was employed to indicate the bonding strength of the coatings.It was found that the Ti-Si-N coatings prepared at lower constant bias voltages could effectively improve the adhesion and the cyclic impact performance,but their hardness was dropped significantly to 13 GPa at a bias of-30 V.Higher bias voltage values induced greater hardness.A maximum hardness of 47 GPa was obtained at a bias of-60 V.However,the coating adhesion was worse in this case,and the number of impact cycles(～8×10 3)that the coatings could endure was much shorter than that of TiN binary coatings(～2×104).On the other hand,the bias voltage was varied linearly from-40 to-60 V during Ti-Si-N deposition.Under this circumstance,the hardness of the coatings deposited with the bias-graded configuration remained very high(42 GPa),and the adhesion strength was improved substantially.Also,the critical impact cycle could reach as high as 1.8×104.Therefore,bias-graded deposition can provide an effective processing route to prepare Ti-Si-N superhard coatings with high adhesion strength and impact resistance. Ti-Si-N hard coatings were deposited on steel substrates by reactive unbalanced magnetron sputtering from Ti and Si elemental targets in a mixture of Ar and N2 gases. The influences of negative bias voltage (in the range of -30 to -80 V) on the mechanical properties of the coatings were investigated. In particular, the critical cycle during dynamic impact tests was employed to indicate the bonding strength of the coatings. It was found that the Ti-Si-N coatings prepared at a lower voltage improve the adhesion and the cyclic impact performance, but their hardness was dropped significantly to 13 GPa at a bias of -30 V. Heigher bias voltage values ​​may cause greater hardness. However, the coating adhesion was worse in this case, and the number of impact cycles (~ 8 × 10 3) that the coatings could endure was much shorter than that of TiN binary coatings (~ 2 × 104) .On the other hand, the bias voltage was varied linearly f The rom-40 to-60 V during Ti-Si-N deposition. Under this circumstance, the hardness of the coatings deposited with the bias-graded configuration very very high (42 GPa), and the adhesion strength was improved substantially. Als, the critical impact cycle could reach as high as 1.8 × 104.Therefore, bias-graded deposition can provide an effective processing route to prepare Ti-Si-N superhard coatings with high adhesion strength and impact resistance.