Abstract:
An article includes a substrate and a hard film formed on the substrate; the hard film includes a plurality of complex layers and a plurality of Ni layers, each complex layer and Ni layer alternately arranged; each complex layer includes a plurality of TiAlN layers and a plurality of CrAlN layers, each TiAlN layer alternately arranged with each CrAlN layer. The disclosure also described a method to make the article.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is related to co-pending U.S. patent application (Attorney Docket No. US36048) entitled “ARTICLE HAVING HARD FILM AND METHOD FOR MAKING THE ARTICLE”. Such application has the same assignee as the present application. The above-identified application is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to an article having hard films and a method for making the article. 
         [0004]    2. Description of the Related Art 
         [0005]    Hard films are widely applied on surface of the metal alloys, steels and ceramics to fabricate articles with high hardness and high abrasion resistance. Currently, a common hard film is TiAlN film. However, to meet the needs for maximum hardness for special articles, such as cutting tools, the TiAlN film does not meet this requirement for hardness and abrasion resistance. 
         [0006]    Therefore, there is room for improvement within the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the present disclosure article having hard film and method for making the article can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0008]      FIG. 1  is a sectional view of an article having hard film according to an exemplary embodiment. 
           [0009]      FIG. 2  is a flow chart to fabricate the article shown in  FIG. 1 . 
           [0010]      FIG. 3  is a vertical view of a coating machine used to fabricate the article. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]      FIG. 1  shows an exemplary embodiment of an article  10 . The article  10  includes a substrate  11  and a hard film  12  integrally formed on the external surface of the substrate  11 . The substrate  11  can be metal alloy, stainless steel, or ceramic. 
         [0012]    The hard film  12  can be formed on the substrate  11  by Physical Vapor Deposition (PVD). The hard film  12  includes a plurality of alternating complex layers  120  and Ni layers  130 , each complex layer  120  is alternately arranged with each Ni layer  130 . Each complex layer  120  includes a plurality of alternating TiAlN layers  121  and CrAlN layers  122 , and each CrAlN layer  122  alternately arranged with each TiAlN layer  121 . Each complex layer  120  includes an equal number of TiAlN layers  121  and CrAlN layers  122 , typically in the range of about 5-8 of each, having a total thickness in a range from about 8 nanometer(nm) to about 20 nm. Each Ni layer  130  has uniform thickness in a range from about 20 nm to about 40 nm, each Ni layer  130  is located between and transitionally connects two adjacent complex layers  120  to relieve the inner stress of the hard film  12 . The hard film  12  has a total thickness in a range from about 1.5 micrometer (μm) to about 3 μm. Since the thermal expansion rate of the TiAlN layer  121 /the CrAlN layer  122  is close to the thermal expansion rate of the substrate  11 , one of the TiAlN layer  21  or the CrAlN layer  122  is directly formed on the substrate  11 , thus avoiding production of large inner stresses during variations in the temperature of the article  10 . The TiAlN layer  121  or the CrAlN layer  122  has excellent hardness, thus, a TiAlN layers  121 /the CrAlN layer  122  is made the outermost layer of the article  10 . 
         [0013]    Referring to  FIG. 2 , the article  10  can be made from following steps: 
         [0014]    Providing a substrate  11 . The substrate  11  may be made of metal alloy, steel, or ceramic. The substrate  11  is cleaned by a cleaning solution to clean grease from the surface of the substrate  11 . The cleaning solution can be ethanol, acetone and/or other organic solvents. A common ultrasonic cleaning machine can be used for cleaning the substrate  11 . 
         [0015]    Providing a vacuum sputtering coating machine  100  Referring to  FIG. 3 , the vacuum sputtering coating machine  100  includes a sputtering coating chamber  20  and a vacuum pump  30  connecting to the sputtering coating chamber  20 . The vacuum pump  30  is used to pump air out the sputtering coating chamber  20 . The vacuum sputtering coating machine  100  further includes a rotating bracket  21 , two first targets  22 , two second targets  23 , two third targets  24 , and a plurality of gas inlets  25 . The rotating bracket  21  rotates the substrate  11  in the sputtering coating chamber  20  relative to the first targets  22 , the second targets  23 , and the third targets  24 . The two first targets  22  face each other, and are respectively located on opposite sides of the rotating bracket  21 , the same as the two second targets  23  and the two third targets  24 . In this exemplary embodiment, the first targets  22  are TiAl alloy targets, the second targets  23  are CrAl alloy targets, the third targets  24  are Ni targets. 
         [0016]    Cleaning the targets  22 ,  23  and  24  by argon(Ar) plasma. The vacuum level inside the sputtering coating chamber  20  is set to about 3.0*10 −3  Pa. Argon is fed into the sputtering coating chamber  20  at a flux rate about 500 Standard Cubic Centimeters per Minute (sccm) from the gas inlets  24 . A bias voltage applied to the substrate  11  may be between about −250 volts (V) and about −350 volts. The current intensity of the first target  22 , the second target  23  and the third targets  24  are respectively set to about 30-50 A (Ampere). The Ar particles strike against and clean the surface of the first targets  22 , the second targets  23  and the third targets  24 . 
         [0017]    Depositing the hard film  12  on the substrate  11  as follows. Depositing the complex layer  120  on the substrate  11 . The vacuum level inside the sputtering coating chamber  20  is set to about 3.0*10 −3  Pa. A bias voltage applied to the substrate  11  is adjusted to between about −250 volts and about −450 volts. Argon and Nitrogen (N 2 ) are fed into the sputtering coating chamber  20 , with Argon at a flux rate about 300 sccm, and Nitrogen at a flux between about 80 sccm and about 150 sccm. The first targets  22  and the second targets  23  are evaporated respectively at a current intensity between about 30 A and about 45 A. The rotating bracket  21  is started at a speed between about 0.5 revolutions per minute(r/min) and about 3 r/min. The first targets  22  and the second targets  30  in the sputtering coating chamber  20  are alternatively evaporated for a time from about 60 min to about 120 min, to alternatively deposit an equal number of alternating TiAlN layer  121  and CrAlN layer  122  on the substrate  11 . 
         [0018]    Depositing the Ni layer  130  on the complex layer  120 . The third targets  24  are evaporated at a current intensity between about 20 A and about 30 A for a time between about 60 second(s) and about 120 s, to deposit the Ni layer  130  on the complex layer  120 . 
         [0019]    Alternately depositing the complex layer  120  and the Ni layer  130  as said, to deposit the hard film  12  on the substrate  11 , until the hard film  12  has a thickness in range from about 1.5 μm to about 3 μm. The complex layer  120  is directly combined on the substrate  11  and is made the outermost layer of the article  10 . 
         [0020]    It is to be understood that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of assemblies and functions of various embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.