Patent Publication Number: US-2019194786-A1

Title: Hardfacing Material

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the technology field of alloy materials, and more particularly to a hardfacing material. 
     2. Description of the Prior Art 
     Surface treatment or modification technologies are widely adopted for forming a coating layer onto the surface of a workpiece, so as to extend the workpiece&#39;s service time. Hardfacing process is one kind of surface modification technology and used for coating a hardfacing material onto a workpiece&#39;s surface by thermal spraying, meltallizing, build-up welding, or sintering. After covering the surface of the workpiece by the hardfacing material, mechanical characteristics like wear resistance, corrosion resistance and/or thermal resistance of the workpiece&#39;s surface are then improved, such that service time of the workpiece would be obviously extended. 
     Conventional hardfacing material is commonly a Fe-based, Co-based or Ni-based alloy containing with other additional elements such as Cr, V, and/or Mo for enhancing corrosion resistance and thermal stability thereof. It is worth noting that, development and applications of the hardfacing alloy are found to be limited due to the fact that the composition design of the hardfacing alloy usually uses Fe, Co, or Ni as a principal element for forming the base alloy structure. As a result, workpieces coated with different surface modification layers made of various conventional hardfacing materials are unable to satisfy requirements of environments implemented with the workpieces. For instance, Ni-based and Co-based hardfacing alloys exhibit wear resistance and thermal stability superior than Fe-based hardfacing alloys, however, the Fe-based hardfacing alloys are low-cost surface modification materials having the outstanding mechanical strength. 
     From above descriptions, it is understood that the target application environments or workpieces of a hardfacing alloy should be firstly considered when designing and developing the hardfacing alloy. For example, by selecting proper materials for forming a base alloy structure and simultaneously making the base alloy structure contain at least one precipitation-strengthened alloy structure, a corresponding hardfacing material suitable for being processed to a surface modification layer on a specific workpiece is hence completed. Moreover, the specific workpiece having the particularly-developed surface modification layer is able to satisfy requirements of its application environment. 
     Differing from the fact that traditional or conventional alloys often contain one principal metal element, a new design concept of high-entropy alloys (HEAs) has been disclosed by literature 1. Literature 1, written by Yeh et. al (hereinafter “Yeh”), is entitled with “Nanostructured High-entropy Alloys with Multi-Principal Elements—Novel Alloy Design Concepts and Outcomes” and published on ADVANCED ENGINEERING MATERIALS 6(5)(2004), pp. 299-303). Particularly, Yeh defined that a high-entropy alloy must contain at least five principal elements with the concentration of each element being between 35 and 5 at %. According to the definition of HEAs described in literature 1, there are countless compositions for synthesizing HEAs. For instance, there are 1716 combinations of element from 5 elements to 13 elements for constructing 1716 HEA systems when 13 elements are chosen. In each alloy system, different compositions with concentrations in euiatomic or non-equiatomic ratio could be designed for synthesizing HEAs of the HEA system. 
     The so-called high entropy alloy (HEA) can benefit from the high entropy strengthening effects and show the advantages in lower density and lower cost of materials due to less refractory additions. In addition, the experimental results have indicated that HESA possess good microstructure stability, hot corrosion and oxidation resistance, as well as high hardness, tensile and creep strength at elevated temperatures. Thus, based on literature 1&#39;s basic principle, inventors of the present application have made great efforts to make inventive research thereon and eventually provided a hardfacing material. 
     SUMMARY OF THE INVENTION 
     The primary objective of the present invention is to provide a kind of hardfacing alloy, which can be applied onto a workpiece&#39;s surface by any one surface treatment process in accordance with material, dimensions, and required properties of the workpiece. For example, this novel hardfacing material can be heated to a fully melted state or a partially melted state by using different types of heat sources, such that the melted hardfacing material can be coated onto the surface of any one workpiece to form a protective layer or a surface modification layer. As a result, the workpiece having the surface coating layer with superior characteristics exhibits outstanding functional performances and has a long service time. 
     In order to achieve the primary objective of the present invention, the inventor of the present invention provides an embodiment for the hardfacing material, comprising:
         at least four principal metal elements, being selected from the group consisting of Al, Co, Cr, Cu, Fe, Mn, Mo, Ni, Nb, Ti, Ta, V, W, and Zr, and a first summation mole number of the principal metal elements is 50-90 percent of a total mole number of the hardfacing material; and   at least one non-metal element, being selected from the group consisting of B, C, N, O, and Si, and a second summation mole number of the non-metal element is 5-50 percent of the total mole number of the hardfacing material;   wherein two of the at least four principal metal elements are selected from the group consisting of Al, Cr, Mo, Nb, Ti, Ta, V, W, and Zr;   wherein each of the principal metal elements have a mole number of principal metal element, and the mole number of principal metal element is equal to or greater than 5 percent of the first summation mole number.       

     In the embodiment of the hardfacing material, wherein the principal metal elements and the at least one non-metal element form at least one base alloy structure and at least one precipitation-strengthened alloy structure of the hardfacing material. 
     In the embodiment of the hardfacing material, wherein a product or a semi-product of the hardfacing material can be a powder, a wire, a welding rod, a cored wire, or a bulk. 
     In the embodiment of the hardfacing material, wherein the hardfacing material is able to be coated on the surface of a target workpiece by a surface modification process selected from the group consisting of: meltallizing, build-up welding, thermal spraying, and sintering. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention as well as a preferred mode of use and advantages thereof will be best understood by referring to the following detailed description of an illustrative embodiment in conjunction with the accompanying drawings, wherein: 
         FIG. 1  shows an SEM image of a first best embodiment of a hardfacing material according to the present invention; 
         FIG. 2  shows an SEM image of a second best embodiment of the hardfacing material; 
         FIG. 3  shows an SEM image of a third best embodiment of the hardfacing material; and 
         FIG. 4  shows an SEM image of a fourth best embodiment of the hardfacing material. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     To more clearly describe a hardfacing material according to the present invention, embodiments of the present invention will be described in detail with reference to the attached drawings hereinafter. 
     Traditional hardfacing alloys often contain one kind of primary elemental composition; for example, Fe-based, Co-based or Ni-based hardfacing alloy containing with other additional elements such as Cr, V, and/or Mo for enhancing corrosion resistance and thermal stability thereof. Particularly, the present invention discloses a hardfacing material comprises at least four principal metal elements at least four principal metal elements and at least one non-metal element, wherein the principal metal elements and the at least one non-metal element form at least one base alloy structure and at least one precipitation-strengthened alloy structure of the hardfacing material. It needs to further explain that, at least four principal metal elements are selected from the group consisting of Al, Co, Cr, Cu, Fe, Mn, Mo, Ni, Nb, Ti, Ta, V, W, and Zr; more particularly, two of the at least four principal metal elements are selected from the group consisting of Al, Cr, Mo, Nb, Ti, Ta, V, W, and Zr. 
     On the other hand, the at least one non-metal element, being selected from the group consisting of B, C, N, O, and Si, and a second summation mole number of the non-metal element is 5-50 percent of the total mole number of the hardfacing material. According to the present invention, a first summation mole number of the principal metal elements is 50-90 percent of a total mole number of the hardfacing material, and a second summation mole number of the non-metal element is 5-50 percent of the total mole number of the hardfacing material. Moreover, each of the principal metal elements have a mole number of principal metal element, and the mole number of principal metal element is equal to or greater than 5 percent of the first summation mole number. 
     Moreover, for proving the practicability of the hardfacing material of the present invention, inventors of the present invention have completed a variety of experiments. 
     First Experiment: Finding Out Proper Content of Elements for Constituting the Hardfacing Material 
     Following Table (1) and Table (2) record related data of the first experiment. From the two tables, it is found that Cr, Fe, Mn, and Ni are adopted for being as the principal metal elements contained by samples of the hardfacing material, wherein the hardfacing material further comprises strengthening elements of Al and Mo for forming precipitation-strengthened alloy structure of the hardfacing material. On the other hand, B and C are adopted for being as the non-metal elements in the samples. Based on the experimental data, it is understood that the hardness and the wear resistance of the samples 1-4 increase with the growth of the non-metal element&#39;s content. It is worth noting that, the growing content of the non-metal element&#39;s (i.e., the increasing hardness of the hardfacing material) must causes the hardfacing material&#39;s tenacity decline. As a result, owing to lack of tenacity, the hardfacing material may be subject to cracks or break when being implemented in an application environment. Therefore, based on the data of the first experiment, the inventors have confirmed the elements and content thereof for constituting the hardfacing material, which are summarized as follows:
         (1) a first summation mole number (FSMN) of the principal metal elements (ME) is 64-85 percent of a total mole number of the hardfacing material; and   (2) a second summation mole number (SSMN) of the non-metal element (nME) is 15-36 percent of the total mole number of the hardfacing material.       

     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE (1) 
               
               
                   
               
               
                   
                 ME1 
                 ME2 
                 ME3 
                 ME4 
                 ME5 
                 ME6 
                 nME 
                   
               
               
                 Sample 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 Hardness 
               
               
                   
               
             
            
               
                 1 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                 B 
                 HV521  
               
               
                   
                 2.9 
                 24   
                 38.3 
                 9.6 
                 5   
                 1   
                 19.2 
               
               
                 2 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                 B 
                 HV1041 
               
               
                   
                 1.6 
                 13.5 
                 45.5 
                 5.4 
                 4.2 
                 0.6 
                 29.2 
               
               
                 3 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                 B 
                 HV1258 
               
               
                   
                 1.5 
                 12.9 
                 43.3 
                 5.2 
                 4.1 
                 0.5 
                 32.5 
               
               
                 4 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                 B 
                 HV1436 
               
               
                   
                 1.5 
                 12.3 
                 41.3 
                 4.9 
                 4.0 
                 0.5 
                 35.6 
               
               
                 5 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                 C 
                 HV841  
               
               
                   
                 3.4 
                 46   
                 17.2 
                 11.5  
                 5.7 
                 1.1 
                 14.9 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE (2) 
               
               
                   
               
               
                 FSMN 
                 ME1 
                 ME2 
                 ME3 
                 ME4 
                 ME5 
                 ME6 
                 nME 
                 SSMN 
               
               
                 (%) 
                 (%) 
                 (%) 
                 (%) 
                 (%) 
                 (%) 
                 (%) 
                 (%) 
                 (%) 
               
               
                   
               
             
            
               
                 80.8 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                 B 
                 19.2 
               
               
                   
                 3.59 
                 29.7  
                 47.4  
                 11.88 
                 6.19 
                 1.24 
                 19.2 
               
               
                 70.8 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                 B 
                 29.2 
               
               
                   
                 2.26 
                 19.07 
                 64.25 
                  7.63 
                 5.93 
                 0.85 
                 29.2 
               
               
                 67.5 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                 B 
                 32.5 
               
               
                   
                 2.22 
                 19.11 
                 64.15 
                 7.7 
                 6.07 
                 0.74 
                 32.5 
               
               
                 64.5 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                 B 
                 35.5 
               
               
                   
                 2.33 
                 19.0  
                 64.0  
                 7.6 
                 6.2  
                 0.78 
                 35.5 
               
               
                 84.9 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                 C 
                 14.9 
               
               
                   
                 4   
                 54.18 
                 20.26 
                 13.55 
                 6.71 
                 1.3  
                 14.9 
               
               
                   
               
            
           
         
       
     
     From Table (2), it is also known that, each of the principal metal elements (Al, Cr, Fe, Mn, Mo, and Ni) have a mole number of principal metal element, and the mole number of principal metal element is equal to or greater than 5 percent of the first summation mole number (FSMN). Moreover, engineers skilled in development and manufacture of hardfacing alloys must know that, target application environments or workpieces of a specific hardfacing material should be firstly considered when designing and developing the hardfacing material. For example, by selecting proper materials for forming a base alloy structure and simultaneously making the base alloy structure contain at least one precipitation-strengthened alloy structure, a corresponding hardfacing material suitable for being processed to a surface modification layer on a specific workpiece is hence completed. Therefore, the specific workpiece having the particularly-developed surface modification layer is able to satisfy requirements of its application environment. On the other hand, it needs to further explain that a product or a semi-product of the hardfacing material proposed by the present invention can be a powder, a wire, a welding rod, a cored wire, or a bulk. Moreover, the hardfacing material is able to be coated on a target workpiece&#39;s surface by any one type of surface modification process, such as meltallizing, build-up welding, thermal spraying, or sintering. 
     Second Experiment: Understanding the Characteristics of the Hardfacing Materials with Different Alloy Systems 
     Following Table (3) records related data of the second experiment. From the Table (3), it is found that Al, Co, Cr, Cu, Fe, and Ni are adopted for being as the principal metal elements contained by samples 6-7 of the hardfacing material, wherein Al and Cr are elements belong to precipitation-strengthened alloy structure of the hardfacing material. On the other hand, Co, Cr, Fe, Ni, and Ti are adopted for being as the principal metal elements (ME) contained by samples 8-9 of the hardfacing material, wherein Cr and Ti are elements belong to precipitation-strengthened alloy structure of the hardfacing material. Moreover, B and C are adopted for being as the non-metal elements (nME) in the four samples. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE (3) 
               
               
                   
               
               
                   
                 ME1 
                 ME2 
                 ME3 
                 ME4 
                 ME5 
                 ME6 
                 nME 
                   
               
               
                 Sample 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 Hardness 
               
               
                   
               
             
            
               
                 6 
                 Al 
                 Co 
                 Cr 
                 Cu 
                 Fe 
                 Ni 
                 B 
                 HV523 
               
               
                   
                  7.8 
                 15.5 
                 15.3 
                 15.4 
                 15.5 
                 15.2 
                 15.3 
               
               
                 7 
                 Al 
                 Co 
                 Cr 
                 Cu 
                 Fe 
                 Ni 
                 B 
                 HV774 
               
               
                   
                  6.7 
                 13.3 
                 13.5 
                 13.2 
                 13.3 
                 13   
                 27   
               
               
                 8 
                 Co 
                 Cr 
                 Fe 
                 Ni 
                 Ti 
                   
                 C 
                 HV721 
               
               
                   
                 15.6 
                 12.1 
                 10.5 
                 15.3 
                 33.3 
                   
                 13.2 
               
               
                 9 
                 Co 
                 Cr 
                 Fe 
                 Ni 
                 Ti 
                   
                 C 
                  HV1015 
               
               
                   
                 13.5 
                  9.7 
                  8.8 
                 13.4 
                 29.7 
                   
                 24.9 
               
               
                   
               
            
           
         
       
     
     Table (4) also records related data of the second experiment. From the Table (4), samples 10-11 of the hardfacing material contains elements of Al, Cr, Ti, and Zr for forming precipitation-strengthened alloy structure of the hardfacing material. Moreover, B and Si are adopted for being as the non-metal elements in the two samples. On the other hand, samples 12-13 of the hardfacing material contains elements of Al, Cr, Ta, Ti, and Zr for forming precipitation-strengthened alloy structure of the hardfacing material. Moreover, O and N are adopted for being as the non-metal elements in the two samples. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
             
               
                   
                 TABLE (4) 
               
               
                   
                   
               
               
                   
                 ME1 
                 ME2 
                 ME3 
                 ME4 
                 ME5 
                 ME6 
                 nME 
                 nME 
                   
               
               
                   
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 Hardness 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 10 
                 Al 
                 Cr 
                 Fe 
                 Ni 
                 Ti 
                 Zr 
                 B 
                 Si 
                 HV745  
               
               
                   
                 12.4 
                 12.3 
                 12.7 
                 12.5 
                 12.5 
                 12.5 
                 12.5 
                 12.5 
               
               
                 11 
                 Al 
                 Cr 
                 Fe 
                 Ni 
                 Ti 
                 Zr 
                 B 
                 Si 
                 HV850  
               
               
                   
                 13.3 
                 13.3 
                 13.3 
                 13.3 
                 13.3 
                 13.3 
                  6.7 
                 13.3 
               
               
                 12 
                 Al 
                 Cr 
                 Ta 
                 Ni 
                 Zr 
                   
                 O 
                   
                 HV1800 
               
               
                   
                 15.3 
                 15.5 
                 15.4 
                 15.7 
                 15.1 
                   
                 23   
               
               
                 13 
                 Al 
                 Cr 
                 Ta 
                 Ti 
                 Zr 
                   
                 N 
                   
                 HV1500 
               
               
                   
                 15.5 
                 15.7 
                 14.4 
                 14.5 
                 16.8 
                   
                 13.1 
               
               
                 14 
                 Al 
                 Cr 
                 Ta 
                 Ti 
                 Zr 
                   
                 C 
                 N 
                 HV1500 
               
               
                   
                 12.2 
                 14.2 
                  8.9 
                 10.8 
                 10.3 
                   
                 15.8 
                 27.8 
               
               
                   
               
            
           
         
       
     
     The Best Alloy Systems for Fabricating the Hardfacing Materials 
     Following Table (5) and Table (6) list constituting elements and their atomic percent for fabricating best embodiment(s) of the hardfacing material proposed by the present invention. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
             
               
                   
                 TABLE (5) 
               
               
                   
                   
               
               
                   
                 ME1 
                 ME2 
                 ME3 
                 ME4 
                 ME5 
                 ME6 
                 ME7 
                 nME 
                   
               
               
                   
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 (at %) 
                 Hardness 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 I 
                 Al 
                 Cr 
                 Mn 
                 Fe 
                 Ni 
                 Mo 
                   
                 C 
                 HV785 
               
               
                   
                 3.4 
                 46   
                 11.5 
                 17.6 
                 5.7 
                 1.1 
                   
                 14.7 
               
               
                 II 
                 Al 
                 Cr 
                 Mn 
                 Fe 
                 Ni 
                 Mo 
                   
                 B 
                 HV737 
               
               
                   
                 3.7 
                 47.2 
                 11.8 
                 17.2 
                 5.9 
                 1.3 
                   
                 12.9 
               
               
                 III 
                 Al 
                 Cr 
                 Mn 
                 Fe 
                 Ni 
                 Mo 
                 Nb 
                 C 
                 HV810 
               
               
                   
                 3.4 
                 44.2 
                 11.0 
                 16.6 
                 5.5 
                 1.1 
                 3.3 
                 14.9 
               
               
                 IV 
                 Al 
                 Cr 
                 Mn 
                 Fe 
                 Ni 
                 Mo 
                 Ti 
                 B 
                 HV765 
               
               
                   
                 3.1 
                 41.7 
                 10.4 
                 15.6 
                 5.2 
                 1.0 
                 6.3 
                 16.7 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE (6) 
               
               
                   
               
               
                 FSMN 
                 ME1 
                 ME2 
                 ME3 
                 ME4 
                 ME5 
                 ME6 
                 ME7 
                 SSMN 
               
               
                 (%) 
                 (%) 
                 (%) 
                 (%) 
                 (%) 
                 (%) 
                 (%) 
                 (%) 
                 (%) 
               
               
                   
               
             
            
               
                 85.3 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                   
                 C 
               
               
                   
                 3.99 
                 53.93 
                 20.63 
                 13.48 
                 6.68 
                 1.29 
                   
                 14.7 
               
               
                 87.1 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                   
                 B 
               
               
                   
                 4.25 
                 54.19 
                 19.35 
                 13.55 
                 6.77 
                 1.49 
                   
                 12.9 
               
               
                 85.1 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                 Nb 
                 C 
               
               
                   
                 4.0  
                 51.94 
                 19.51 
                 12.93 
                 6.46 
                 1.29 
                 3.88 
                 14.9 
               
               
                 83.3 
                 Al 
                 Cr 
                 Fe 
                 Mn 
                 Ni 
                 Mo 
                 Nb 
                 B 
               
               
                   
                 3.72 
                 50.06 
                 18.73 
                 12.48 
                 6.24 
                 1.20 
                 6.3  
                 16.7 
               
               
                   
               
            
           
         
       
     
       FIG. 1 - FIG. 4  show SEM images of a first best embodiment, a second best embodiment, a third best embodiment, and a fourth best embodiment of the hardfacing material, respectively. Information of symbols I, II, III, and IV are provided in following Table (7). 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE (7) 
               
               
                   
               
               
                 I 
                 II 
                 III 
                 IV 
                 V 
               
               
                   
               
             
            
               
                 Light-gray 
                 Deep-gray 
                 Deep colour 
                 White 
                 Black carbide 
               
               
                 base phase 
                 base phase 
                 carbide 
                 carbide 
                 (or boride) 
               
               
                 structure 
                 structure 
                 (or boride) 
               
               
                   
               
            
           
         
       
     
     From the provided SEM images, it is found that each of the best embodiments of the hardfacing material comprise at least one base phase structure and at least two compound phase structures, wherein the compound phase is regarded as precipitation-strengthened alloy structure of the hardfacing material. Therefore, the hardfacing material of the present invention can be coated on a target workpiece&#39;s surface, so as to enhance mechanical characteristics of the workpiece such as wear resistance, corrosion resistance and/or thermal resistance. it needs to further explain that a product or a semi-product of the hardfacing material proposed by the present invention can be a powder, a wire, a welding rod, a cored wire, or a bulk. Moreover, the hardfacing material is able to be coated on a target workpiece&#39;s surface by any one type of surface modification process, such as meltallizing, build-up welding, thermal spraying, or sintering. 
     For instance, it is able to dispose powdered hardfacing material onto the target workpiece&#39;s surface, and then transmit the workpiece into a heating furnace, such that a protect layer made of the hardfacing material is formed on the workpiece&#39;s surface through sintering process. 
     Therefore, through above descriptions, the hardfacing material of the present invention have been introduced completely and clearly; in summary, the present invention includes the advantages of: 
     (1) The present invention discloses a kind of hardfacing alloy, which can be applied onto a workpiece&#39;s surface by any one surface treatment process in accordance with material, dimensions, and required properties of the workpiece. For example, this novel hardfacing material can be heated to a fully melted state or a partially melted state by using different types of heat sources, such that the melted hardfacing material can be coated onto the surface of any one workpiece to form a protective layer or a surface modification layer. As a result, the workpiece having the surface coating layer with superior characteristics exhibits outstanding functional performances and has a long service time. 
     The above description is made on embodiments of the present invention. However, the embodiments are not intended to limit scope of the present invention, and all equivalent implementations or alterations within the spirit of the present invention still fall within the scope of the present invention.