Abstract:
An iron-based alloy for use in a plasma transferred wire arc thermal spray apparatus includes a high sulfur steel alloy in a stainless and non-stainless forms including a high aluminum and high titanium content. The alloy has significant improvements in the elimination of spray coating cracking, reduction of machining cost, and improved lubrication performance.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to ferrous metallurgy and more particularly to ferrous alloy compositions for use in thermal spray metal deposition methods. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    A typical thermal spray method uses many types of metal compositions in order to achieve particular finished mechanical properties. In some applications, the alloy coating is machined after the thermal spray process. For example, a thermal spray coating of a cylinder bore of an engine block requires a first machining operation to size the bore for proper piston fit. A second machining operation may be employed to impart a particular surface finish or pattern on the surface of the alloy coating for lubrication and wear resistance. 
         [0004]    While current thermal spray material compositions achieve their intended purpose, the need for new and improved material compositions which exhibit improved performance, especially from the standpoints of coating cracking, machinability, lubrication, and mechanical properties, is constant. Accordingly, there is a need in the art for an improved thermal spray material composition that improves upon these performance properties. 
       SUMMARY 
       [0005]    The present invention is an iron-based alloy for deposition onto a metal surface such as aluminum using a plasma transferred wire arc thermal spray apparatus. The alloy includes Carbon C in the amount from about 0.10 to about 0.75 wt %, Manganese Mn in the amount from about 0.50 to about 2.50 wt %, Silicon Si in the amount from about 0.30 to about 1.50 wt %, Aluminum Al in the amount from about 0.40 to about 3.00 wt %, and Sulfur S in the amount from about 0.10 to about 0.35 wt %. The balance of the alloy is Iron Fe. 
         [0006]    In another example of the present invention, the alloy further includes Carbon C in the amount from about 0.15 to about 0.75 wt %, Chromium Cr in the amount from about 0.00 to about 3.00 wt %, Molybdenum Mo in the amount from about 0.00 to about 1.00 wt %, Silicon Si in the amount from about 0.30 to about 1.50 wt %, Aluminum Al in the amount from about 0.40 to about 3.00 wt %, Titanium Ti in the amount from about 0.00 to about 1.00 wt %, and Sulfur S in the amount from about 0.10 to about 0.35 wt %. The balance of the alloy is Iron Fe. 
         [0007]    In yet another example of the present invention, the alloy further includes Carbon C in the amount from about 0.28 to about 0.35 wt %, Manganese Mn in the amount from about 1.35 to about 1.65 wt %, Chromium Cr in the amount from about 0.95 to about 2.00 wt %, Molybdenum Mo in the amount from about 0.00 to about 0.40 wt %, Silicon Si in the amount from about 0.50 to about 1.00 wt %, Aluminum Al in the amount from about 1.10 to about 1.40 wt %, Titanium Ti in the amount from about 0.00 to about 0.60 wt %, Sulfur S in the amount from about 0.24 to about 0.33 wt %, and Phosphorus P in the amount from about 0.00 to about 0.03 wt %. The balance of the alloy is Iron Fe. 
         [0008]    In yet another example of the present invention, the alloy further includes Carbon C in the amount from about 0.25 to about 0.30 wt %, Manganese Mn in the amount from about 1.35 to about 1.65 wt %, Silicon Si in the amount from about 0.50 to about 1.00 wt %, Aluminum Al in the amount from about 1.10 to about 1.40 wt %, Sulfur S in the amount from about 0.24 to about 0.33 wt %, and Phosphorus P in the amount from about 0.00 to about 0.03 wt %. The balance of the alloy is Iron Fe. 
         [0009]    In yet another example of the present invention, the alloy further includes Carbon C in the amount from about 0.10 to about 0.60 wt %, Manganese Mn from about 1.00 to about 2.00 wt %, Chromium Cr from about 8.00 to about 30.00 wt %, Molybdenum Mo from about 0.00 to about 3.00 wt %, Silicon Si from about 0.30 to about 1.50 wt %, Aluminum Al from about 0.40 to about 3.00 wt %, Titanium Ti from about 0.00 to about 1.00 wt %, Sulfur S from about 0.10 to about 0.33 wt %, and Nickel Ni from about 0.00 to about 14.00 wt %. The balance of the alloy is Iron Fe. 
         [0010]    In yet another example of the present invention, the alloy is formed into one of a wire and a powder for use in a plasma transferred wire arc thermal spray apparatus. 
         [0011]    In yet another example of the present invention, the alloy is deposited onto a cylinder wall of a cylinder block of an internal combustion engine. 
         [0012]    In yet another example of the present invention, the cylinder block is manufactured from a cast aluminum alloy. 
         [0013]    The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0014]      FIG. 1  is a perspective view of a cylinder block for an internal combustion engine in accordance with the present invention; 
           [0015]      FIG. 2  is a cross section of a coated cylinder bore wall of a cylinder block in accordance with the present invention; and 
           [0016]      FIG. 3  is a table of alloy compositions for use in the coating of the cylinder bore wall in accordance with the present invention. 
       
    
    
     DESCRIPTION 
       [0017]    Referring to  FIG. 1 , a cylinder block for an internal combustion engine, generally indicated by reference number  10 , is illustrated and will now be described. The cylinder block  10  has several major features including a plurality of cylinder bores  12 , a crankcase portion  14 , a head deck  16 , a water pump portion  18 , a pan rail  20 , and bearing caps  22 . More specifically, the plurality of cylinder bores  12  can include from two cylinder bores to sixteen or more cylinder bores. In this example, four cylinder bores  12  are aligned such that each axis of the cylinder bores  12  are parallel to each other. In other examples, the cylinder bores  12  may be arranged in the shape of a “V”, flat, or other arrangements without departing from the scope of the invention. A top end of each cylinder bore  12  terminates at the head deck  16  while the bottom end of each cylinder bore  12  terminates at the crankcase portion  14  of the cylinder block  10 . 
         [0018]    Turning now to  FIG. 2  with continuing reference to  FIG. 1 , a cross section of a cylinder bore wall  24  is illustrated and will now be described. The cylinder bore wall  24  includes an inner surface or circumference  26  and an outer surface  28 . The outer surface  28  may be adjacent to a cavity utilized as water cooling passages or it may be utilized as a cylinder bore wall  24  of the adjacent cylinder bore  12 . In either aspect, the inner surface  26  of the cylinder bore wall  24  is exposed to a reciprocating piston (not shown) when in operation. The inner surface  26  of the cylinder bore wall  24  includes a coating  30  of material that is bonded to a parent material of the cylinder bore wall  24 . In some examples, the parent material of the cylinder bore wall  24  may be a cast iron alloy or an aluminum alloy. However, other types of alloys may be used without departing from the scope of the invention. The coating  30  is bonded to the parent material of the cylinder bore wall  24  using any one of a number of methods. One such method is a plasma transferred wire arc thermal spray apparatus as explained in U.S. Pat. No. 5,938,944. Other similar methods or variations of the disclosed methods may be used without departing from the scope of the invention. After the coating  30  is applied to the inner surface  26  of the cylinder bore wall  24 , an inner surface  32  of the coating  30  may be machined to achieve a precise fit with the piston and achieve a prescribed surface finish or hone pattern. 
         [0019]    Turning now to  FIG. 3  with continuing reference to  FIG. 2 , a number of example alloys are shown in table format and will now be described. The alloys 1-4 are prepared in wire or powder form and used in the thermal spray apparatus to deposit the alloys 1-4 on the inner surface  26  of the cylinder bore wall  24  to form the coating  30 . Example Alloy 1 is based on a carbon steel alloy in particular having Carbon C in the range of about 0.15 to about 0.75 weight percent wt %, Manganese Mn in the range of about 0.50 to about 2.50 wt %, Chromium Cr at about 3.00 wt % maximum, Molybdenum Mo at about 1.00 wt % maximum, Silicon Si in the range of about 0.30 to about 1.50 wt %, Aluminum Al in the range of about 0.40 to about 3.00 wt %, Titanium Ti at about 1.00 wt % maximum, and Sulfur S in the range about 0.10 to about 0.35 wt % with the balance Iron Fe. More specifically, the Carbon C content is prescribed to improve strength and overcome cracking of the finished coating  30 . Manganese Mn is prescribed for promoting martenisitic transformation during coating cooling, and Molybdenum Mo for improved lubrication and pitting resistance, and Aluminum Al and Titanium Ti content is prescribed to tailor oxides formed in the thermal spraying process. The Aluminum oxide Al 2 O 3  and Titanium oxide TiO 2  aid in the wear properties of the finished coating  30 . The Sulfur S content forms Sulfides S 2  to improve machinability and lubrication of the coating  30 . 
         [0020]    Example Alloy 2 is based on a steel alloy in particular having Carbon C in the range of about 0.28 to about 0.35 weight percent wt %, Manganese Mn in the range of about 1.35 to about 1.65 wt %, Chromium Cr at about 0.50 wt % maximum, Molybdenum Mo at about 0.40 wt % maximum, Silicon Si in the range of about 0.50 to about 1.00 wt %, Aluminum Al in the range of about 1.10 to about 1.40 wt %, Titanium Ti at about 0.60 wt % maximum, Sulfur S in the range about 0.24 to about 0.33 wt %, and Phosphorus P at about 0.03 wt % maximum, with the balance Iron Fe. More specifically, the Carbon C content is prescribed to improve strength and overcome cracking of the finished coating  30 . Aluminum Al and Titanium Ti content is prescribed to tailor oxides formed in the thermal spraying process. The Aluminum oxide Al 2 O 3  and Titanium oxide TiO 2  aid in the wear and friction properties of the finished coating  30 . The Sulfur S content forms Sulfides S 2  to improve machinability and lubrication of the coating  30 . 
         [0021]    Example Alloy 3 is based on a steel alloy in particular having Carbon C in the range of about 0.25 to about 0.30 weight percent wt %, Manganese Mn in the range of about 1.35 to about 1.65 wt %, Silicon Si in the range of about 0.50 to about 1.00 wt %, Aluminum Al in the range of about 1.10 to about 1.40 wt %, Sulfur S in the range about 0.24 to about 0.33 wt %, and Phosphorus P at about 0.03 wt % maximum, with the balance Iron Fe. More specifically, the Carbon C content is prescribed to improve strength and overcome cracking of the finished coating  30 . Aluminum Al content is prescribed to tailor oxides formed in the thermal spraying process. The Aluminum oxide Al 2 O 3  aid in the wear and friction properties of the finished coating  30 . The Sulfur S content forms Sulfides S 2  to improve machinability and lubrication of the coating  30 . 
         [0022]    Example Alloy 4 is based on a stainless steel alloy in particular having Carbon C in the range of about 0.10 to about 0.60 weight percent wt %, Manganese Mn in the range of about 1.00 to about 2.00 wt %, Chromium Cr in the range of about 8.00 to about 30.00 wt %, Molybdenum Mo at about 3.00 wt % maximum, Silicon Si in the range of about 0.30 to about 1.50 wt %, Aluminum Al in the range of about 0.40 to about 3.00 wt %, Titanium Ti at about 1.00 wt % maximum, Sulfur S in the range about 0.10 to about 0.33 wt %, and Nickle Ni at about 14.00 wt % maximum, with the balance Iron Fe. More specifically, the Carbon C content is prescribed to improve strength and overcome cracking of the finished coating  30 . Aluminum Al and Titanium Ti content is prescribed to tailor oxides formed in the thermal spraying process. The Aluminum oxide Al 2 O 3  and Titanium oxide TiO 2  aid in the wear and friction properties of the finished coating  30 . The Sulfur S content forms Sulfides S 2  to improve machinability and lubrication of the coating  30 . 
         [0023]    While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and examples for practicing the invention within the scope of the appended claims.