1、Good wear resistance
In the QPQ process, the metal material reacts with the salt bath liquid at a working temperature of 570±10℃ to form a dense compound layer of excellent quality on the metal surface. The compound consists entirely of epsilon iron nitride, which is highly effective in improving the hardness and denseness of the metal surface, resulting in good wear resistance. The hardness value of the treated metal surface depends on the alloying elements in the steel, and the higher the content of alloying elements, the higher the hardness of the layer. According to the level of hardness of the seepage layer, the commonly used materials can be divided into the following major categories.
(1) carbon steel, low Taikin steel
Representative steel grades: 20, 45, TiO, 20Cr, 40Cr, etc. Infiltration layer surface hardness: 500-700HV
Representative steel grades: 3CrW8V, Crl2MoV, 38CrMoAl, 1Crl3-4Cr13, etc. Infiltration layer surface hardness: 850-1000HV
(3) high-speed steel, austenitic stainless steel Representative steel: quenched Wl8Cr4V, W6Mo5Cr4V2 and 1Crl8Ni9Ti, etc. Seepage layer surface hardness: 1000-1250HV
(4) cast iron seepage layer surface hardness: >500HV
The following chart is the sliding wear test data of 40Cr material workpiece after different treatment methods, with the wear value of QPQ 0.22mg as the benchmark, the wear resistance of QPQ process is 2.1 times of hard chromium plating, 2.8 times of ion nitriding, 23.7 times of high frequency quenching and 29.4 times of conventional quenching.
2、Good corrosion resistance
The following chart shows the neutral salt spray test comparison of 45# steel after QPQ salt bath composite process, decorative chrome plating, hard chrome plating and ordinary blackening treatment with 1Cr18Ni9Ti stainless steel and 1Cr13 material. It can be seen that the corrosion resistance of 45# steel after QPQ treatment is 5 times that of 1Cr18Ni9Ti stainless steel, 70 times that of hard chromium plating, and 280 times that of ordinary blackening. Other materials after QPQ process treatment, neutral salt spray test can reach 100-300 hours.
3、Good fatigue resistance
After QPQ salt bath composite process after the introduction of the metal surface and produce a very high residual compressive stress, the result leads to greatly improve the fatigue strength of various types of fatigue resistance, after testing proved to improve the fatigue strength of about 100%, slow pitting, rust and other surface defects.
4、Very small deformation
QPQ salt bath composite treatment technology due to the process temperature is low, below the phase change point of the steel, no tissue transformation will occur, therefore, compared with the quenching, high-frequency quenching, carburizing quenching and carbonitriding and other hardening processes that produce huge tissue stress, the deformation of the workpiece after treatment is much smaller. At the same time, because after nitriding at 570-580 ℃, the workpiece should be held at 350-400 ℃ for 15-20 min, which will greatly reduce the thermal stress generated when the workpiece is cooled, so the QPQ salt bath composite process is almost no deformation of the workpiece after treatment, is the smallest deformation of the hardening technology, can Effective solution to the conventional heat treatment methods difficult to solve the problem of hardening deformation.
5、Low carbon and environmental protection
The German company Digoxa, which invented the process, won the German environmental protection award for this process. In China, the QPQ treatment process has been tested and identified by the relevant environmental protection departments and proven to be harmless, pollution-free and free of heavy metals by the actual use of users across the country. And used to replace some of the more polluting processes such as electroplating.
6、It can replace multiple processes and reduce the time cost
Metal materials after QPQ salt bath composite process, in order to improve its hardness and wear resistance at the same time also improve its corrosion resistance, so it can replace the conventional quenching (ion nitriding, high-frequency quenching, etc.) a tempering a blackening (chrome plating) and other multi-process, greatly shorten the production cycle, reduce production costs. A large number of production data show that QPQ treatment compared with carburizing quenching can save 50% of energy, compared with hard chrome plating cost savings of 30%, cost-effective.