Abstract
Ti 1−x (Al y Si 1−y ) x N coatings covering a wide compositional range, 0.38 < x < 0.76 and 0.68 ≤ y ≤ 1.00, are deposited to investigate the influence of Al + /Si + ion irradiation on microstructural and mechanical properties. The samples are grown in Ar/N 2 atmosphere by the hybrid high-power impulse and dc magnetron co-sputtering (HiPIMS/DCMS) method with substrate bias synchronized to the Al + /Si + -rich portion of the HiPIMS pulses. Two Ti targets are operated in DCMS mode, while one AlSi target is operated in HiPIMS mode. Four different AlSi target compositions are used: Al 1.0 Si 0.0 , Al 0.9 Si 0.1 , Al 0.8 Si 0.2 , and Al 0.6 Si 0.4 . X-ray diffractometry reveals that films without Si (i.e., y = 1.0) have high Al solubility in NaCl-structure, c-TiAlN, up to x ≤ 0.67 no w-AlN is detected. Once Si (y < 1.0) is introduced the Al solubility limit decreases, but remains higher than other PVD techniques, along with grain refinement and the formation of a SiN z rich tissues phase, as shown by transmission electron microscopy. The nanoindentation hardness is high (~30 GPa) for all films that do not contain the w-AlN phase. All the coatings have compressive stresses lower than −3 GPa. Interestingly, a range of films with different compositions displayed both high hardness (~30 GPa) and low residual stress ( σ < 0.5 GPa). Such a unique combination of properties highlights the benefits of using HiPIMS/DCMS configuration with metal-ion-synchronized substrate bias, which utilizes the Al + /Si + supplantation effect and minimizes the Ar + incorporation. • TiAlSiN films are grown by AlSi-HiPIMS/Ti-DCMS with wide compositional range. • Substrate bias is synchronized to the Al + /Si + -rich portion of the HiPIMS pulses. • The Al + /Si + irradiation effects on film properties are studied. • High Al and Si solubilities in c-TiAl(Si)N are achieved without w-AlN formation. • Specific films yield the combination of low residual stress and high hardness.
Highlights
Transition metal nitride-based materials have proven to be effective protective layers when applied on cutting tool inserts
The time evolution of Al+/Ar+ is slightly different for the three targets and in order to perform the growth under similar conditions we identified a time window from 30 to 130 μs that provides high Al+/Ar+ ion ratios for all AlSi targets
The grain refinement caused by the formation of SiNz tissue phase and w-AlN precipitation occurs at lower x values with increasing solubility limit of TiAl (Si) content
Summary
Transition metal nitride-based materials have proven to be effective protective layers when applied on cutting tool inserts. The coating performance can be further enhanced by mixing TiAlN and TiSiN to produce quaternary TiAlSiN alloys, taking advantage of hardening mechanisms mentioned above, while being resistant to oxidation This approach has shown limited success due to the difficulties associated with simulta neous phase and nanostructure control in these metastable systems. Wu et al [20] successfully synthesized cubic Al-rich TiAlSiN coatings with a maximum metal atomic ratio of Al/(Al + Ti) = 0.59 and Si content of 9.4 at.% in an Al-HiPIMS/TiSi-DCMS setup with substrate bias synchronized to Al+-rich pulses This indicates that the hybrid HiPIMS/DCMS co-sputtering setup with synchronized sub strate bias pulses to the metal-ion-rich portion of the HiPIMS pulses enables the synthesis of metastable transition metal nitrides that exhibit a NaCl structure with a wider compositional range than what is possible to achieve with conventional sputtering techniques. By using four AlSi targets with varying Al/Si ratios and independently varying the DCMS power we were able to map out a wide compositional range, i.e., 0.38 < x < 0.76 and 0.68 ≤ y ≤ 1.00 and identify a parameter space in which deposited films possess a unique combination of low compressive stress (
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