Do you wanted to know the exact process of the case hardening?好，keep reading this article to have an exact information about the case hardening.So,what are you waiting for?我们开始吧。
有些人可能会混淆表面硬化和表面硬化，但你知道这两个术语完全相似。But you may have a question that what is the definition It.所以，让我们继续寻找它。
Case hardening is the process through which metal surface is strengthened by covering the surface of the 亚博体育官方下载workpiece by the layer of another harder material and this layer is more durable.
There are certain metals like iron or steel,硬度很低。在这种情况下，表面硬化在金属表面产生一层氮或碳。And this layer provides greater hardness than the original surface of the metal.
Different Process of Case Hardening
There are different processes of case hardening
Carburizing is one of the types of the heat treatment processes and it is also called as the carburization.在渗碳技术中，the metal is heated in the presence of the charcoal or carbon-monoxide.Do you know the purpose of the carburizing?The only purpose of the carburizing is to make the metal harder by heating it in a very short interval of time.在渗碳过程中，使用各种硬化金属，如一氧化碳，Barium carbonate,Sodium Cyanide,etc.
After completing the carburizing,you may see the changes in the size and shape of the original metal.但与其他热处理工艺相比，这些变化非常小。
Nitriding is one of the heat treatment processes in which the nitrogen spreads over the surface of the metal to form its layer on the surface of the metal.Thus,渗氮是表面硬化的一部分。It is used mostly in case of steels that contain low carbon content.之前的声明有一些例外，如钛和钼。渗氮在齿轮制造中的应用非常广泛，injectors,screws,camshafts and various tools.
Nitriding is again further divided into three main processes like:
(i) Plasma Nitriding
等离子渗氮主要用于工业应用。Plasma nitriding is also termed as ion nitriding or glow-discharge nitriding.In plasma nitriding,an effective electric field is generated which results in ionization of the gas molecules.In the entire process of the plasma nitriding,nitrogen is used.It is the perfect process for treating steels.德国的BernhardtBerghus博士发明了等离子渗氮。
- Not only the durability of the metal parts increases but its performance also increases.
Sometimes,Physical Vapour Deposition (VPD) combines with the plasma nitriding to get more benefits of the process.等离子渗氮工艺在260-600的温度范围内进行。γC.The plasma nitriding does not depend on any type of temperature that's why we have selected such a broad range of temperature.例如，stainless steel is nitrated at the temperature of about 420γc不会形成任何类型的沉淀物，也不会干扰任何腐蚀电阻率。
In the plasma nitriding process,along with the nitrogen certain amount of hydrogen and argon are also used.
为了进一步了解等离子渗氮的方法，watch the video given below:
(ii) Gas Nitriding
In gas nitriding,ammonia is used.During gas nitriding,ammonia comes in contact with heated metal and this ammonia separates into hydrogen and nitrogen.The nitrogen formed then spread on the surface of the metal forming nitride layer.Following are the benefits of the gas nitriding:
As every coin has two sides,gas nitriding has advantages as well as disadvantages.So,气体渗氮的缺点如下：
- As ammonia is used in this process it can be really hazardous if inhaled in large quantities.
(iii) Salt Bath Nitriding
在这里，the cyanide salt plays an important role in the salt bath nitriding.The temperature is between the 550-570γC.盐浴贸易中最有利的部分是，在同一时间间隔内，氰化物盐在比任何其他工艺更大的表面积上的扩散。
这个过程很快完成，只需要4个小时。Along with the quick process,这一过程还涉及其他并发症。
Some of the demerits of using this salt bath nitriding are as follows:
- 在这里，in salt bath nitriding we use some toxic salts that can affect our lives.
- The cost of practicing salt bath nitriding is much more than other heat treatment processes.
Following are the steels on which nitriding can be easily done:
- SAE 4100
- BS 4S 106
- BS 3S 132
Carbonitriding is the type of the case hardening process in which the hardness of the metal surface is increased and also any type of deformation is also reduced during this process.顾名思义，in carbonitriding,the carbon and nitrogen atoms spread over the metal surface and results in increasing the hardness of the metal.碳氮共渗在800以上γC.由于碳氮共渗而在工件上形成的层相当坚硬。亚博体育官方下载This layer is of average thickness ranging from 0.07 mm to 0.5 mm.The maximum thickness of the layer that can be formed is 0.75 mm.
Following are the advantages of the carbonitriding that you must know
碳氮共渗用于轴承，dies,various shafts,fastener pins,etc.
It is also one of the case hardening processes in which the metal is heated in the temperature range of 871 to 954γC.在这里，the metal part is heated in the presence of the sodium cyanide.Cyaniding results in the formation of layer of thickness ranging from 0.25 mm to 0.75 mm.这种工艺通常适用于低碳钢。Also,与其他流程不同，它只需要20到30分钟。Its application is found on metallic parts such as gears,screws,小坚果，etc.The disadvantage of this process is that here the cyanide salt is used and this cyanide salt is very poisonous and this hazardous to our life.在另一边，its advantage is that it is efficient and fast process.
Ferric nitrocarburizing is one of the case hardening process in which the carbon and nitrogen are spread out on the ferrous metals.
History Behind Ferric Nitrocarburizing:
铁氮碳共渗首先由英国帝国化学工业（ICI）实施。ICI called this process as a Sulfinuz treatment.There were a lot of issues with this process.Later,1950，Joseph Lucas Limited Company implemented this case hardening process successfully.Ferric nitrocarburizing is carried out at the sub-critical temperatures during the process of the salt bath.This process is practiced mostly in the temperature range of the 525γC to the 625º C.During such temperatures,钢和其他合金都处于铁素体相。铁氮碳共渗有助于改善金属的这三种性能：
- Yield strength of the metal
Ferric nitrocarburizing is further divided into following types:
(i) Salt Bath Ferritic Nitrocarburizing：
This process is often termed as liquid nitrocarburizing or sometimes as liquid ferric nitrocarburizing.这些过程有各种专有名称，如Tenifer或Tufftride。Salt bath ferritic nitrocarburizing is mostly used in case of cast irons and sintered irons.进行这一过程的主要重点是提高耐腐蚀性和减少摩擦。In this process,a solution of alkali cyanate is used.这种碱性氰酸盐与金属表面反应形成碳酸碱。碱氰酸盐与金属表面的反应形成了扩散层和复合层两种类型的层。Its tradename is Meli1.
Diffusion layer:The diffusion layer consists of the carbides as well as nitrides.
Compound layer:The compound layer consists of the iron,nitrogen and oxygen.The compound layer is very stable at room temperature.
在等离子铁素体氮碳共渗中，电场作用于电离气体分子，这些电离气体分子被用来扩散金属上的碳和氮。These highly ionised gas molecules are nothing but the plasma.This case hardening process is also termed as plasma ion nitriding or ion nitriding or glow-discharge nitriding.此过程在420的温度范围内进行。γC to 580γC.
(iii) Gaseous Ferritic Nitrocarburizing
气态铁素体也称为真空氮碳共渗或软氮化或控制氮碳共渗。It is also famous by tradenames like Nitroc,DeganitTriniding,Nitemper and Nitrotec.The gases that are used during this process are ammonia and other endothermic gases.This process takes place around one to four hours and at 570γC.In gaseous ferritic nitrocarburizing,通过蒸汽脱脂的过程清洁各个零件。
Following are the applications of the Ferric nitrocarburizing:
- Companies like Grandpower and Caracal International L.L.C.在各种应用中使用这种氮碳共渗。
在本文中，you have learnt about case hardening,the processes involved in case hardening.If you like this article then don't hesitate to share it maximum!！